Most cyanotic congenital heart defects (CHDs) manifest during the neonatal period, requiring a correct diagnosis for appropriate management. Detection of cyanosis has been made much easier in recent years by routine use of pulse oximetry in asymptomatic newborns. Pulse oximetry helps detect most cyanotic CHDs as well as some noncyanotic critical CHDs. Critical CHDs include defects that depend on the patency of the ductus arteriosus for survival, such as hypoplastic left heart syndrome (HLHS), aortic arch atresia, critical aortic stenosis (AS), pulmonary stenosis (PS) or atresia, tricuspid atresia, and others.
However, pulse oximetry cannot detect all cases of critical CHDs or cyanotic CHDs. Hypoxemia may not be present in some patients with HLHS, AS, and coarctation of the aorta (COA) before discharge from the hospital. In addition, not all cyanotic CHDs manifest with detectable hypoxemia in the nursery. For example, some patients with double outlet right ventricle (RV), Ebstein’s anomaly, and acyanotic tetralogy of Fallot (TOF) may not manifest with detectable hypoxemia in early days of life. Therefore, a negative test result does not exclude the possibility of serious heart defects.
Many investigators believe that pulse oximetry in newborns should be done after 24 hours of life and before hospital discharge and be taken in lower extremities to be able to detect defects with right-to-left ductal shunt and that the cutoff point of abnormal oxygen saturation be set at 95% or less. Arterial saturation is expected to be lower in high altitudes (especially above 5000 ft), but the cutoff point has not been established (Mahle et al, 2009).
Hypoxemia does not necessarily mean a heart defect is present; it may be caused by pulmonary disease or central nervous system (CNS) depression. After hypoxemia (or central cyanosis) is detected, the cause of hypoxemia must be determined.
Approach to a Cyanotic Neonate
Three common causes of central cyanosis (or hypoxemia) are cardiac disease, pulmonary disease, and CNS depression. Clinical findings often direct physicians to the correct system that causes cyanosis. Table 14-1lists some of the differentiating clinical findings of central cyanosis associated with the three common causes of cyanosis. Crying may improve the cyanosis caused by lung diseases or CNS depression; however, crying usually worsens cyanosis in patients with cyanotic heart defects.
Box 14-1 lists some of the traditional tools used in the investigation of cyanotic newborns. Some of the steps could be skipped when cardiology consultation is readily available, but they are discussed for the sake of completeness.
1. Electrocardiography (ECG) and chest radiography. Although the routine tools of cardiac evaluation (physical examination, ECG, and chest radiography) are not very helpful in diagnosing a specific cyanotic heart defect, these tools are often useful in reducing the diagnostic possibilities. Besides being cyanotic, a neonate may have dyspnea, tachypnea, abnormal heart sounds, heart murmurs, or abnormal peripheral pulses. A midline liver may be palpable (or seen on radiography). Chest radiography may show abnormal lung fields (e.g., increased vascularity, oligemic lung fields, or other abnormalities) and abnormal cardiac shadow (abnormal size or abnormal silhouette). The ECG findings may include abnormal rhythm and rate, abnormal QRS axis, atrial hypertrophy, or ventricular hypertrophy. The more of these abnormalities the patient has, the greater the chance of having CHDs. Cardiology consult should be considered at this time.
TABLE 14-1
CAUSES AND CLINICAL FINDINGS OF CENTRAL CYANOSIS
|
Systems |
Causes |
Clinical Findings |
|
CNS depression |
Perinatal asphyxia |
Shallow irregular respiration |
|
Pulmonary disease |
Parenchymal lung disease (e.g., hyaline membrane disease) |
Tachypnea and respiratory distress with retraction and expiratory grunting |
|
Cardiac disease |
Cyanotic CHD with right-to-left shunt |
Tachypnea usually without retraction |
CHD, congenital heart defect; CHF, congestive heart failure; CNS, central nervous system; PDA, patent ductus arteriosus; PPHN, persistent pulmonary hypertension of the newborn.
BOX 14-1 Suggested Steps in The Management of Cyanotic Newborns
1. Chest radiography
Chest radiography may reveal pulmonary causes of cyanosis and the urgency of the problem.
It can also hint at the presence or absence of cardiac defects and the type of defect.
2. ECG if cardiac origin of cyanosis is suspected.
3. Arterial blood gases in room air
Arterial blood gases in room air confirm or reject central cyanosis.
An elevated PCO2 suggests pulmonary or CNS problems.
A low pH may be seen in sepsis, circulatory shock, or severe hypoxemia.
4. Hyperoxitest: Repeating arterial blood gases while the patient breathes 100% oxygen helps separate cardiac causes of cyanosis from pulmonary or CNS causes.
5. Umbilical artery line: A Po2 value in a preductal artery (e.g., the right radial artery) that is 10 to 15 mm Hg higher than that in a postductal artery (an umbilical artery line) suggests a right-to-left ductal shunt.
6. PGE1: If a cyanotic defect is suspected that depends on the patency of the ductus for survival, PGE1 (Prostin VR Pediatric) should be started or made available.
CNS, central nervous system; ECG, electrocardiography; PGE1, prostaglandin E1.
2. Hyperoxitest. This test helps differentiate cyanosis caused by cardiac disease from that caused by pulmonary diseases. When central cyanosis has been confirmed by arterial Po2, one tests the response of arterial Po2 to 100% oxygen inhalation (hyperoxitest). Oxygen should be administered through a plastic hood (e.g., an Oxyhood) for at least 10 minutes to completely fill the alveolar space with oxygen. With pulmonary disease, arterial Po2 usually rises to greater than 100 mm Hg. When there is a significant intracardiac right-to-left shunt, the arterial Po2 does not exceed 100 mm Hg, and the rise is usually not more than 10 to 30 mm Hg (see Chapter 11 for details). Exceptions exist in patients with large pulmonary blood flow and those with severe lung pathology.
3. Arterial Po2 in preductal and postductal arteries. It is important that one obtain arterial blood samples from the right upper body (right radial, brachial, or temporal artery), rather than from the descending aorta, to detect (true) cyanotic CHDs. If a low arterial Po2 is obtained from an umbilical artery line (or from a lower extremity site), another sample from the right upper body should be obtained, and the Po2values from the two sites should be compared to see if there is a right-to-left ductal shunt. Arterial PO2 from the right radial artery that is 10 to 15 mm Hg higher than that from an umbilical artery catheter is significant. In severe cases of right-to-left ductal shunt, differential cyanosis may be noticeable, with a pink upper and a cyanotic lower body. Such a right-to left ductal shunt is caused not only by persistent pulmonary hypertension of the newborn (PPHN) but also by other serious cardiovascular conditions, including severe obstructive lesions of the left ventricle (LV) (e.g., severe AS) or aortic obstructive lesions (e.g., interrupted aortic arch, COA).
4. Prostaglandin E1 (PGE1) infusion. If a cyanotic CHD or a ductus-dependent cardiac defect (e.g., pulmonary atresia with or without ventricular septal defect [VSD], tricuspid atresia, HLHS, interrupted aortic arch, severe COA) is suspected or confirmed, a PGE1 (Prostin VR Pediatric) intravenous (IV) infusion should be started. At the same time, cardiology consultation should be requested on an urgent basis. The starting dose of Prostin is 0.05 to 0.1 μg/kg per minute administered in a continuous IV drip. When the desired effects (increased Po2, increased systemic blood pressure, improved pH) are achieved, the dose should be reduced step by step to 0.01 μg/kg per minute. When the initial starting dose has no effect, it may be increased up to 0.4 μg/kg per minute. Three common side effects of IV infusion of PGE1 are apnea (12%), fever (14%), and flushing (10%). Less common side effects include tachycardia or bradycardia, hypotension, and cardiac arrest.
Complete Transposition of the Great Arteries
Prevalence
Complete transposition of the great arteries (TGA) occurs in about 5% to 7% of all CHDs. It is more common in males than in females (male-to-female ratio of 3:1).
Pathophysiology
1. In complete TGA, the aorta arises anteriorly from the RV carrying desaturated blood to the body, and the pulmonary artery (PA) arises posteriorly from the LV carrying oxygenated blood back to the lungs. In the classic complete TGA, the aorta is located anteriorly and to the right (dextro) of the PA. This is why the prefix D is used and thus the condition is called D-transposition (D-TGA). (When the transposed aorta is located to the left of the PA, it is called L-transposition, to be discussed later in this chapter.)
2. The result of D-TGA is complete separation of the pulmonary and systemic circulations. This results in hypoxemic blood circulating throughout the body and hyperoxemic blood circulating in the pulmonary circuit, which is not compatible with survival (see Fig. 11-4). Defects that permit mixing of the two circulations (e.g., atrial septal defect [ASD], VSD, and patent ductus arteriosus [PDA]) are necessary for survival.
3. About half of these infants do not have associated defects other than a patent foramen ovale (PFO) or a small PDA (i.e., simple TGA).
4. In about 5% of the patients, left ventricular outflow tract (LVOT) obstruction (or subpulmonary stenosis) occurs. The obstruction may be dynamic or fixed. Dynamic obstruction of the LVOT, which occurs in about 20% of such patients, results from bowing of the interventricular septum to the left because of a high RV pressure. Anatomic (or fixed) subpulmonary stenosis or abnormal mitral chordal attachment rarely causes obstruction of the LVOT.
FIGURE 14-1 Cardiac findings of transposition of the great arteries. Heart murmur is usually absent, and the S2 is single in the majority of patients.
5. VSD is present in 30% to 40% of patients with D-TGA and may be located anywhere in the ventricular septum. A combination of VSD and significant LVOT obstruction (or PS) occurs in about 10% of all patients with D-TGA. Infants with TGA and VSD more commonly have associated defects than those without associated VSD. Such associated defects may include COA, interrupted aortic arch, pulmonary atresia, and an overriding or straddling of the atrioventricular (AV) valve.
Overriding is an abnormal relationship between the AV valve annulus and the ventricular septum. The AV valve annulus commits to both ventricular chambers, and it is the result of malalignment of the atria and ventricular septa. Straddling is present when the chordae tendineae insert into the contralateral ventricle through a septal defect. Type A straddling is a mild form in which the chordae insert near the crest of the ventricular septum. In type B, the insertion is along the ventricular septum. In type C straddling, the chordae insert into the free wall of the contralateral ventricle. Overriding and straddling may occur independently or coexist in the same valve.
Clinical Manifestations
History
1. History of cyanosis from birth is always present.
2. Signs of congestive heart failure (CHF) with dyspnea and feeding difficulties develop during the newborn period.
Physical Examination (Fig. 14-1)
1. Moderate to severe cyanosis is present, especially in large male newborns. Such an infant is tachypneic but without retraction unless CHF supervenes.
2. The S2 is single and loud. No heart murmur is heard in infants with an intact ventricular septum. An early or holosystolic murmur of VSD may be audible in less cyanotic infants with associated VSD. A soft midsystolic murmur of PS (LVOT obstruction) may be audible.
3. If CHF supervenes, hepatomegaly and dyspnea develop.
Laboratory Studies
1. Severe arterial hypoxemia usually with acidosis is present. Hypoxemia does not respond to oxygen inhalation. (See the discussion of the hyperoxitest in an early section of this chapter.)
2. Hypoglycemia and hypocalcemia are occasionally present.
Electrocardiography (Fig. 14-2)
1. Right ventricular hypertrophy (RVH) is usually present after the first few days of life. The QRS voltages and the QRS axis may be normal in many newborns with the defect. After 3 days of life, an upright T wave in V1 may be the only abnormality suggestive of RVH.
FIGURE 14-2 Electrocardiographic tracing from a 6-day-old male infant with complete transposition of the great arteries. The QRS axis is +140 degrees. Note the deep S waves in V5 and V6 and an upright T wave in V1 are consistent with right ventricular hypertrophy.
FIGURE 14-3 Posteroanterior view of the chest radiograph from a 2-month-old infant with complete transposition of the great arteries. Note the cardiomegaly (cardiothoracic ratio, 0.7), “egg-shaped” heart with narrow waist, and increased pulmonary vascular markings, which are characteristic of this condition.
2. Biventricular hypertrophy (BVH) may be present in infants with large VSD, PDA, or pulmonary vascular obstructive disease because all of these conditions produce an additional left ventricular hypertrophy (LVH).
3. Occasionally, right atrial hypertrophy (RAH) is present.
Radiography
1. Cardiomegaly with increased pulmonary vascularity is typically present.
2. An egg-shaped cardiac silhouette with a narrow, superior mediastinum is characteristic (Fig. 14-3).
Echocardiography
Two-dimensional echocardiography and color-flow Doppler studies usually provide all the anatomic and functional information needed for the management of infants with D-TGA.
1. In the parasternal long-axis view, the great artery arising from the posterior ventricle (LV) has a sharp posterior angulation toward the lungs, which suggests that this artery is the PA (Fig. 14-4, A). In contrast to the normal intertwining of the great arteries, the proximal portion of the great arteries runs parallel. Unlike in a normal heart, there is a fibrous continuity between the pulmonary and mitral valves, and subaortic conus is present. (In normal hearts, there is aortic–mitral fibrous continuity with subpulmonary conus.)
FIGURE 14-4 Parasternal echocardiographic views in complete transposition of the great arteries. A, In this parasternal long-axis view, the great arteries are seen in parallel alignment. The posterior artery is directed posteriorly, bifurcates into two branches, and is therefore a pulmonary artery (PA). There is a continuity between the pulmonary valve and the mitral valve. B, In the parasternal short-axis view, the aorta (AO) and the PA are seen in cross section as double circles. The aorta is anterior to and right of the PA. LV, left ventricle; RV, right ventricle. (From Snider AR, Serwer GA: Echocardiography in Pediatric Heart Disease. St. Louis, Mosby, 1990.)
2. In the parasternal short-axis view, the “circle and sausage” appearance of the normal great arteries is not visible. Instead, the great arteries appear as “double circles” (Fig. 14-4, B). The PA is in the center of the heart, and the coronary arteries do not arise from this great artery. The aorta is usually anterior and slightly to the right of the PA, and the coronary arteries arise from the aorta.
3. In the apical and subcostal five-chamber views, the PA (i.e., the artery that bifurcates) is seen to arise from the LV, and the aorta arises from the RV.
4. The status of atrial communication, both before and after balloon septostomy, is best evaluated in the subcostal view. Doppler examination and color-flow mapping should aid in the functional evaluation of the atrial shunt.
5. Frequently, associated defects such as VSD, LVOT obstruction (dynamic or fixed), or pulmonary valve stenosis are found. Subaortic stenosis or COA rarely occurs.
6. The coronary arteries can be imaged in most patients in the parasternal and apical views (Fig. 14-5).
Other Studies
Cardiac catheterization is performed only for the purpose of balloon atrial septostomy to improve mixing at the atrial level. Rarely, it is performed to look for associated anomalies such as abnormal coronary artery, collateral circulation, or a small aortic isthmus.
Natural History
1. Progressive hypoxia, acidosis, and heart failure result in death in the newborn period. Without surgical intervention, death occurs in 90% of patients before they reach 6 months of age.
2. Infants with an intact ventricular septum are the sickest group but demonstrate the most dramatic improvement after Rashkind balloon atrial septostomy.
3. Infants with VSD are the least cyanotic group but the most likely to develop CHF and pulmonary vascular obstructive disease. Many infants with TGA and a large VSD develop moderate pulmonary vascular obstructive disease by 3 to 4 months of age. Thus, surgical procedures are recommended before that age.
4. Infants with a significant PDA are similar to those with a large VSD in terms of their development of CHF and pulmonary vascular obstructive disease.
5. The combination of VSD and PS allows considerably longer survival without surgery because the pulmonary vascular bed is protected from developing pulmonary hypertension, but this combination carries a high surgical risk for correction.
FIGURE 14-5 Diagram of the coronary artery anatomy in 32 patients with transposition of the great arteries (TGA). The orientation of the figures is that of a parasternal short-axis echocardiographic view. LAD, left anterior descending artery; LCCA, left circumflex coronary artery; RCA, right coronary artery. (From Pasquini L, Sanders SP, Parness IA, et al: Diagnosis of coronary artery anatomy by two-dimensional echocardiography in patients with transposition of the great arteries. Circulation 75:557–564, 1987.)
Management
Medical
1. The following measures should be carried out to stabilize the patient before an emergency cardiac catheterization (if performed) or a surgical procedure is carried out:
a. Arterial blood gases and pH should be obtained, and metabolic acidosis should be corrected. Hypoglycemia and hypocalcemia, if present, should be treated.
b. PGE1 infusion should be started to improve arterial oxygen saturation by reopening the ductus (see Appendix E for the dosage). This should be continued throughout the cardiac catheterization or until the time of surgery.
c. Oxygen should be administered for severe hypoxia. Oxygen may help lower pulmonary vascular resistance (PVR) and increase pulmonary blood flow (PBF), which in turn increases systemic arterial oxygen saturation.
2. Before surgery, cardiac catheterization and a balloon atrial septostomy (i.e., the Rashkind procedure) are often carried out to have some flexibility in planning surgery. If adequate interatrial communication exists and the anatomic diagnosis of TGA is clear by echocardiographic examination, the patient may go to surgery without cardiac catheterization or the balloon atrial septostomy. The need for the balloon septostomy may be determined by inadequate atrial mixing through the PFO (evidenced with a high Doppler flow velocity of >1 m/sec) or a lack of readiness for surgical intervention.
In the balloon atrial septostomy, a balloon-tipped catheter is advanced into the left atrium (LA) through the PFO. The balloon is inflated with diluted radio-opaque dye and abruptly and forcefully withdrawn to the right atrium (RA) under fluoroscopic or echocardiographic monitoring. This procedure creates a large defect in the atrial septum through which an improved intracardiac mixing occurs. An increase in the oxygen saturation of 10% or more and a minimal interatrial pressure gradient are considered satisfactory results of the procedure.
3. CHF may be treated with diuretics (and digoxin).
Surgical
Palliative Procedure
No palliative procedure is performed unless an arterial switch operation (ASO) cannot be performed early in life.
Definitive Repair
Historically, definitive surgeries performed for TGA were procedures that switched right- and left-sided blood at three levels: the atrial level (intraatrial repair surgeries such as the Senning or Mustard operation), the ventricular level (i.e., Rastelli operation), and the great artery level (ASO). At this time, ASO is clearly the procedure of choice, and intraatrial repair surgeries are very rarely performed only under unusual situations. The Damus-Kaye-Stansel operation in conjunction with the Rastelli operation can be performed in patients with VSD and subaortic stenosis. Because of a relatively poor long-term result of the Rastelli operation, other options such as the Nikaidoh operation or REV (réparation à I’étage ventriculare) procedure have become more popular recently.
Procedures
1. Atrial baffle operations (Mustard and Senning operations)
These procedures reroute pulmonary and systemic venous returns at the atrial level with resulting physiologic correction. The pulmonary venous blood eventually goes to the aorta, and the systemic venous blood goes to the PA (see Fig. 14-6 for the hemodynamic results of atrial baffle operation). The Mustard operation uses a pericardial or a prosthetic baffle, and the Senning operation uses the patient’s own atrial septal flap and the RA free wall to redirect the venous returns.
A number of long-term problems have been reported, including superior vena cava (SVC) obstruction (<5% of all cases), baffle leak (<20%), absence of sinus rhythm (>50%), frequent atrial and ventricular arrhythmias with occasional sudden death, tricuspid valve insufficiency (rare), and RV (i.e., systemic ventricular) dysfunction or failure. The ASO has largely replaced the atrial baffle operation. There are, however, rare indications for atrial baffle operations, including a situation in which relative contraindications of the ASO exist (e.g., coronary arteries that are difficult to transfer).
2. Rastelli operation. In patients with VSD and severe PS, redirection of the pulmonary and systemic venous blood is carried out at the ventricular level. The LV is directed to the aorta by creating an intraventricular tunnel between the VSD and the aortic valve. A valved conduit or a homograft is placed between the RV and the PA (Fig. 14-7). Most surgeons prefer to delay this procedure until after the first year of life. The mortality rate is between 10% and 29%.
FIGURE 14-6 Atrial baffle operation. The hemodynamic results of the Mustard and Senning operations are shown. Systemic venous blood (shaded) is redirected at the atrial level to the anatomic left atrium (LA) and left ventricle (LV) and eventually to the pulmonary circulation. Pulmonary venous blood is redirected at the atrial level to the anatomic right atrium (RA) and right ventricle (RV) through the tricuspid valve and to the aorta. AO, aorta; IVC, inferior vena cava; PA, pulmonary artery; P.V. atrium, pulmonary venous atrium; S.V. atrium, systemic venous atrium; SVC, superior vena cava.
FIGURE 14-7 The Rastelli operation. A, In patients with D-transposition of the great arteries (D-TGA), ventricular septal defect (VSD) and severe pulmonary stenosis (PS), the pulmonary artery (PA) is divided from the left ventricle (LV), and the cardiac end is oversewn (arrow). B, An intracardiac tunnel (arrow) is placed between the large VSD and the aorta (AO) so that the LV communicates with the aorta. C, The right ventricle (RV) is connected to the divided PA by a valved conduit or an aortic homograft. RA, right atrium.
Complications after the Rastelli operation include conduit obstruction (especially in those containing porcine heterograft valves) and complete heart block (which rarely occurs). The conduit needs to be replaced as the child grows. Occasionally, LVOT obstruction occurs at the level of the VSD or at the level of the intraventricular tunnels. More importantly, the long-term results are not optimal, with the 20-year survival rate at about 50%. Two alternative procedures are now available, the REV procedure and the Nikaidoh procedure (see later discussion of these procedures).
3. Arterial switch operation
The ASO is now firmly established as the procedure of choice. There are almost no situations which would justify the performance of a Senning or Mustard procedure for D-TGA. The coronary arteries are transplanted to the PA, and the proximal great arteries are connected to the distal end of the other great artery, resulting in an anatomic correction (Fig. 14-8). This procedure has advantages over the atrial baffle operations because it is an anatomic (not physiologic) correction, and long-term complications are infrequent. This procedure is indicated not only for simple TGA but also TGA with other associated anomalies (e.g., VSD or PDA) and the Taussig-Bing type of double outlet right ventricle (DORV) with subpulmonary VSD. The operative mortality rate for neonates with TGA and intact ventricular septum is down to around 6%.
FIGURE 14-8 Arterial switch operation. A, The aorta (AO; unshaded) is transected slightly above the coronary ostia, and the pulmonary artery (PA; shaded) is also transected at about the same level. The ascending aorta is lifted, and both coronary arteries are removed from the aorta with triangular buttons. B, Triangular buttons of similar size are made at the proper position in the PA trunk. C, The coronary arteries are transplanted to the PA trunk. The ascending aorta is brought behind the PA (called the Lecompte maneuver) and is connected to the proximal PA to form a neoaorta (Noe-AO). D, The triangular defects in the proximal aorta are repaired, and the proximal aorta is connected to the distal portion of the divided PA. Note that the neo-PA is in front of the neoaorta.
Complications after the ASO are infrequent. Normal sinus rhythm is usually present, arrhythmias are extremely rare, and LV function is usually normal. The following complications may occur after the ASO:
a. Coronary artery obstruction, which may lead to myocardial ischemia, infarction, and even death, is a serious but a rare complication.
b. Supravalvular PS at the anastomosis site (∼12%) is the most common cause for reoperation, although the incidence has decreased.
c. Neoaortic valvular regurgitation and supravalvular neoaortic stenosis are rare complications.
The following factors are important for a successful ASO.
1) LV pressure. An LV that can support the systemic circulation after surgery must exist. The LV pressure should be near systemic levels at the time of surgery so that the ASO should be performed shortly after birth. The time limit is 3 weeks of age (although some suggest an upper limit of 8 week of age).
2) Coronary artery anatomy. Almost all coronary artery patterns in TGA are amenable to the ASO. However, the risk is slightly higher when either one or both coronary arteries passes between the great arteries. The single coronary artery is transferable by various surgical techniques.
Currently, other associated anomalies are repaired at the time of the ASO in the neonatal period.
a. For patients with associated VSD, the VSD is repaired through the atrial approach or through the pulmonary valve. The mortality rate is around 6%.
b. For patients with PDA and VSD, the PDA is ligated, and the VSD is closed.
c. Mild pulmonary valve stenosis or dynamic subpulmonary stenosis does not preclude a successful ASO.
Two-stage switch operation. In patients whose LV pressure is low (because of missing the chance for an early ASO), it can be raised by PA banding, either with or without a shunt procedure, for 7 to 10 days (in cases of a “rapid two-stage switch operation”) or for several months before undertaking the switch operation. LV pressure greater than 85% of the RV pressure appears to be satisfactory for the switch operation. The rapid switch is preferable to a longer waiting period, which results in scarring and adhesions of the PA after PA banding. Scarring makes PA reconstruction and anastomosis of the great arteries difficult, and adhesions obscure coronary artery anatomy.
FIGURE 14-9 Réparation à I܀étage Iventriculare (REV) procedure for patients with D-transposition of the great arteries (D-TGA), ventricular septal defect (VSD), and severe pulmonary stenosis (PS). A, A schematic drawing of D-TGA with VSD and severe PS (with a relatively small pulmonary artery [PA]). The broken lines indicate the planned aortic and right ventricular (RV) incision sites. The broken circle indicates a VSD. B, The aorta and PA have been transected, and the right pulmonary artery (RPA) is brought anterior to the aorta (Lecompte maneuver). The proximal PA has been oversewn. The VSD is exposed through the right ventriculotomy. (Note that these figures have expanded ventriculotomy to allow visualization of intracardiac structures.) Dotted hemi-circular lines indicate the portion of the infundibular septum to be excised to enlarge the VSD. C, The aortic valve is well shown by retractors. The broken line indicates the planned site of a patch placement for the LV–aorta (AO) connection. The transected aorta has been reconnected behind the RPA. D, The completed LV-to-AO tunnel is shown (marked LVOT [left ventricular outflow tract] patch). The superior portion of the right ventriculotomy is sutured directly to the posterior portion of the main PA. E, A pericardial or synthetic patch is used to complete the RV-to-PA reconstruction (marked RVOT [right ventricular outflow tract] patch).
Staged conversion to ASO. Some patients who received an atrial baffle operation develop RV failure with severe tricuspid valve regurgitation. For these patients, staged conversion to ASO can be done. Initially, a PA band is placed to raise the LV pressure. This is followed by an ASO with a higher mortality rate (≈25%–33%). Alternatively, after PA band, the Damus-Kaye-Stansel operation can be performed, which does not require transfer of coronary arteries. Transfer of coronary arteries is much more difficult in these patients because of dense adhesions.
4. REV procedure. This procedure, first reported by Lecompte, may be performed for patients with D-TGA associated with VSD and severe PS, instead of the Rastelli operation. The procedure consists of (1) infundibular resection to enlarge the VSD, (2) intraventricular baffle to direct LV output to the aorta, (3) aortic transection to perform the Lecompte maneuver (by which the right pulmonary artery (RPA) is brought anterior to the ascending aorta), and (4) direct RV-to-PA reconstruction by using an anterior patch (Fig. 14-9). This may require fewer reoperations than the Rastelli procedure. Lecompte reported 50 cases (4 mo–15 yr) with an 18% operative mortality rate.
5. Nikaidoh procedure. This procedure is another surgical option for patients with D-TGA, VSD, and severe PS. In this procedure, the aortic root is mobilized and translocated to the pulmonary position. The repair consists of the following: (1) harvesting the aortic root from the RV (with attached coronary arteries in the original procedure), (2) relieving the LVOT obstruction (by enlarging the VSD by means of dividing the outlet septum and excising the pulmonary valve), (3) reconstructing the LVOT (with posteriorly translocated aortic root and the VSD patch), and (4) reconstructing the right ventricular outflow tract (RVOT) (with a pericardial patch or a homograft). In the modified Nikaidoh procedure, one or both coronary arteries are moved to a more favorable position as necessary (not shown), and the Lecompte maneuver is also performed (Fig. 14-10). The hospital mortality is less than 10%.
FIGURE 14-10 Nikaidoh procedure (for patients with D-transposition of the great arteries [D-TGA], ventricular septal defect [VSD], and severe pulmonary stenosis [PS]). A, Schematic drawing of D-TGA with VSD and severe PS (with relatively small pulmonary artery [PA]) is shown. The circular broken line around the aorta is the planned incision site for aortic root mobilization. The smaller broken circle indicates a VSD. B, The aortic root has been mobilized by a circular incision around the aortic root, which leaves an opening in the right ventricular (RV) free wall. The main PA is also transected. Through the opening, part of the VSD, the ventricular septum, and the hypoplastic PA stump are seen. The dotted vertical line in the ventricular septum (in the smaller inset in B) is the planned incision through the infundibular septum. C, In the inset, the incision in the infundibular septum has created a large opening, which includes the PA annulus and stump and the VSD. D, In the large inset, the posterior portion of the aorta is directly sutured to the PA stump, which results in a large VSD. This completes translocation of the aorta to the original PA position. The thick oval-shaped broken line that goes through the front of the transected aortic root is the planned site for placement of the left ventricular (LV) outflow tract (LVOT) patch, which will direct the LV flow to the aorta. E, The completed tunnel is shown (marked LVOT patch, which directs the LV flow to the aorta). The distal segment of the main PA is fixed to the aorta. Some surgeons use the Lecompte maneuver to bring the right pulmonary artery (RPA) in front of the ascending aorta (as shown here). F, A pericardial patch is oversewn to complete the RV-to-PA connection (marked RVOT [RV outflow tract] patch).
6. Damus-Kaye-Stansel operation. Infants with a large VSD and significant subaortic stenosis may receive the Damus-Kaye-Stansel operation at 1 to 2 years of age. In this procedure, the coronary arteries are not transferred to a neoaorta. Instead, the subaortic stenosis is bypassed by connecting the proximal PA trunk to the ascending aorta. The VSD is closed, and a conduit is placed between the RV and the distal PA (Fig. 14-11). The mortality rate is considerable, ranging from 15% to 30%.
The Damus-Kaye-Stansel operation is also applicable in patients with single ventricle and TGA with an obstructive bulboventricular foramen (BVF) or DORV with subaortic stenosis (see Fig. 14-62).
Surgical management for patients with TGA and various associated defects is summarized in Figure 14-12.
Follow-up After Arterial Switch Operation
Although the complication rate is much lower for arterial switch than for atrial baffle repair, regular follow-up is needed to detect possible complications, such as stenosis of the PA or aorta in the supravalvular regions, coronary artery obstruction with myocardial ischemia or infarction, ventricular dysfunction, arrhythmias, and semilunar valve regurgitation. These complications are, for the most part, hemodynamically insignificant or infrequent.
FIGURE 14-11 Damus-Kaye-Stansel operation for complete transposition of the great arteries (D-TGA) + ventricular septal defect (VSD + subaortic stenosis. A, D-TGA with VSD and subaortic stenosis is illustrated. The main pulmonary artery (MPA) is transected near its bifurcation. An appropriately positioned and sized incision is made in the ascending aorta (AO). B, The proximal MPA is anastomosed end to side to the ascending aorta using either a Dacron tube or Gore-Tex. This channel will direct left ventricular blood to the aorta. The aortic valve is either closed or left unclosed. The VSD is closed (through a right ventriculotomy). C, A valved conduit is placed between the right ventricle (RV) and the distal pulmonary artery (PA). This channel will carry RV blood to the PA. LV, left ventricle; RA, right atrium.
FIGURE 14-12 Surgical approaches to transposition of the great arteries with various associated defects. ASO, arterial switch operation; BT, Blalock-Taussig; PDA, patent ductus arteriosus; PS, pulmonary stenosis; REV, réparation à I܀étage ventriculare; TGA, transposition of the great arteries; VSD, ventricular septal defect.
Coronary artery obstruction after the surgery is a concern. In one study, about 5% of postoperative arterial switch patients had coronary arterial abnormalities by coronary angiography; some of them had no signs of ischemia by history, ECG, and echocardiographic studies. A periodic follow-up is recommended with ECG, echocardiography, exercise stress test (in older children), magnetic resonance imaging (MRI) or computed tomography (CT), or coronary angiography. MRI can provide a comprehensive anatomic and functional evaluation for coronary ischemia noninvasively, including myocardial perfusion and viability information.
Congenitally Corrected Transposition of the Great Arteries
Prevalence
Congenitally corrected transposition of the great arteries (or L-TGA) occurs in fewer than 1% of all patients with CHDs.
FIGURE 14-13 Diagram of congenitally corrected transposition of the great arteries (L-TGA). There is an inversion of ventricular chambers with their corresponding atrioventricular valves. The great arteries are transposed, but functional correction results, with oxygenated blood going to the aorta. Unfortunately, a high percentage of the patients with L-TGA have associated defects, some of which may cause cyanosis. AO, aorta; LA, left atrium; LV, left ventricle; PA, pulmonary artery; RA, right atrium; RV, right ventricle.
Pathology
1. In this condition, the visceroatrial relationship is normal, but there is ventricular inversion. The RA is to the right of the LA and receives systemic venous blood. The RA empties into the anatomic LV through the mitral valve, and the LA empties into the RV through the tricuspid valve. For this to occur, the RV is located to the left of the LV (or the LV is located to the right of the RV), which is called ventricular inversion(Fig. 14-13). The great arteries are transposed, with the aorta rising from the RV and the PA rising from the LV. The aorta is located anterior to and left of the PA; thus, the prefix of L is used, and the condition is called L-TGA (see Fig. 17-4, D). The result is functional correction in that oxygenated blood coming into the LA goes to the anatomic RV and then flows out to the aorta. This is why the term corrected is used to describe this condition.
2. Theoretically, no functional abnormalities exist, but unfortunately, most cases are complicated by associated intracardiac defects, AV conduction disturbances, and arrhythmias.
a. VSD occurs in 80% of all cases.
b. PS, both valvular and subvalvular, occurs in 50% of patients and is usually associated with VSD.
c. Systemic AV valve (tricuspid valve) regurgitation occurs in 30% of patients.
d. Occasionally, complex associated defects are present with hypoplastic ventricle, AV valve abnormalities, or multiple VSDs.
e. Both varying and progressive degrees of AV block and paroxysmal supraventricular tachycardia (SVT) frequently occur.
3. The cardiac apex is in the right chest (dextrocardia) in about 50% of cases.
4. The coronary arteries show a mirror-image distribution. The right coronary artery supplies the anterior descending branch and gives rise to a circumflex; the left coronary artery resembles a right coronary artery.
Clinical Manifestations
History
1. Patients are asymptomatic when L-TGA is not associated with other defects.
2. During the first months of life, most patients with associated defects become symptomatic with cyanosis resulting from VSD and PS or CHF resulting from a large VSD.
3. Exertional dyspnea and easy fatigability may develop with regurgitation of the systemic AV valve (i.e., anatomic tricuspid valve).
Physical Examination
1. The patient is cyanotic if PS and VSD are present.
FIGURE 14-14 Tracing from an 8-year-old girl with congenitally corrected transposition of the great arteries, ventricular septal defect, and pulmonary stenosis. Note that no Q waves are seen in leads V5 and V6. Instead, the Q waves are seen in V4R and V1. This suggests ventricular inversion. The electrocardiogram also suggests hypertrophy of the right-sided ventricle (anatomic left ventricle).
2. Hyperactive precordium occurs in the presence of a large VSD. Systolic thrill occurs in the presence of PS with or without VSD.
3. The S2 is loud and single at the upper left or right sternal border. A grade 2 to 4 of 6 harsh, holosystolic murmur along the lower left sternal border indicates the presence of VSD or systemic AV valve regurgitation. A grade 2 to 3 of 6 ejection systolic murmur is present at the upper left or right sternal border if PS is present. An apical diastolic rumble may be audible if a large VSD or significant tricuspid regurgitation (TR) is present.
4. Bradycardia, tachycardia, or irregular rhythm requires an investigation for AV conduction disturbances or arrhythmias.
Electrocardiography
1. The absence of Q waves in V5 and V6 or the presence of Q waves in V4R or V1 is characteristic of the condition (Fig. 14-14). This is because the direction of ventricular septal depolarization is from the embryonic LV to RV.
2. Varying degrees of AV block are common. First-degree AV block is present in about 50% of patients. Second-degree AV block may progress to complete heart block.
3. Atrial arrhythmias and Wolff-Parkinson-White (WPW) preexcitation are occasionally present.
4. Atrial or ventricular hypertrophy (or both) may be present in complicated cases.
Radiography
1. A straight, left upper cardiac border, formed by the ascending aorta, is a characteristic finding (Fig. 14-15).
2. Cardiomegaly and increased pulmonary vascular markings are present when the condition is associated with VSD.
3. Pulmonary venous congestion and LA enlargement may be seen with severe left-sided AV valve regurgitation.
4. Positional abnormalities (e.g., dextrocardia, mesocardia) may be present.
Echocardiography
With use of the segmental approach (see Chapter 17), the diagnosis of L-TGA can be made easily, and associated anomalies can be detected and quantitated.
1. The parasternal long-axis view is obtained from a more vertical and leftward scan than with a normal heart. The aorta, which arises from the posterior ventricle, is not in fibrous continuity with the AV valve.
2. In the parasternal short-axis scan, a “double circle” of the semilunar valves is imaged instead of the normal “circle and sausage” pattern. The posterior circle is the PA without demonstrable coronary arteries. The aorta is usually anterior to and left of the PA. The LV, which has two well-defined papillary muscles, is seen anteriorly and on the right and is connected to the characteristic “fish mouth” appearance of the mitral valve.
FIGURE 14-15 Posteroanterior view of an actual chest roentgenogram (A) and a diagrammatic representation (B) from a 10-year-old child with congenitally corrected transposition of the great arteries. Note the straight left cardiac border formed by the ascending aorta. Ao, aorta; LV, left ventricle; PA, pulmonary artery; RA, right atrium; RV, right ventricle.
3. In the apical and subcostal four-chamber views, the LA is connected to the tricuspid valve (which has a more apical attachment to the ventricular septum than the other) and the RA is connected to the mitral valve. The anterior artery (aorta) arises from the left-sided morphologic RV, and the posterior artery with bifurcation (PA) arises from the right-sided morphologic LV.
4. The situs solitus of the atria is confirmed by the drainage of systemic veins (i.e., inferior vena cava [IVC] and SVC) to the right-sided atrium and the drainage of pulmonary veins to the left-sided atrium.
5. The following associated abnormalities should be looked for, and their functional significance should be assessed by the Doppler and color-flow studies: type and severity of PS, size and location of VSD, straddling of the AV valve, and so on.
Other Studies
Occasionally, angiography may be necessary to image coronary artery anatomy, although CT or MRI may provide this information noninvasively.
Natural History
The clinical course is determined by the presence or absence of associated defects and complications.
1. Some palliative surgeries are usually needed in infancy when L-TGA is associated with other defects (e.g., PA banding for a large VSD or a systemic-to-PA shunt for severe PS). Without these procedures, 20% to 30% of patients die in the first year. CHF is the most common cause of death.
2. Regurgitation of the systemic AV valve (anatomic tricuspid valve) develops in about 30% of patients. This is often associated with dysplastic or Ebstein-like tricuspid valves.
3. Progressive AV conduction disturbances may occur, including complete heart block in up to 30% of cases. These disturbances occur more often in patients without VSD than in those with VSD. Sudden death rarely occurs.
4. Occasional adult patients without major associated defects are asymptomatic.
Management
Medical
1. Treatment with anticongestive agents is necessary if CHF develops.
2. Antiarrhythmic agents are used for arrhythmias.
FIGURE 14-16 Surgical summary of congenitally corrected transposition of the great arteries (L-TGA). AO, aorta; ASO, arterial switch operation; PA, pulmonary artery; RV, right ventricle; PS, pulmonary stenosis (= LV outflow tract obstruction); TGA, transposition of the great arteries; TR, tricuspid regurgitation (= left-sided AV valve regurgitation); VSD, ventricular septal defect.
Surgical
Palliative Procedures
1. A modified Blalock-Taussig (BT) shunt is necessary for patients with severe PS (usually associated with VSD).
2. PA banding may be needed for uncontrollable CHF in early infancy.
Definitive Procedures
There are two major approaches to surgical management of L-TGA, classic repair and anatomic repair. Patients with regurgitation of the tricuspid valve (systemic AV valve) or RV dysfunction need the anatomic repair in which the LV is made the systemic ventricle. The surgical approach for L-TGA is summarized in Figure 14-16.
1. Classic repair leaves the anatomic RV as the systemic ventricle. A competent tricuspid valve (or left AV valve) and good RV function are required. Even after repair, progressive TR and RV failure may develop.
a. In patients with VSD, the VSD is closed through an atrial approach. Complete heart block is a complication of the surgery, occurring 15% to 30% of the time. The mortality rate is 5% to 10%, which is higher than that for a simple VSD.
b. In patients with VSD and PS (or LVOT obstruction), the VSD is closed and an LV-to-PA conduit is placed. The surgical mortality rate is higher (10%–15%).
2. Anatomic repair makes the anatomic LV the systemic ventricle, which may reduce the likelihood of TR and RV failure. This repair is technically more difficult than the classic repair and carries a higher risk, but this procedure is a better choice for patients with TR or RV dysfunction.
a. A combination of Senning procedure (which is an atrial switch operation; see Fig. 14-6) and ASO (see Fig. 14-8), called a “double switch” operation, is performed in patients with VSD. A PA banding is initially placed to delay the procedure until after 1 year of age. Closure of VSD, if present, is performed through the RA. The hospital mortality rate for the “double switch” operation is approximately 10%, with complete heart block occurring 0% to 23% of the time.
b. In patients with VSD and PS (or LVOT obstruction), a combination of the Senning operation and Rastelli operation is performed. VSD is closed through a right ventriculotomy in such a way to connect the VSD to the aorta. Enlargement of the VSD is often necessary. RV-to-PA continuity is established with an extracardiac valved conduit. The hospital mortality rate is around 10%. TR improves after the procedure.
3. Fontan-type operation. In patients with complex intracardiac anatomies, including hypoplasia of one ventricle, straddling AV valves, or multiple VSDs, bidirectional Glenn operation or a full Fontan procedure is indicated.
4. Other procedures
a. Valve replacement. For patients with significant TR, valve replacement is required in about 15%, including those without other associated defects.
b. Pacemaker implantation is required for either spontaneous or postoperative complete heart block.
c. Cardiac transplantation. Some patients with complex L-TGA eventually become candidates for cardiac transplantation.
Postoperative Follow-up
1. Follow-up every 6 to 12 months is required for a possible progression of AV conduction disturbances, arrhythmias, or worsening of anatomic tricuspid valve regurgitation.
2. Routine pacemaker care, if a pacemaker is implanted, should be conducted.
3. Activity restriction is indicated if significant hemodynamic abnormalities persist.
Tetralogy of Fallot
Prevalence
Tetralogy of Fallot occurs in 5% to 10% of all CHDs. This is probably the most common cyanotic heart defect.
Pathology
1. The original description of TOF included the following four abnormalities: a large VSD, RVOT obstruction, RVH, and overriding of the aorta. In actuality, only two abnormalities are required, a VSD large enough to equalize pressures in both ventricles and an RVOT obstruction. The RVH is secondary to the RVOT obstruction, and the overriding of the aorta varies (Fig. 14-17).
2. The VSD in TOF is a large perimembranous defect with extension into the subpulmonary region.
3. The RVOT obstruction is most frequently in the form of infundibular stenosis (45%). The obstruction is rarely at the pulmonary valve level (10%). A combination of the two may also occur (30%). The pulmonary valve is atretic in the most severe form of the anomaly (15%), which is discussed under a separate heading in this chapter.
4. The pulmonary annulus and main PA are variably hypoplastic in most patients. The PA branches are usually small, although marked hypoplasia is uncommon. Stenosis at the origin of the branch PAs, especially the left PA, is common. Occasionally, systemic collateral arteries feed into the lungs, especially in severe cases of TOF.
5. Right aortic arch is present in 25% of cases, with some of them having symptoms of vascular ring.
6. In about 5% of TOF patients, abnormal coronary arteries are present. The most common abnormality is the anterior descending branch arising from the right coronary artery and passing over the RVOT, which prohibits a surgical incision in the region.
7. Complete AV canal defect occurs in approximately 2% of patients with TOF, more commonly among patients with Down syndrome, called “canal tet.” In these patients, the VSD has a large outlet component in addition to the inlet portion associated with the AV canal.
FIGURE 14-17 Pathologic anatomy of tetralogy of Fallot viewed with the right ventricular (RV) free wall removed. A large ventricular septal defect (VSD) is present underneath the aortic valve. Hypertrophied parietal and septal bands produce infundibular stenosis (marked x). A stenotic and hypoplastic main pulmonary artery (PA) is shown. The RV muscle is hypertrophied. TV, tricuspid valve. (Hirsch JC, Bove EL. Tetralogy of Fallot. In Mavroudis C. Pediatric Cardiac Surgery, 3rd ed. Philadelphia, Mosby, 2003. Reproduced with permission).
FIGURE 14-18 Cardiac findings in cyanotic tetralogy of Fallot. A long ejection systolic murmur at the upper and mid left sternal border and a loud, single S2 are characteristic auscultatory findings of TOF. EC, ejection click.
Clinical Manifestations
History
1. A heart murmur is audible at birth.
2. Most patients are symptomatic with cyanosis at birth or shortly thereafter. Dyspnea on exertion, squatting, or hypoxic spells develop later even in mildly cyanotic infants (see Chapter 11).
3. Occasional infants with acyanotic TOF may be asymptomatic or may show signs of CHF from a large left-to-right ventricular shunt.
Physical Examination (Fig. 14-18)
1. Varying degrees of cyanosis, tachypnea, and clubbing (in older infants and children) are present.
2. An RV tap along the left sternal border and a systolic thrill at the upper and mid-left sternal borders are commonly present (50%).
3. An ejection click that originates in the aorta may be audible. The S2 is usually single because the pulmonary component is too soft to be heard. A long, loud (grade 3 to 5 of 6) ejection-type systolic murmur is heard at the mid-and upper left sternal borders. This murmur originates from the PS but may be easily confused with the holosystolic regurgitant murmur of a VSD. The more severe the obstruction of the RVOT, the shorter and softer the systolic murmur.
4. In the acyanotic form, a long systolic murmur, resulting from VSD and infundibular stenosis, is audible along the entire left sternal border, and cyanosis is absent. Thus, auscultatory findings resemble those of a small-shunt VSD (but, unlike VSD, the ECG shows RVH or BVH).
Electrocardiography
1. Right-axis deviation (RAD) (+120 to +150 degrees) is present in cyanotic TOF. In the acyanotic form, the QRS axis is normal.
2. RVH is usually present, but the strain pattern is unusual (because RV pressure is not suprasystemic). BVH may be seen in the acyanotic form. RAH is occasionally present.
Radiography
Cyanotic Tetralogy of Fallot
1. The heart size is normal or smaller than normal, and pulmonary vascular markings are decreased. “Black” lung fields are seen in TOF with pulmonary atresia.
2. A concave main PA segment with an upturned apex (i.e., “boot-shaped” heart or coeur en sabot) is characteristic (Fig. 14-19).
3. RA enlargement (25%) and right aortic arch (25%) may be present.
Acyanotic Tetralogy of Fallot
Radiographic findings of acyanotic TOF are indistinguishable from those of a small to moderate VSD (but patients with TOF have RVH rather than LVH on the ECG).
Echocardiography
Two-dimensional echocardiography and Doppler studies usually make the diagnosis and quantitate the severity of TOF.
1. A large, perimembranous infundibular VSD and overriding of the aorta are readily imaged in the parasternal long-axis view (Fig. 14-20).
2. Anatomy of the RVOT, the pulmonary valve, the pulmonary annulus, and the main PA and its branches is imaged in the parasternal short-axis and subcostal short-axis views. These views allow systematic evaluation of the severity of obstruction at different levels.
3. Doppler studies estimate the pressure gradient across the RVOT obstruction.
FIGURE 14-19 Posteroanterior view of chest roentgenogram in tetralogy of Fallot. The heart size is normal, and pulmonary vascular markings are decreased. A hypoplastic main pulmonary artery segment contributes to the formation of the “boot-shaped” heart.
4. Anomalous coronary artery distribution can be imaged accurately by echocardiographic studies (Fig. 14-21). The major concern is to rule out any branch of the coronary artery crossing the RVOT. Thus, preoperative cardiac catheterization solely for the diagnosis of coronary artery anatomy is not necessary.
5. Associated anomalies such as ASD and persistence of the left superior vena cava (LSVC) can be imaged.
Other Studies
Two-dimensional echocardiographic and Doppler studies are the primary methods of evaluation before surgery. Cardiac catheterization is reserved only for patients with specific unanswered questions after echocardiographic study.
FIGURE 14-20 Parasternal long-axis view in a patient with tetralogy of Fallot. Note a large subaortic ventricular septal defect (arrow) and a relatively large aorta (AO) overriding the interventricular septum (IVS). AV, aortic valve; LA, left atrium; LV, left ventricle; MV, mitral valve; RV, right ventricle.
FIGURE 14-21 Patterns of coronary artery anatomy in tetralogy of Fallot (TOF) as imaged from the parasternal short-axis view. The percentage of each pattern seen in 598 patients with TOF is indicated in the lower left corner of each box. Ant, anterior; CX, left circumflex branch; L, left; LAD, left anterior descending coronary artery; R, right; RCA, right coronary artery; Post, posterior. (From Need LR, Powell AJ, del Nide P, Geva T: Coronary echocardiography in tetralogy of Fallot: Diagnostic accuracy, resource utilization and surgical implications over 13 years. J Am Coll Cardiol 36:1371–1377, 2000.)
Natural History
1. Infants with acyanotic TOF gradually become cyanotic. Patients who are already cyanotic become more cyanotic as the infundibular stenosis worsens and polycythemia develops.
2. Polycythemia develops secondary to cyanosis.∗
3. Physicians need to watch for the development of relative iron-deficiency states (i.e., hypochromia) (see Chapter 11).∗
4. Hypoxic spells may develop in infants (see Chapter 11).
5. Growth retardation may be present if cyanosis is severe.∗
6. Brain abscess and cerebrovascular accident rarely occur (see Chapter 11).∗
7. Subacute bacterial endocarditis (SBE) is occasionally a complication.∗
8. Some patients, particularly those with severe TOF, develop aortic regurgitation (AR).
9. Coagulopathy is a late complication of a long-standing cyanosis.∗
Hypoxic Spell
Hypoxic spells (also called cyanotic spells, hypercyanotic spells, “tet” spells) of TOF are not as common as they used to be because many of the patients with TOF receive surgery before they develop the spells. However, it is very important for physicians to be able to immediately recognize and treat the spells appropriately because they can lead to serious complications of the CNS.
Hypoxic spells are characterized by a paroxysm of hyperpnea (i.e., rapid and deep respiration), irritability and prolonged crying, increasing cyanosis, and decreasing intensity of the heart murmur. Hypoxic spells occur in infants, with a peak incidence between 2 and 4 months of age. These spells usually occur in the morning after crying, feeding, or defecation. A severe spell may lead to limpness, convulsion, cerebrovascular accident, or even death. There appears to be no relationship between the degree of cyanosis at rest and the likelihood of having hypoxic spells (see Chapter 11).
Treatment of the hypoxic spell strives to break the vicious circle of the spell (see Fig. 11-11). Physicians may use one or more of the following to treat the spell.
1. The infant should be picked up and held in a knee–chest position.
2. Morphine sulfate, 0.2 mg/kg administered subcutaneously or intramuscularly, suppresses the respiratory center and abolishes hyperpnea (and thus breaks the vicious cycle).
3. Oxygen is usually administered, but it has little demonstrable effect on arterial oxygen saturation.
4. Acidosis should be treated with sodium bicarbonate (NaHCO3), 1 mEq/kg administered IV. The same dose can be repeated in 10 to 15 minutes. NaHCO3 reduces the respiratory center–stimulating effect of acidosis.
With the preceding treatment, the infant usually becomes less cyanotic, and the heart murmur becomes louder, which indicates an increased amount of blood flowing through the stenotic RVOT. If the hypoxic spells do not fully respond to these measures, the following medications can be tried:
1. Ketamine, 1 to 3 mg/kg (average, 2 mg/kg) administered IV over 60 seconds, works well. It increases the systemic vascular resistance (SVR) and sedates the infant.
2. Propranolol, 0.01 to 0.25 mg/kg (average, 0.05 mg/kg) administered by slow IV push, reduces the heart rate and may reverse the spell.
Management
Medical
1. Physicians should recognize and treat hypoxic spells (see the preceding section and Chapter 11). It is important to educate parents to recognize the spells and know what to do.
2. Oral propranolol therapy, 0.5 to 1.5 mg/kg every 6 hours, is occasionally used to prevent hypoxic spells while waiting for an optimal time for corrective surgery in the regions where open heart surgical procedures are not well established for small infants.
3. Balloon dilatation of the RVOT and pulmonary valve, although not widely practiced, has been attempted to delay repair for several months.
4. Relative iron-deficiency states should be detected and treated. Iron-deficient children are more susceptible to cerebrovascular complications. Normal hemoglobin or hematocrit values or decreased red blood cell indices indicate an iron-deficiency state in cyanotic patients.
Surgical
Palliative Shunt Procedures
Indications
Shunt procedures are performed to increase PBF (Fig. 14-22). Indications for shunt procedures vary from institution to institution. Many institutions, however, prefer primary repair without a shunt operation regardless of the patient’s age. However, when the following situations are present, a shunt operation may be chosen rather than primary repair.
1. Neonates with TOF and pulmonary atresia
2. Infants with hypoplastic pulmonary annulus, which requires a transannular patch for complete repair
3. Children with hypoplastic PAs
4. Unfavorable coronary artery anatomy
5. Infants younger than 3 to 4 months old who have medically unmanageable hypoxic spells
6. Infants weighing less than 2.5 kg
Procedures, Complications, and Mortality
Although several other procedures were performed in the past (see Fig. 14-22), a modified BT (Gore-Tex interposition) shunt is the only procedure performed at this time.
1. Classic BT shunt, anastomosed between the subclavian artery and the ipsilateral PA, is usually performed for infants older than 3 months because the shunt is often thrombosed in young infants. A right-sided shunt is performed in patients with left aortic arch; a left-sided shunt is performed for right aortic arch.
2. With a modified BT shunt, a Gore-Tex interposition shunt is placed between the subclavian artery and the ipsilateral PA. This is the most popular procedure for any age, especially for infants younger than 3 months of age. Whereas a left-sided shunt is preferred for patients with left aortic arch, a right-sided shunt is preferred for patients with a right aortic arch. The surgical mortality rate is 1% or less.
3. The Waterston shunt, anastomosed between the ascending aorta and the right PA, is no longer performed because of a high incidence of surgical complications. Complications resulting from this procedure included too large a shunt leading to CHF or pulmonary hypertension and narrowing and kinking of the right PA at the site of the anastomosis. This created difficult problems in closing the shunt and reconstructing the right PA at the time of corrective surgery.
FIGURE 14-22 Palliative procedures that can be performed in patients with cyanotic cardiac defect with decreased pulmonary blood flow. The Gore-Tex interposition shunt (or modified Blalock-Taussig shunt) is the most popular systemic–to–pulmonary artery (PA) shunt procedure. AO, aorta; LV, left ventricle; RA, right atrium; RV, right ventricle.
FIGURE 14-23 Total correction of tetralogy of Fallot (TOF). A, Anatomy of TOF showing a large ventricular septal defect (VSD) and infundibular stenosis seen through a right ventriculotomy. Note that the size of the ventriculotomy has been expanded to show the VSD. B,Patch closure of the VSD and resection of the infundibular stenosis. C, Placement of a fabric patch on the outflow tract of the right ventricle (RV). AO, aorta; PA, pulmonary artery; RA, right atrium.
4. The Potts operation, anastomosed between the descending aorta and the left PA, is no longer performed either. It may result in heart failure or pulmonary hypertension, as in the Waterston operation. A separate incision (i.e., left thoracotomy) is required to close the shunt during corrective surgery, which is performed through a midsternal incision.
Complete Repair Surgery
Timing of this operation varies from institution to institution, but early surgery is generally preferred.
Indications and Timing
1. Oxygen saturation less than 75% to 80% is an indication of surgery by most centers. The occurrence of hypoxic spells is generally considered an indication for operation.
2. Symptomatic infants who have favorable anatomy of the RVOT and PAs may have primary repair at any time after 3 to 4 months of age, with some centers performing it even before 3 months of age. Most centers prefer primary elective repair by 1 to 2 years of age even if they are asymptomatic, acyanotic (i.e., “pink tet”), or minimally cyanotic.
Advantages cited for early primary repair include diminution of hypertrophy and fibrosis of the RV, normal growth of the PAs and alveolar units, and reduced incidence of postoperative ventricular arrhythmias, and sudden death.
3. Mildly cyanotic infants who have had previous shunt surgery may have total repair 1 to 2 years after the shunt operation.
4. Asymptomatic children with coronary artery anomalies may have the repair after 1 year of age, because a conduit placement may be required between the RV and the PA.
Procedure
Total repair of the defect is carried out under cardiopulmonary bypass, circulatory arrest, and hypothermia. The procedure includes patch closure of the VSD, preferably through transatrial and transpulmonary artery approach (rather than right ventriculotomy, which is shown in Fig. 14-23); widening of the RVOT by division or resection of the infundibular tissue; and pulmonary valvotomy, avoiding placement of a fabric patch whenever possible (see Fig. 14-23). Widening of the RVOT without placement of patch is more likely to be accomplished if the repair is done in early infancy. However, if the pulmonary annulus and main PA are hypoplastic, transannular patch placement is unavoidable. Whereas some centers advocate placement of a monocusp valve at the time of initial repair, others advocate pulmonary valve replacement at a later time if indicated.
The surgical approach in patients with TOF is summarized in Figure 14-24.
Mortality
For patients with uncomplicated TOF, the mortality rate is 2% to 3% during the first 2 years. Patients at risk are those younger than 3 months and older than 4 years, as well as those with severe hypoplasia of the pulmonary annulus and trunk. Other risk factors may include multiple VSDs, large aortopulmonary collateral arteries, and Down syndrome.
FIGURE 14-24 Surgery approaches for tetralogy of Fallot (TOF). BT, Blalock-Taussig; RVOT, right ventricular outflow tract; RV-PA, right ventricle–to–pulmonary artery; VSD, ventricular septal defect.
Complications
1. Bleeding problems may occur during the postoperative period, especially in older polycythemic patients.
2. Pulmonary valve regurgitation may occur, but mild regurgitation is well tolerated.
3. Right bundle branch block (RBBB) on the ECG caused by right ventriculotomy, which occurs in more than 90% of patients, is well tolerated.
4. Complete heart block (i.e., <1%) and ventricular arrhythmia are both rare.
Anomalous coronary artery
Anomalous anterior descending coronary artery arising from the right coronary artery is considered a contraindication to a primary repair because it may require placement of a conduit between the RV and PA, which is usually performed after 1 year of age. However, it is often possible to enlarge the outflow tract through a transatrial approach and by placing a short outflow patch either above or below the anomalous coronary artery. Alternatively, when a small conduit is necessary between the RV and the PA, the native outflow tract should be made as large as possible through an atrial approach, so that a “double outlet” (the native outlet and the conduit) results from the RV.
Postoperative Follow-up
1. Long-term follow-up with office examinations every 6 to 12 months is recommended, especially for patients with residual VSD shunt, residual obstruction of the RVOT, residual PA obstruction, arrhythmias, or conduction disturbances.
2. Significant pulmonary regurgitation (PR) may develop after repair of TOF. Although the PR is well tolerated for a decade or two, moderate to severe PR may eventually develop with significant RV dilatation and dysfunction, requiring surgical insertion of a homograft pulmonary valve. Severe PR left untreated may result in irreversible anatomic and functional changes in the RV, but the ideal timing of the valve replacement has been controversial. RV function is best investigated by MRI; if MRI is contraindicated because of the presence of metallic objects or cardiac pacemaker, CT should be used. The following are suggested criteria for surgical pulmonary valve replacement.
a. Recommended criteria by Geva T (2006) is primarily based on RV regurgitant fraction:
1) RV regurgitation fraction ≥25% PLUS
2) Two or more of the following criteria
a) RV end-diastolic volume index ≥160 mL/m2 (normal, <108 mL/m2)
b) RV end-systolic volume index ≥70 mL/m2 (normal, <47 mL/m2)
c) LV end-diastolic volume index ≥65 mL/m2
d) RV ejection fraction ≤45%
e) RV outflow tract aneurysm
f) Clinical criteria: exercise intolerance, syncope, presence of heart failure, sustained ventricular tachycardia, or QRS duration ≥180 msec (two last ones are known risk factors for sudden death)
3) The following are modifiers to the above criteria.
a) Presence of moderate to severe TR, residual ASD or VSD, and severe AR may trigger valve replacement.
b) If the PR is associated with the stenosis of the main or branch pulmonary arteries (natural or secondary to shunt operations), the PA stenosis should be relieved first by a balloon and/or stent procedure, which may improve PR.
c) In patients who underwent TOF repair at age 3 years or older, the valve replacement may be indicated in the presence of less severe RV dilatation and dysfunction than those 6 listed above. [Old age at surgery is an independent risk factor for impaired clinical status.]
b. Recently, Lee C. et al (2012) have recommended the following cutoff values for optimal outcome. They found the systolic volume index to be more important than the diastolic volume index in determining the outcome of surgery.
1) RV end-systolic volume index ≥80 mL/m2 and
2) RV end-diastolic volume index ≥163 mL/m2.
3. Some patients, particularly those who had Rastelli operation using valved conduit, develop valvular stenosis or regurgitation. Valvular stenosis may improve after balloon dilatation, but PR may worsen. A nonsurgical percutaneous pulmonary valve implantation technique developed by Bonhoeffer et al (2000) has been used successfully. It is marketed as the Melody transcatheter pulmonary valve (Medtronic, Minneapolis, MN) (see further discussion under TOF with pulmonary atresia in this chapter).
4. Some children develop late arrhythmias, particularly ventricular tachycardia, which may result in sudden death. Arrhythmias are primarily related to persistent RVH as a result of unsatisfactory repair.
5. Pacemaker therapy is indicated for surgically induced complete heart block or sinus node dysfunction.
6. Varying levels of activity limitation may be necessary.
7. For patients who have residual defects or have prosthetic material for repair, SBE prophylaxis should be observed throughout life.
Tetralogy of Fallot with Pulmonary Atresia (Pulmonary Atresia and Ventricular Septal Defect)
Prevalence
Pulmonary atresia occurs in about 15% to 20% of patients with TOF.
Pathology
1. The intracardiac pathology resembles that of TOF in all respects except for the presence of pulmonary atresia, the extreme form of RVOT obstruction. The atresia may be at the infundibular or valvular level.
2. The PBF is most commonly mediated through a PDA (70%) and less commonly through multiple systemic collaterals (30%), which are referred to as multiple aortopulmonary collateral arteries (MAPCAs). Both PDA and collateral arteries may coexist as the source of PBF.
3. The central PAs are usually confluent in patients with PDA (70%). In patients with MAPCAs, the central PA is frequently nonconfluent, with the right upper lobe frequently supplied by a collateral from the subclavian artery and the left lower lobe by a collateral from the descending aorta. The subgroup of the patients with MAPCAs is designated as pulmonary atresia and ventricular septal defect (PA-VSD).
4. PA anomalies are common in the form of hypoplasia, nonconfluence, and abnormal distribution.
a. The central PAs are confluent in 85% of patients; they are nonconfluent in 15%.
b. The central and branch PAs are hypoplastic in most patients, but this occurs more frequently in patients with MAPCAs than in those with PDA. The degree of PA hypoplasia is importantly related to the success of surgery (see below for further discussion of PA hypoplasia.
c. Incomplete arborization (distribution) of one or both PAs is found in 50% of patients with confluent PAs and in 80% of patients with nonconfluent PAs.
5. Collateral arteries arise most commonly from the descending aorta (occurring in two thirds of patients), less commonly from the subclavian arteries, and rarely from the abdominal aorta or its branches.
6. The ductus is small and long and arises from the transverse aortic arch and courses downward (“vertical” ductus) (Fig. 14-25).
7. The McGoon ratio and the Nakata index are used to quantitate the degree of PA hypoplasia. Small values of these measurements may adversely affect the outcome of surgeries in patients with small pulmonary arteries.
a. The McGoon ratio is the ratio of the sum of the diameter of the immediately prebranching portion of the RPA plus left pulmonary artery (LPA) divided by the diameter of the descending aorta just above the diaphragm. Normal values of the McGoon ratio are 2.0 to 2.5. Most survivors of TOF with pulmonary atresia have a ratio greater than 1. Good Fontan candidates should have a ratio greater than 1.8.
b. The Nakata index is the cross-sectional area of the RPA and LPA (in mm2) divided by the body surface area (BSA). The average diameter of both RPA and LPA are measured at the points immediately proximal to the origin of the first lobar branches at maximal and minimal during one cardiac cycle in the anteroposterior view of the pulmonary arteriogram. The cross-sectional area is calculated by using the formula, π × r2× magnification coefficient (where r is the radius or 1/2 of the measured PA diameters). A normal Nakata index is 330 ± 30 mm2/BSA. Patients with TOF with PS should have an index greater than 100 for survival. A good Fontan candidate should have an index greater than 250, and a good Rastelli candidate should have an index greater than 200. (Those with an index less than 200 should have a shunt operation rather than the Rastelli.)
Clinical Manifestations
1. These patients are cyanotic at birth. The degree of cyanosis depends on whether the ductus is patent and how extensive the systemic collateral arteries are.
2. Usually a heart murmur cannot be heard. However, a faint, continuous murmur may be audible from the PDA or collaterals. The S2 is loud and single. A systolic click is occasionally present.
3. The ECG shows RAD and RVH.
4. Chest radiography shows a normal heart size. The heart often appears as a boot-shaped silhouette (see Fig. 14-19), and the pulmonary vascularity is usually markedly decreased (i.e., “black” lung field). Rarely, children with MAPCAs have excessive PBF, and CHF may develop.
5. Echocardiographic studies show all the anatomic findings of TOF plus the absence of a direct connection between the RV and the PA. In this case, a careful examination of the central PA is necessary with measurements of the size of central and branch PAs. The small branch PAs and “vertical ductus” (see Fig. 14-25) are well imaged from a high parasternal or suprasternal transducer position. Some of the multiple collateral arteries are also imaged by echocardiography and Doppler.
FIGURE 14-25 Anatomy of the ductus arteriosus in pulmonary atresia. The size and direction of the ductus arteriosus are different between a normal fetus and a fetus with pulmonary atresia. A, In a normal fetus, the ductus is large and joins the aorta (AO) at an obtuse angle. The aortic isthmus (the portion of the aorta between the left subclavian artery and the ductus) is narrower than the descending aorta. B, In pulmonary atresia, the ductus is small because flow to the descending aorta does not go through the ductus. Furthermore, because flow is from the aorta to the pulmonary artery, the connection of the ductus with the aorta has an acute inferior angle (sometimes called “vertical” ductus). The aortic isthmus has the same diameter as the descending aorta. This type of ductus arteriosus is also found in some patients with tricuspid atresia. LPA, left pulmonary artery; MPA, main pulmonary artery; RPA, right pulmonary artery.
6. Cardiac catheterization and angiograms are sometimes needed for a complete delineation of the collaterals. Alternatively, MRI, rather than CT, is chosen for complete anatomic delineation of the aortic collaterals and PA branches.
Natural History
1. Without immediate attention to the establishment of PBF during the newborn period, most neonates who have this condition die during the first 2 years of life; however, infants with extensive collaterals may survive for a long time, perhaps for more than 15 years.
2. Occasionally, patients with excessive collateral circulation develop hemoptysis during late childhood.
Management
Medical
1. PGE1 infusion should be started as soon as the diagnosis is made or suspected to keep the ductus open for additional studies and to prepare for surgery. The starting dose of alprostadil (Prostin VR Pediatric) solution is 0.05 to 0.1 μg/kg per minute. When the desired effect is obtained, the dosage should be gradually reduced to 0.01 μg/kg per minute.
2. Emergency cardiac catheterization or MRI study is usually needed to delineate the anatomy of the PAs and systemic arterial collaterals.
Surgical
A connection must be established between the RV and true PA as early in life as possible. This may allow tiny central PAs to enlarge rapidly during the first year of life with improved arborization (distribution) of the pulmonary arteries with concurrent development of alveolar units. To achieve this goal, some centers initially use a central shunt procedure, and others proceed with an RV–PA connection.
1. Central shunt operation. Some centers use a central shunt directly connecting the ascending aorta and the hypoplastic main PA to achieve growth of the peripheral PAs (Mee procedure) (Fig. 14-26). A classic or modified BT shunt is avoided because it is difficult to perform on tiny PAs and may cause stenosis or distortion. This is then followed by unifocalization (see below for explanation), RV-PA connection, and closure of VSD. Other centers skip the shunt procedure and proceed with the connection of the RV and the main PA (see below).
2. RV-to-PA connection
a. Single-stage repair. Complete, primary surgical repair in patients with TOF and pulmonary atresia is possible only when (1) the true PAs provide most or all PBF (with O2 saturation of >75%) or (2) the central PA connects without obstruction to sufficient regions of the lungs (i.e., at least equal to one whole lung). If additional major collaterals are identified, test the level of arterial O2 saturation after occlusion of the collateral in the catheterization laboratory. If the O2 saturation remains greater than 70% to 75%, coil occlusion of the collaterals is then carried out.
FIGURE 14-26 Central end-to-side shunt (Mee procedure). A, Diagram of tetralogy of Fallot with pulmonary atresia. B, The hypoplastic pulmonary artery (PA) is anastomosed to the ascending aorta (AO) as posteriorly as possible. LV, left ventricle; RA, right atrium; RV, right ventricle; SVC, superior vena cava. (From Watterson KG, Wilkinson JL, Karly TR, Mee RBB: Very small pulmonary arteries: Central end-to-side shunt. Ann Thorac Surg 52:1131–1137, 1991.)
Primary repair of this condition consists of closing the VSD, establishing a continuity between the RV and the unifocalized PA (see below for unifocalization procedure) using either aortic or pulmonary homograft (9- to 10-mm internal diameter), and interrupting collateral circulation. The mortality rate varies between 5% and 20%. Good candidates for the repair are those with a Nakata index above 200. If the index is below 200, a shunt procedure is preferable.
b. Multiple-stage repair. When the requirements for single-stage repair are not met, three consequential steps are used to repair this condition. These steps are summarized in Figure 14-27.
(1) Stage 1. RV-to-hypoplastic PA conduit, using a relatively small homograft conduit (6- to 8-mm internal diameter) (see Fig. 14-27). The major goal of this operation is to make the central PA grow to an adequate size for eventual repair surgery. Interventional catheterization is carried out 3 to 6 months later to identify and coil occlude remaining aortic collaterals, to define PA distribution, and to identify if certain bronchopulmonary segments are receiving a duplicate blood supply.
(2) Stage 2. A unifocalization procedure is carried out. Unifocalization is a surgical procedure in which aortopulmonary collaterals are divided from their aortic origin and are anastomosed to the true pulmonary arteries or main PA conduit (see Fig. 14-27).
FIGURE 14-27 Diagram of multiple-stage repair. Upper row (confluent pulmonary artery [PA] and collaterals): A, A hypoplastic but confluent central PA and multiple other collateral arteries are shown. B, A small right ventricle–to–PA (RV-to-PA) connection is made with pulmonary homograft (shown shaded), with collaterals left alone. C, The pulmonary arteries have grown to a larger size, and a larger pulmonary homograft has replaced the earlier small one. Collateral arteries are now anastomosed (unifocalized) to the originally hypoplastic PA branches. The ventricular septal defect (VSD) may be closed at a later time usually 1 to 3 years of age. The pulmonary homograft is usually replaced with a larger graft at this time. Bottom row (nonconfluent PA and multiple collaterals): A, Absent central PA and multiple aortic collaterals are shown. B, A small pulmonary homograft (6–8 mm internal diameter, shown shaded) is used to establish the RV-to-PA connection with some collaterals connected to it (unifocalized) (performed at 3–6 mo). Some collaterals are not unifocalized at this time. C, The homograft conduit has been replaced with a larger one. Remaining collateral arteries are anastomosed to the pulmonary homograft to complete unifocalization procedure. The VSD is closed with or without fenestration, usually at 1 to 3 years.
Post-unifocalization catheterization is carried out 3 to 6 months later (a) to identify multiple peripheral stenosis in both the true as well as the unifocalized collaterals and to do balloon dilatation with or without stenting and (b) to assess the need for further unifocalization procedures.
(3) Stage 3. Closure of VSD with or without fenestration, usually at 1 to 3 years of age (see Fig. 14-27). The homograft conduit may need to be replaced at the same time. If the RV pressure is 10% to 20% greater than systemic pressure, a central fenestration 3 to 4 mm is created. Multiple ballooning and stenting procedures are often necessary to reduce RV pressure to less than 50% systemic if possible.
Surgical steps used in patients with TOF with pulmonary atresia are summarized in Figure 14-28.
Postoperative Follow-up
1. Frequent follow-up is needed to assess the palliative surgery and decide on appropriate times for further surgeries.
2. Valved conduits or homografts may develop valve degeneration requiring conduit replacement at a later time. Valvular stenosis can be dilated with a balloon to reduce the pressure gradient but often result in significant valve regurgitation, eventually leading to RV dysfunction. Many of these patients require surgical replacement of the conduit.
3. Recently, Bonhoeffer and his colleagues (2000) have developed a technique in which a dysfunctional conduit or homograft valve can be replaced by percutaneous replacement of pulmonary valve, and more children and adults have successfully had this procedure done (Khambadkone et al, 2005). A bovine jugular venous valve was mounted into the platinum stent and loaded in the delivery system. The assembly was delivered (implanted) in the RVOT according to standard stent-placing technique using an 18-Fr long sheath through a right femoral approach. This valve is marketed as the Melody transcatheter pulmonary valve. The other commercially available valve for use in the RVOT is the Edwards SAPIEN valve (Edwards Lifescience, Irvine, CA), a balloon-expandable stainless steel stent containing a bovine pericardial valve. Experience with this valve is extremely limited.
4. Survivors of the defect may need antibiotic prophylaxis for SBE for an indefinite period.
5. A certain level of activity restriction is needed because many of these children have exercise intolerance. Most survivors after complete repair are in New York Heart Association (NYHA) class I or II symptomatically.
FIGURE 14-28 Surgical approaches for tetralogy of Fallot with pulmonary atresia (or pulmonary atresia and ventricular septal defect [VSD]). MAPCAs, multiple aortopulmonary artery collaterals; PA, pulmonary artery; PBF, pulmonary blood flow; RV-PA, right ventricle–to–pulmonary artery.
Tetralogy of Fallot with Absent Pulmonary Valve
Prevalence
Tetralogy of Fallot with an absent pulmonary valve occurs in approximately 2% of patients with TOF.
Pathology and Pathophysiology
1. The pulmonary valve leaflets are either completely absent or have an uneven rim of rudimentary valve tissue present. The annulus of the valve is stenotic and displaced distally. A massive aneurysmal dilatation of the PAs is present. This anomaly is usually associated with a large VSD, similar to that seen in TOF. It rarely occurs with an intact ventricular septum.
2. The massive PA aneurysm (Fig. 14-29) develops during fetal life resulting from severe PR and an associated increase in RV stroke volume. The aneurysmal PAs compress anteriorly the lower end of the developing trachea and bronchi throughout fetal life, producing hypoplasia of the compressed airways. This produces signs of airway obstruction and respiratory distress during infancy. Pulmonary complications (e.g., atelectasis, pneumonia), rather than the intracardiac defect, are the usual causes of death.
3. The ductus arteriosus is frequently (but not invariably) absent in patients with more severe aneurysmal dilatation of the PAs.
4. Because the stenosis at the pulmonary valve ring is only moderate, an initial bidirectional shunt becomes predominantly a left-to-right shunt after the newborn period.
5. In some infants, tufts of PAs entwine and compress the intrapulmonary bronchi, resulting in reduced numbers of alveolar units. This may preclude successful surgical correction.
Clinical Manifestations
1. Mild cyanosis may be present as a result of a bidirectional shunt during the newborn period when the PVR is relatively high. Cyanosis disappears, and signs of CHF may develop after the newborn period. Respiratory symptoms vary greatly, ranging from neonates with severe respiratory compromise, those with wheezing or frequent respiratory infection, and those with no respiratory symptoms at all.
2. A to-and-fro murmur (with “sawing-wood” sound) at the upper and mid-left sternal borders is a characteristic auscultatory finding of the condition. This murmur occurs because of mild PS and free PR. The S2 is loud and single. The RV hyperactivity is palpable.
3. The ECG shows RAD and RVH.
FIGURE 14-29 A, Posteroanterior view of plain chest film showing hyperinflated areas in the left upper lobe and right lower portion of the chest in a 1-month-old infant who had tetralogy of Fallot with absence of the pulmonary valve. B, Anteroposterior view of pulmonary arteriogram showing massive aneurysmal dilatation of both the right and left pulmonary arteries.
4. Chest radiography images reveal a noticeably dilated main PA and hilar PAs. The heart size is either normal or mildly enlarged, and pulmonary vascular markings may be slightly increased. The lung fields may show hyperinflated areas, representing partial airway obstruction (see Fig. 14-29, A).
5. Echocardiographic studies reveal a large, subaortic VSD with overriding of the aorta, distally displaced pulmonary annulus (with thick ridges instead of fully developed pulmonary valve leaflets), and gigantic aneurysm of the PA and its branches. The RV is markedly dilated, often with paradoxical motion of the ventricular septum. Doppler studies reveal evidence of stenosis at the annulus and PR. Cardiac catheterization and angiocardiography (see Fig. 14-29, B) are usually unnecessary for accurate anatomic assessment of the PAs.
6. CT or MRI scan can define the relationship between sites of airway obstruction and dilatation of the central PA. Bronchoscopy provides the degree of airway compression.
Natural History
1. More than 75% of infants with severe pulmonary complications (e.g., atelectasis, pneumonia) die during infancy if treated only medically. The surgical mortality rate of infants with pulmonary complications is 20% to 40%.
2. Infants who survive infancy without serious pulmonary problems do well for 5 to 20 years and have fewer respiratory symptoms during childhood. They become symptomatic later and die from intractable right-sided heart failure.
Management
Medical
In the past, medical management was preferred because of poor surgical results in newborns; however, the mortality rate of medical management is much higher than surgical management. After the pulmonary symptoms appear, neither surgical nor medical management has good results.
Surgical
Symptomatic neonates should have corrective surgery on an urgent basis. Even asymptomatic children should have elective surgery in the first 3 to 6 month of life.
Primary Repair
Complete primary repair is the procedure of choice. VSD is closed through right ventriculotomy (across the pulmonary annulus). In symptomatic neonates, a pulmonary homograft is used to replace the dysplastic pulmonary valve and the dilated main and branch PAs. Alternatively, a valved conduit may be used to restore competence of the pulmonary valve, and the aneurysmal PAs are plicated. Some surgeons advocate aortic transection to achieve good exposure of the PAs for an extensive pulmonary arterioplasty into the hila of both lungs. An early surgical mortality rate is as high as more than 20% with a 1-year survival rate of 75%.
Total Anomalous Pulmonary Venous Return
Prevalence
Total anomalous pulmonary venous return (TAPVR) accounts for 1% of all CHDs. There is a marked male preponderance for the infracardiac type (male-to-female ratio of 4:1).
Pathology and Pathophysiology
1. No direct communication exists between the pulmonary veins and the LA. Instead, they drain anomalously into the systemic venous tributaries or into the RA. Depending on the drainage site of the pulmonary veins, the defect may be divided into the following four types (Fig. 14-30).
a. Supracardiac: This type accounts for 50% of TAPVR patients. The common pulmonary venous sinus drains into the right SVC through the left vertical vein and the left innominate vein (see Fig. 14-30, A).
b. Cardiac: This type accounts for 20% of TAPVR patients. The pulmonary veins enter the RA separately through four openings (only two openings are illustrated in Fig. 14-30, B), or the common pulmonary venous sinus drains into the coronary sinus (see Fig. 14-30, C).
c. Infracardiac: This type accounts for 20% of TAPVR patients. The common pulmonary venous sinus drains to the portal vein, ductus venosus, hepatic vein, or IVC. The common pulmonary vein penetrates the diaphragm through the esophageal hiatus (see Fig. 14-30, D).
d. Mixed type: This type, which is a combination of the other types, accounts for 10% of TAPVR patients.
FIGURE 14-30 Anatomic classification of total anomalous pulmonary venous return. A, Supracardiac. B and C, Cardiac. D, Infracardiac.
2. Many patients with supracardiac and cardiac types of TAPVRs and most patients with the infracardiac type have pulmonary hypertension secondary to obstruction of the pulmonary venous return. Either the length of the venous channels or the resistance caused by the hepatic sinusoids is the cause of obstruction.
3. In patients with pulmonary venous obstruction, pulmonary arterial hypertension develops. These patients develop progressive pulmonary venous congestion, hypoxemia, and systemic hypoperfusion.
4. An interatrial communication, either an ASD or PFO, is necessary for survival. Most patients do not have restricted flow across the atrial septum.
5. The left side of the heart is relatively small.
Clinical Manifestations
Clinical manifestations differ, depending on whether there is obstruction to the pulmonary venous return.
Without Pulmonary Venous Obstruction
History
1. CHF with growth retardation and frequent pulmonary infection is common in infancy.
2. A history of mild cyanosis from birth is present.
Physical Examination
1. The infant is undernourished and mildly cyanotic. Signs of CHF (e.g., tachypnea, dyspnea, tachycardia, hepatomegaly) are present.
2. A precordial bulge with hyperactive RV impulse is present. The cardiac impulse is maximal at the xyphoid process and the lower left sternal border.
3. Characteristic quadruple or quintuple rhythm is present. The S2 is widely split and fixed, and the P2 may be accentuated. A grade 2 to 3 of 6 ejection systolic murmur is usually audible at the upper left sternal border. A mid-diastolic rumble is always present at the lower left sternal border (because of increased flow through the tricuspid valve) (Fig. 14-31).
FIGURE 14-31 Cardiac findings of total anomalous pulmonary venous return without obstruction to pulmonary venous return.
FIGURE 14-32 Posteroanterior view of plain chest film demonstrating the “snowman” sign (A) and an angiocardiogram demonstrating anatomic structures that participate in the formation of the “snowman” sign (B). The vertical vein (left superior vena cava), the dilated left innominate vein, and the right superior vena cava are opacified.
Electrocardiography
Right ventricular hypertrophy of the so-called volume overload type (i.e., rsR′ in V1) and occasional RAH are present.
Radiography
1. Moderate to marked cardiomegaly involving the RA and RV is present with increased pulmonary vascular markings.
2. The “snowman” sign or figure-of-8 configuration may be seen in the supracardiac type but rarely before 4 months of age (Fig. 14-32).
With Pulmonary Venous Obstruction
History
1. Marked cyanosis and respiratory distress develop in the neonatal period with failure to thrive.
2. Cyanosis worsens with feeding, especially in infants with the infracardiac type, resulting from compression of the common pulmonary vein by the food-filled esophagus.
Physical Examination
1. Moderate to marked cyanosis and tachypnea with retraction are present in newborns and undernourished infants.
2. Cardiac findings may be minimal. A loud, single S2 and gallop rhythm are present. Heart murmur is usually absent. If present, however, it is usually a faint ejection-type systolic murmur at the upper left sternal border.
3. Pulmonary crackles and hepatomegaly are usually present.
Electrocardiography
Invariably, RVH in the form of tall R waves in the right precordial leads is present. RAH is occasionally present.
Radiography
The heart size is normal or slightly enlarged. The lung fields reveal findings of pulmonary edema (i.e., diffuse reticular pattern and Kerley’s B lines). These findings may be confused with pneumonia or hyaline membrane disease.
Echocardiography
Echocardiography and Doppler studies are usually diagnostic of the condition and can identify associated anomalies.
Features Common to All Types
1. A large RV with a compressed LV (i.e., relative hypoplasia of the LV) is the most striking initial finding. A large RA and a small LA, with deviation of the atrial septum to the left and dilated PAs, are also present.
2. An interatrial communication is usually present. PFO occurs in 70% of patients, and secundum ASD occurs in 30%.
3. A large common chamber (i.e., common pulmonary venous sinus) may be imaged posterior to the LA in the parasternal long-axis view.
4. M-mode echocardiography may show paradoxical or flat motion of the interventricular septum as a sign of RV volume overload.
5. Doppler studies reveal an increased flow velocity in the PA, an increased flow velocity or continuous flow at the site of the pulmonary venous drainage, and findings suggestive of pulmonary hypertension.
Features of the Supracardiac Type
The most common site of connection is the left SVC (i.e., left vertical vein), with subsequent drainage to the dilated left innominate vein and right SVC. These abnormal pathways can be imaged in the suprasternal notch short-axis view. Color-flow mapping and Doppler ultrasonography are helpful in defining the direction of the flow in the left SVC.
Features of the Cardiac Type
The most common site of entry is to the coronary sinus, occurring in 15% of cases. A dilated coronary sinus, best imaged in the parasternal long-axis view and the apical four-chamber view, may be the first clue to this condition.
Features of the Infracardiac Type
A dilated vein descending to the abdominal cavity through the diaphragm is imaged using the subcostal sagittal and transverse scans. All four pulmonary veins that connect to the confluence must be imaged. They are best imaged on the subcostal coronal scan or the suprasternal notch short-axis view.
Possibility of the Mixed Type
Unless it is demonstrated that all four pulmonary veins connect to the confluence, the possibility of the mixed type of TAPVR cannot be eliminated. In the most common mixed type, the left lung, usually the upper lobe, drains to the left SVC, and the remaining pulmonary veins in both lungs drain to the coronary sinus. When the mixed type is suspected, either MRI or cardiac catheterization needs to be performed.
Other Studies
Echocardiography is usually diagnostic and can identify the subtypes. Cardiac catheterization is rarely performed for diagnostic purposes; it is occasionally done to perform atrial septostomy to improve atrial shunt or to identify a complex mixed type of pulmonary venous return. Alternatively, MRI or cardiac CT can be used for diagnosis in case of complex mixed type; the former is preferable because it does not use ionizing radiation.
Natural History
1. CHF occurs in both types of TAPVRs with growth retardation and repeated pneumonias.
2. Without surgical repair, two thirds of the infants without obstruction die before reaching 1 year of age. They usually die from superimposed pneumonia.
3. Patients with the infracardiac type rarely survive for longer than a few weeks without surgery. Most die before 2 months of age.
Management
Medical
1. Intensive anticongestive measures with diuretics should be provided for infants without pulmonary venous obstruction.
2. Metabolic acidosis, if present, should be corrected.
3. Infants with severe pulmonary edema (resulting from the infracardiac type and from other types with obstruction) should be intubated and receive ventilator support with oxygen and positive end-expiratory pressure, if necessary, before cardiac catheterization or surgery.
4. In some patients with pulmonary hypertension, such as those with the infracardiac type, PGE1 can increase systemic flow by keeping the ductus open.
5. If the size of the interatrial communication appears small and immediate surgery is not indicated, balloon atrial septostomy or blade atrial septostomy may be performed to enlarge the communication.
Surgical
Indications and Timing
Corrective surgery is necessary for all patients with this condition. No palliative procedure exists.
1. All infants with pulmonary venous obstruction should be operated on soon after diagnosis in the newborn period.
2. Infants who do not have pulmonary venous obstruction but do have heart failure that is difficult to control are usually operated on between 4 and 6 months of age.
Procedures
Although procedures vary with the site of the anomalous drainage, all procedures are intended to redirect the pulmonary venous return to the LA (Fig. 14-33). Surgical techniques used vary from surgeon to surgeon; some use the RA approach to reach the LA, and others reach the posterior wall of the LA directly. Some favor use of deep hypothermic (18°–20°C) circulatory arrest.
Supracardiac type. A large, side-to-side anastomosis is made between the common pulmonary venous sinus and the LA. The vertical vein is ligated. The ASD is closed with a cloth patch (see Fig. 14-33, A).
TAPVR to the RA. The atrial septum is excised, and a patch is sewn in such a way that the pulmonary venous return is diverted to the LA (see Fig. 14-33, B). The ASD may have to be enlarged.
TAPVR to the coronary sinus. An incision is made in the anterior wall of the coronary sinus (“unroofing”) to make a communication between the coronary sinus and the LA. A single patch closes the original ASD and the ostium of the coronary sinus. This results in the drainage of coronary sinus blood with low oxygen saturation into the LA (see Fig. 14-33, C).
Infracardiac type. A large vertical anastomosis is made between the common pulmonary venous sinus and the LA. The common pulmonary vein, which descends vertically to the abdominal cavity, is ligated above the diaphragm (see Fig. 14-33, D).
FIGURE 14-33 Surgical approaches to various types of total anomalous pulmonary venous returns. A, In the supracardiac type, a large side-to-side anastomosis is made between the common pulmonary venous sinus and the LA and the ASD is closed with a patch. B, in the cardiac type, the atrial septum is excised and a patch is sewn in such a way that all pulmonary venous return is diverted to the LA. C, for the coronary sinus type, an incision is made in the anterior wall of the coronary sinus to make a communication between the coronary sinus and the LA. The original ASD and the ostium of the coronary sinus are closed by a single patch. D, for the infracardiac type, a large anastomosis is made between the common pulmonary venous sinus and the LA and the common pulmonary vein is ligated above the diaphragm.
Mortality rate. The surgical mortality rate is between 5% and 10% for infants with the unobstructed type. This rate can be as high as 20% for infants with the infracardiac type. Two common causes of death are postoperative paroxysms of pulmonary hypertension and the development of pulmonary vein stenosis.
Complications
1. Paroxysms of pulmonary hypertension, which relate to a small and poorly compliant left heart, with resulting cardiac failure and pulmonary edema, may require prolonged respiratory support postoperatively.
2. Postoperative arrhythmias are usually atrial.
3. Obstruction at the site of anastomosis or stenosis of the pulmonary veins rarely occurs.
Postoperative Follow-up
1. An office evaluation every 6 to 12 months is recommended for such late complications as pulmonary vein obstruction and atrial arrhythmias.
2. Pulmonary vein obstruction at the anastomosis site or delayed development of pulmonary vein stenosis may occur in about 10% of patients and requires reoperation. These complications are usually evident within 6 to 12 months after the repair. The possibility of pulmonary vein stenosis requires cardiac catheterization and angiocardiography. If present, it is nearly impossible to correct.
3. Some patients develop atrial arrhythmias, including sick sinus syndrome, that require medical treatment or pacemaker therapy.
4. Activity restriction is usually unnecessary unless pulmonary venous obstruction occurs.
Tricuspid Atresia
Prevalence
Tricuspid atresia accounts for 1% to 3% of CHDs.
Pathology
1. The tricuspid valve is absent, and the RV is hypoplastic, with absence of the inflow portion of the RV. The associated defects such as ASD, VSD, or PDA are necessary for survival.
2. Tricuspid atresia is usually classified according to the presence or absence of PS and TGA (Fig. 14-34). The great arteries are normally related in about 70% of cases and are transposed in 30% of cases. In 3% of cases, the L form of transposition occurs.
3. In patients with normally related great arteries, the VSD is usually small, PS is present with resulting hypoplasia of the pulmonary arteries, and the pulmonary blood flow is reduced. This is the most common type, occurring in about 50% of all patients with tricuspid atresia. Occasionally, the VSD is large with normal-sized PAs or the ventricular septum is intact with pulmonary atresia.
4. When TGA is present, the pulmonary valve is normal with increased PBF in two thirds of cases. In one third of cases, it is either stenotic or atretic with decreased PBF. Patients with TGA need a fairly large VSD to maintain normal systemic cardiac output. Less than adequate size or spontaneous reduction of the VSD creates problems with a decreased systemic cardiac output.
5. COA or interrupted aortic arch is a frequently associated anomaly that is more commonly seen in patients with TGA.
Clinical Manifestations
History
1. Cyanosis is usually severe from birth. Tachypnea and poor feeding usually manifest.
2. History of hypoxic spells may be present in infants with this condition.
FIGURE 14-34 Anatomic classification of tricuspid atresia. In about 70% of cases, the great arteries are normally related, and there is a small ventricular septal defect (VSD) with associated hypoplasia of the pulmonary artery (PA). When the great arteries are transposed, the VSD is usually large, and the PAs are large with increased pulmonary blood flow. AS, aortic stenosis; D-TGA, complete transposition of the great arteries; L-TGA, congenitally corrected TGA; PA, pulmonary atresia; PS, pulmonary stenosis; sub AS, subaortic stenosis; sub PS, subpulmonary stenosis; TGA, transposition of the great arteries; VSD, ventricular septal defect. (Data from Keith JD, Rowe RD, Vlad P: Heart Disease in Infancy and Childhood, 3rd ed. New York, Macmillan, 1978.)
FIGURE 14-35 Cardiac findings of tricuspid atresia associated with patent ductus arteriosus and ventricular septal defect. “Superior” QRS axis on the electrocardiogram and cyanosis are characteristic of the defect.
Physical Examination (Fig. 14-35)
1. Cyanosis is usually present. Older infants may have clubbing.
2. A systolic thrill is rarely palpable when associated with PS.
3. The S2 is single. A grade 2 to 3 of 6 holosystolic (or early systolic) murmur of VSD is usually present at the lower left sternal border. A continuous murmur of PDA is occasionally present. An apical diastolic rumble is rarely audible in patients with large PBF.
4. Hepatomegaly may indicate an inadequate interatrial communication or CHF.
FIGURE 14-36 Tracing from a 6-month-old girl with tricuspid atresia showing “superior QRS axis” or left anterior hemiblock (–30 degrees), right atrial hypertrophy, and left ventricular hypertrophy.
FIGURE 14-37 Posteroanterior view of chest roentgenogram in an infant with tricuspid atresia with normally related great arteries. The heart is minimally enlarged. The pulmonary vascular markings are decreased, and the main pulmonary artery segment is somewhat concave.
Electrocardiography
1. “Superior” QRS axis (between 0 and –90 degrees) is characteristic. It appears in most patients without TGA (Fig. 14-36). The “superior” QRS axis is present in only 50% of patients with TGA.
2. LVH is usually present; RAH or biatrial hypertrophy is common.
Radiography
The heart size is normal or slightly increased, with enlargement of the RA and LV. Pulmonary vascularity decreases in most patients (Fig. 14-37), although it may increase in infants with TGA. Occasionally, the concave PA segment may produce a boot-shaped heart, similar to the radiographic findings of TOF.
Echocardiography
Two-dimensional echocardiography readily establishes the diagnosis of tricuspid atresia.
1. Absence of the tricuspid orifice, a large RA, marked hypoplasia of the RV, and a large LV can be imaged in the apical four-chamber view. The size of the LA is determined by the magnitude of pulmonary blood flow.
2. The bulging of the atrial septum toward the left and the size of the interatrial communication are easily imaged in the subcostal four-chamber view.
3. The size of the VSD, the presence and severity of PS, and the presence of TGA should all be investigated.
4. Patients with TGA should be examined for possible subaortic stenosis and aortic arch anomalies, especially the COA.
Other Studies
Echocardiographic and color-flow Doppler studies can delineate most anatomic and physiologic issues related to the condition. However, cardiac catheterization with interventional balloon atrial septostomy is indicated when atrial communication is inadequate. Cardiac catheterization is generally recommended before a planned surgical intervention other than the BT shunt or PA banding. Specific information on the PA anatomy, pressure, and LV function is necessary before any Fontan-type operation.
Natural History
1. Few infants with tricuspid atresia and normally related great arteries survive beyond 6 months of age without surgical palliation.
2. Occasionally, patients with increased PBF develop CHF and eventually pulmonary vascular obstructive disease.
3. For patients who survive into their second decade of life without a Fontan-type operation, the chronic volume overload of the LV usually results in LV systolic dysfunction, which is a known risk factor for the Fontan operation. (The Fontan procedure should be performed before LV dysfunction develops.)
Management
Initial Medical Management
1. PGE1 should be started in neonates with severe cyanosis to maintain the patency of the ductus before planned cardiac catheterization or cardiac surgery.
2. The Rashkind procedure (balloon atrial septostomy) may be performed as part of the initial catheterization to improve the RA-to-LA shunt, especially when the interatrial communication is considered inadequate by echocardiographic studies.
3. Treatment of CHF is rarely needed in infants with TGA and without PS.
4. Infants with normally related great arteries and adequate PBF through a VSD do not need any other procedures; rather, they need to be closely watched for decreasing oxygen saturation resulting from spontaneous reduction of the VSD.
Surgical
Most infants with tricuspid atresia require one or more palliative procedures before a Fontan-type operation, the definitive surgery, can be performed. Staged palliative surgical procedures are aimed at producing ideal candidates for future Fontan candidates. Ideal candidates for a Fontan-type operation are those who have normal LV function and low pulmonary resistance.
1. Normal LV function results from prevention of excessive volume or pressure loading of the LV by:
a. Preventing excessive volume load by using a relatively small systemic-to-pulmonary shunt (e.g., 3.5 mm for neonates).
b. Avoiding ventricular hypertrophy (e.g., by relieving the LV outflow obstruction).
2. Low pulmonary resistance may result from:
a. Providing adequate PBF, which promotes the growth of PA branches (with a resulting increase in the cross-sectional area of the pulmonary vascular bed).
b. Preventing distortion of the central pulmonary arteries. Shunt operation is preferably done on the right PA, which can be incorporated into a Fontan operation.
c. Protecting the pulmonary vascular bed from overflow or pressure overload (by PA band when PBF is increased).
Palliative surgical procedures described below and the Fontan procedure are not just for tricuspid atresia but are also performed for other CHDs with a functionally single ventricle, such as single ventricle (double inlet ventricle), some cases of pulmonary atresia with an intact ventricular septum, unbalanced AV canal, complicated DORV, HLHS, and heterotaxia (splenic syndromes). Because the Fontan operation is applicable to so many other defects, a staged approach to the Fontan operation is summarized in Box 14-2 for quick reference.
Stage 1. The most frequently performed first-stage operation is the BT shunt. Under special circumstances, other procedures (e.g., the Damus-Kaye-Stansel operation) may have to be combined with the BT shunt. On rare occasion, a PA banding is indicated for infants with too much pulmonary blood flow.
1. BT shunt. Most patients who have tricuspid atresia with decreased PBF need the BT shunt soon after birth when the PVR is still high (see Fig. 14-22). This procedure results in the volume load on the LV because the LV supplies blood to both the systemic and pulmonary circulations. Thus, the shunt should be relatively small (e.g., 3.5 mm) and should not be left alone too long (before proceeding to stage 2 operation). The B-T shunt is done on the right PA.
2. Damus-Kaye-Stansel and shunt operation. For infants with tricuspid atresia with TGA and restrictive VSD, the Damus-Kaye-Stansel procedure may be performed in addition to a systemic-to-PA shunt. In the Damus-Kaye-Stansel operation, the main PA is transected, and the distal PA is sewn over. The proximal PA is connected end to side to the ascending aorta (see Fig. 14-11). A systemic-to-PA shunt is created to supply blood to the lungs. A Fontan-type operation is performed at a later time. This procedure also results in the volume overload to the LV, and a stage 2 operation should be performed as early as possible.
3. PA banding. PA banding is rarely necessary for infants with CHF resulting from increased PBF. PA banding protects the pulmonary vasculature from developing pulmonary hypertension, and it may be performed at any age with a mortality rate of less than 5%.
Follow-up Medical Management. After the stage 1 operation, the infant should be watched carefully until the time of the stage 2 palliation with emphasis on the following.
a. Cyanosis (with O2 saturation <75%) should be investigated by cardiac catheterization or MRI.
b. Poor growth may indicate too large a PBF. and tightening of the PA band should be considered.
BOX 14-2 Fontan Pathway
Stage I One of the following procedures is done in preparation for a future Fontan operation.
1. The Blalock-Taussig shunt, when PBF is small
2. PA banding when PBF is excessive
3. Damus-Kaye-Stansel + shunt operation (for TA + TGA + restrictive VSD)
Medical follow-up after stage I. Watch for:
a. Cyanosis (O2 saturation <75%): cardiac catheterization or MRI to find out the cause of it
b. Poor weight gain (CHF from too much PBF): tightening of PA band may be necessary
Stage II (at 3 mo or by 6 mo)
1. BDG operation or
2. The hemi-Fontan operation
Medical follow-up after stage II. Watch for the following:
a. A gradual decrease in O2 saturation (<75%) may be caused by:
(1) Opening of venous collaterals
(2) Pulmonary AV fistula (caused by the absence of hepatic inhibitory factor): Perform cardiac catheterization (to find and occlude collaterals) or proceed with Fontan operation.
b. Transient hypertension: 1–2 wk postoperatively: May use ACE inhibitors
c. Cardiac catheterization by 12 mo after stage II.
The following are risk factors. Presence of ≥2 is a high-risk situation.
(1) Mean PA pressure >18 mm Hg (or PVR >2 U/m2)
(2) LV end-diastolic pressure <12 mm Hg (or EF >60%)
(3) AV valve regurgitation
(4) Distorted PAs secondary to previous shunt operation
Stage III (Fontan operation): within 1–2 yr after stage II operation
1. “Lateral tunnel” Fontan (with 4 mm fenestration)
2. An extracardiac conduit (with or without fenestration)
ACE, angiotensin-converting enzyme; AV, atrioventricular; CHF, congestive heart failure; EF, ejection fraction; LV, left ventricle; MRI, magnetic resonance imaging; PA, pulmonary artery; PBF, pulmonary blood flow; PVR, pulmonary vascular resistance; TA, truncus arteriosus; TGA, transposition of the great arteries; VSD, ventricular septal defect.
Stage 2. As a stage 2 operation, either a bidirectional Glenn shunt or the hemi-Fontan operation is performed in preparation for the final Fontan operation.
1. Bidirectional Glenn operation. An end-to-side SVC-to-RPA shunt (also called bidirectional superior cavopulmonary shunt) can be performed by 2.5 to 3 months of age (Fig. 14-38, A). By this time, the PVR is sufficiently low to allow venous pressure to be the driving force for the pulmonary circulation. There appears to be no advantage in further delaying the second stage operation beyond 6 months. For this procedure to be successful, the PVR has to be relatively low because the SVC blood flows passively into the pulmonary arteries. Any previous systemic-to-PA shunt is taken down at the time of the procedure. The azygos vein and, when present, the hemiazygos are divided. The IVC blood still bypasses the lungs.
This procedure satisfactorily increases oxygen saturation, which averages 85%, without adding volume work to the LV. The mortality rate for this procedure is between 5% and 10%.
2. The hemi-Fontan operation. An incision is made along the most superior part of the RA appendage, and it is extended into the SVC (Fig. 14-39). A connection is made between this opening and the lower margin of the central portion of the PA. An intraatrial baffle is placed to direct the SVC blood to the pulmonary arteries. The BT shunt is taken down, and the native pulmonary valve is oversewn.
FIGURE 14-38 A modified Fontan operation. A, Bidirectional Glenn operation or superior vena cava (SVC)–to–right pulmonary artery anastomosis (state 2 operation). B, Completion of the Fontan operation by cavocaval baffle–to–pulmonary artery (PA) connection, with or without fenestration (stage 3 operation). See text for description of these procedures. AO, aorta; IVC, inferior vena cava; LV, left ventricle; RA, right atrium; RV, right ventricle.
FIGURE 14-39 Hemi-Fontan operation. A, A Blalock-Taussig (BT) shunt is taken down (arrow). An incision is made in the superior aspect of the right atrial appendage (RAA) extending it into the superior vena cava (SVC), and a horizontal incision is made in the right pulmonary artery (RPA). B, The lower margin of the RPA incision and the adjacent margin of the incision in the RAA and SVC are connected. C, The connection is completed using pulmonary allograft. An intraatrial patch is placed to direct SVC blood to the pulmonary arteries. AO, aorta; RA, right atrium.
The advantages of the hemi-Fontan operation are that it allows supplementation of the central PA area so as to optimize flow to the left lung, and it simplifies the subsequent Fontan operation. A major disadvantage may be that it involves extensive surgery in the region of the sinus node and sinus node artery, which may result in late sinus node dysfunction.
Medical follow-up after the stage 2 operation should focus on the following (see Box 14-2).
a. A remarkable improvement in O2 saturation (≈85%) results after the procedure. However, a gradual deterioration in O2 saturation may occur in the months after surgery, which may be caused by:
1) Opening of venous collaterals which decompress the upper body
2) The development of pulmonary arteriovenous fistula, which may be related to an absence of hepatic inhibitory factor
Pulmonary arteriovenous fistulas develop commonly after the SVC-to-PA connection, in which hepatic venous blood does not reach the pulmonary circulation. It has been postulated that the liver may produce vasoconstrictor PGs, which prevent pulmonary vasodilation and development of pulmonary arteriovenous fistula. Vasoconstrictor PGs in blood from the liver bypassing the pulmonary circulation may lead to the pulmonary arteriovenous fistulas. Song and colleagues (1996) reported that long-term aspirin (a cyclooxygenase inhibitor) therapy has successfully prevented the development of cyanosis, possibly by preventing pulmonary arteriovenous fistula formation. A similar pulmonary arteriovenous fistula also occurs, with the clinical manifestation of cyanosis in patients with liver dysfunction (hepatopulmonary syndrome). The diagnosis of pulmonary arteriovenous malformation requires pulmonary angiography or, even better, a bubble-contrast echocardiography with injection into branch pulmonary arteries.
b. If a child’s O2 saturation is 75% or less, it is preferable to proceed with Fontan operation. Alternatively, cardiac catheterization may be performed to find a cause of desaturation (e.g., missed left SVC, which can be coil occluded).
c. A pre-Fontan cardiac catheterization is performed by 12 months after the second-stage operation.
Stage 3. A modified Fontan operation is the definitive procedure for patients with tricuspid atresia. The whole premise of the Fontan operation is directing the entire systemic venous blood to the pulmonary arteries without an intervening pumping chamber. The Fontan operation is usually completed when the child is around 2 years of age. This procedure can even be performed on infants.
The following are risk factors for the Fontan operation: The presence of two or more of these risk factors constitutes a high-risk situation.
a. High PVR (>2 U/m2) or high mean PA pressure (>18 mm Hg)
b. Distorted PAs secondary to previous shunt operations
c. Poor systolic or diastolic ventricular function, with LV end-diastolic pressure greater than 12 mm Hg or an ejection fraction less than 60%
d. AV valve regurgitation
The surgical technique of completing a modified Fontan operation varies according to the type of the second-stage operation performed (bidirectional Glenn operation or hemi-Fontan operation).
1. After the bidirectional Glenn procedure
An intraatrial tubular pathway is created from the orifice of the IVC to the orifice of the SVC (termed cavocaval baffle or a lateral tunnel). The cardiac end of the SVC is anastomosed to the undersurface of the RPA to complete the operation (see Fig. 14-38, B).
Some centers routinely use “fenestration” (4–6 mm) in the baffle, but others use it only in high-risk patients. The fenestration needs to be closed later, usually with an ASD closure device in the catheterization laboratory. Cited advantages of fenestration include decompression of the systemic venous circulation and augmentation of cardiac output in the early postoperative period. Disadvantages include systemic arterial desaturation with possible systemic embolization from the systemic veins and the later need to close the fenestration. An alternative to the above-described procedure, an extracardiac conduit, may be used to complete the Fontan operation (see Fig. 14-41, H). Fenestration is not necessary for the extracardiac conduit, but some surgeons create the fenestration with this approach.
FIGURE 14-40 From the hemi-Fontan to Fontan connection. A, A vertical incision (heavy broken line) is made in the anterior right atrial (RA) wall. B, The intraatrial patch is removed, and a lateral tunnel is constructed to direct the inferior vena cava (IVC) blood to the existing conglomerate of RA and right pulmonary artery (RPA). C, The direction of blood flow from the superior vena cava (SVC) and IVC is shown.
Early survival rates have improved to more than 90%. In a large series of 500 Fontan operations, the probability of survival was 85% at 1 month, about 80% at 1 and 5 years, and 70% at 10 years.
2. After the hemi-Fontan operation
The intraatrial patch that was used to direct SVC blood to the PAs is excised, and a lateral atrial tunnel is constructed, directing flow from the IVC to the previously created amalgamation of the SVC with the RPA (Fig. 14-40).
Timing for surgery is the same as for the cavocaval baffle-to-PA anastomosis. The mortality rate for the Fontan procedure for children who have undergone a hemi-Fontan operation is reportedly lower than those who had the bidirectional Glenn operation.
Complications of the Fontan-Type Operation
Early Complications.
Early postoperative complications may include the following.
1. Low cardiac output, heart failure, or both are early postoperative complications.
2. Persistent pleural effusion. This is a troublesome complication. Prolonged pleural drainage may lead to protein-losing enteropathy, which carries a poor prognosis. It may be the result of a sudden rise in the systemic venous or RA pressure. It occurs more often on the right side. The presence of aortopulmonary collaterals increases the risk of prolonged pleural effusion. Coil occlusion of these vessels before surgery can ameliorate this problem.
The extracardiac conduit was associated with increased pleural drainage than the intraatrial lateral tunnel, although the former may have a theoretical benefit for a lower incidence of late arrhythmias (Rogers et al, 2012). On the other hand, creation of fenestration was associated with a decreased incidence of prolonged effusion. Among patients who received extracardiac conduit, Gupta et al (2008) found that lower preoperative oxygen saturation, smaller conduit size, and longer duration of cardiopulmonary bypass were associated with persistent pleural effusion.
The following treatments can be used for this complication: prolonged chest tube drainage, a low-fat diet with a medium-chain triglyceride oil supplement or total parenteral nutrition, chemical or talc pleurodesis, a pleuroperitoneal shunt, and thoracic duct ligation (which is a major surgery).
3. Thrombus formation in the systemic venous pathways may result from a sluggish blood flow, which can be diagnosed by transesophageal echocardiography. Treatment consists of warfarin, thrombolysis with streptokinase, or surgical removal. The risk is highest in the first several weeks to months after the Fontan operation, although the risk is present for the lifetime.
4. Although rare, acute liver dysfunction with alanine transaminase (ALT) greater than 1000 U/L can occur during the first week after surgery, possibly resulting from hepatic hypoperfusion (caused by low cardiac output).
Late Complications.
Regular follow-up is necessary to detect the following late complications:
1. Prolonged hepatomegaly and ascites require treatment with diuretics, afterload-reducing agents, and digitalis.
2. Supraventricular arrhythmia is one of the most troublesome complications. Early-onset arrhythmias occur in 15% of patients. The incidence of late-onset supraventricular arrhythmia continues to increase with longer follow-up after the Fontan procedure (6% at 1 year, 12% at 3 years, and 17% at 5 years). Extracardiac conduit (instead of intraatrial lateral tunnel) may help reduce the incidence of late cardiac arrhythmias (see Fig. 14-41, H).
3. A progressive decrease in arterial oxygen saturation may result from obstruction of the venous pathways, leakage in the intraatrial baffle, or development of pulmonary arteriovenous fistula.
4. Protein-losing enteropathy can result from increased systemic venous pressure that subsequently causes lymphangiectasis. Prolonged pleural drainage is an unfavorable sign to develop this condition. Increased PVR, decreased cardiac index, and increased ventricular end-diastolic pressure were coincidental findings with the condition. The incidence of protein-losing enteropathy among survivors is 4%. The prognosis is poor; about half of patients die within 5 years, regardless of the type of treatment, medical or surgical. Heart transplantation should be considered for these patients.
5. Thromboembolism can occur in up to 10% of patients after the Fontan operation. Some reports suggest stroke occurring in as high as 19% of the patients. Therefore, long-term thromboprophylaxis is required (see below).
The following are considered an increased risk for thromboembolism: a known hypercoagulable state, presence of intracardiac prosthetic materials, intracardiac shunt (fenestration), dilated atrium, atrial arrhythmias, ventricular dysfunction, low-flow states, stasis in the venous pathways, protein-losing enteropathy, and PA distortion. The use of an extracardiac conduit may reduce the risk of thromboembolism.
Results of Fontan Operation
Currently, the operative mortality rate of the Fontan procedure is less than 3%. Mean PA pressure of 15 mm Hg or above was associated with prolonged hospital stay and unfavorable outcomes (Rogers et al, 2012). The overall survival rate after the Fontan operation is above 95% at follow-up of 50 months (Hirsch et al, 2008).
Postoperative Medical Follow-up
1. Patients should maintain a low-salt diet.
2. Medications
a. Some patients need continued digoxin and diuretic therapy.
b. An angiotensin-converting enzyme (ACE) inhibitor is generally recommended. Although not proved, it may augment LV output with consequent improvement in pulmonary blood flow.
c. Aspirin or even warfarin is used to prevent thrombus formation. Controversy exists as to whether aspirin is adequate for thrombus prophylaxis compared with warfarin. A recent international report suggests that aspirin (5 mg/kg/day) is as good as properly controlled warfarin therapy (with a target international normalized ratio [INR] of 2.0–3.0) (McCrindle et al, 2013). Earlier studies have also reported the same finding. An important new finding by McCrindle et al (2013) is that when the INR levels were inadequately controlled (<2.0), the risk of thrombosis was higher than with aspirin. Anticoagulation activity is minimal with an INR below 2.0, and it is almost nonexistent with an INR below 1.5. Achieving and maintaining a target level of INR (>2.0) is important but difficult, especially in children, because of individual and genetic factors, interactions with multiple drugs and foods, and noncompliance. The ease of aspirin administration and the attendant higher compliance appear to make the antiplatelet dose of aspirin a better choice than warfarin.
3. Some centers recommend device closure of the fenestration a year or so after the Fontan procedure. However, about 20% to 40% of fenestrations will close spontaneously over the first year or two postoperatively.
4. Patients should not participate in competitive, strenuous sports.
5. Antibiotic prophylaxis against SBE should be observed when indications arise.
6. Among patients with tricuspid atresia, the 5-year survival rate is 80%, and the 10-year survival rate is 70%. During years 11 to 16 after surgery, the majority of patients have shown acceptable results, with 48% in NYHA class I, and 16% in class II (see Appendix A, Table A-3).
Evolution of the Fontan-Type Operation
The Fontan-type operation applies to many complex CHDs, most of which are otherwise uncorrectable. Therefore, this procedure can be considered a major advancement in pediatric cardiac surgery during the past 4 decades. Castaneda (1992) has written an excellent review article on the historical aspect of the Fontan-type operations. Many modifications have been made since the original Fontan operation in 1971. The results of animal experiments conducted in the 1940s and 1950s suggested that the RV could be successfully bypassed (i.e., systemic venous pressure was an adequate force for pulmonary blood flow). The Glenn shunt (1958), which is an end-to-end anastomosis of the SVC to the distal end of the right PA, was the first such example, although it involved only one lung.
The original Fontan operation consisted of a Glenn shunt, connection of the RA and the right PA with insertion of an aortic homograft, insertion of another allograft valve in the IVC–RA junction, and closure of the ASD (Fig. 14-41, A). At that time, RA contractions were thought to be important in pulsatile assistance to the pulmonary circulation. It became evident later that inlet and outlet valves were more problematic than beneficial.
Kreutzer and associates (1973) made a direct anastomosis between the RA appendage and the PA trunk using either a homograft or the patient’s own pulmonary valve. The ASD was closed (see Fig. 14-41, B). Subsequently, modifications of the connection were made between the RA and RV (see Fig. 14-41, C), as well as between the RA and the main or right PA (see Fig. 14-41, D), by direct anastomosis of the two structures or by the use of patches or conduits with or without an interposed valve. It became evident later that a direct connection between the RA appendage and the right PA without an interposed valve provided equally good hemodynamic results and that the incorporation of a portion of the RV was not beneficial.
Kawashima and associates (1984) reported a new operation in four children with complex single ventricle. These children also had interrupted IVC with either azygous continuation to the right SVC or hemiazygous continuation to the left SVC and they were palliated earlier with B-T shunts. Either the right or left SVC, which received blood from the entire systemic venous system, was successfully connected end to side to the ipsilateral PAs (in Fig. 14-41, E, azygous continuation is shown). This procedure proved for the first time that the entire systemic venous return could be put into the pulmonary circulation, completely bypassing the right side of the heart.
De Leval and associates (1988) have shown that the interposition of a compliant RA chamber between the systemic vein and the PA is a major cause of energy loss in the RA, and they have shown that a cavocaval baffle-to-PA anastomosis, the latest modification of the Fontan operation (see Fig. 14-41, F), has significant hemodynamic advantages over earlier attempts to use the RA (as in Fig. 14-41, D) as part of the venous pathway.
A two-stage Fontan operation was recommended for high-risk patients. Initially, a bidirectional Glenn shunt was performed. This was later followed by the completion of the cavocaval baffle-to-right PA anastomosis. After the first procedure, there was often a noticeable improvement in oxygen saturation and symptoms to the point that raised questions about the necessity of the second procedure.
FIGURE 14-41 Modifications of the Fontan operation. A, The original Fontan operation (Fontan and Baudet, 1971) consisted of an end-to-end anastomosis of the right pulmonary artery (RPA) to the superior vena cava (SVC), an end-to-end anastomosis of the right atrial appendage (RAA) to the proximal end of the RPA by means of an aortic valve homograft, closure of the atrial septal defect (ASD), insertion of a pulmonary valve homograft into the inferior vena cava (IVC), and ligation of the main pulmonary artery (PA). B, Modification by Kreutzer et al (1973)consisted of an anastomosis of the RAA and the main PA with its intact pulmonary valve (which was excised from the right ventricle [RV]) after closure of the ASD and ventricular septal defect. A Glenn operation was not performed, and no IVC valve was used. C, A later modification by Bjork et al (1979) consisted of a direct anastomosis between the RAA and the right ventricular outflow tract in patients with a normal pulmonary valve using a roof of pericardium to avoid a synthetic tube graft. D, Direct anastomosis of the right atrium (RA) to the RPA. E, Kawashima et al (1983) first showed that systemic venous returns could be directly connected to the pulmonary circulation without passing through the right heart. F and G, Separate anastomosis of the two ends of the divided SVC to the RPA and insertion of IVC to SVC intraatrial baffle (total cavopulmonary connection) with (G) and without (F) fenestration. H, Extracardiac conduit between the IVC and the RPA and a bidirectional Glenn operation. AO, aorta; LPA, left pulmonary artery; LV, left ventricle.
A fenestrated Fontan operation has been recommended for high-risk patients (see Fig. 14-41, G). Reported advantages of fenestration include a lower early surgical mortality rate; reduced incidence or duration of postoperative pleural effusion; shorter hospital stay; and right-to-left shunt through the fenestration, which may help maintain cardiac output if blood flow through the lungs decreases. The possible disadvantages are paradoxical embolization and stroke, lower arterial oxygen saturation, and the need to close the fenestration.
Extracardiac right heart bypass with an IVC-to-right PA Dacron conduit and SVC-to-PA PA anastomosis has also been performed (see Fig. 14-41, H). This procedure is performed a little later than the standard intraatrial lateral tunnel operation in order to place a larger conduit. An extracardiac conduit appears to be better than the intraatrial lateral tunnel procedure with a very low operative mortality rate, a lower incidence of early and late arrhythmias, improved hemodynamics, and fewer postoperative complications (Backer et al, 2011), but the conduit does not have growth potential. However, a recent report by Rogers et al (2012) found an association between extracardiac conduit and prolonged period of pleural drainage.
Surgical approaches in tricuspid atresia are summarized in Figure 14-42.
Pulmonary Atresia with Intact Ventricular Septum
Prevalence
Pulmonary atresia with an intact ventricular septum accounts for fewer than 1% of all CHDs. It accounts for 2.5% of the critically ill infants with CHDs.
FIGURE 14-42 Surgical approaches in tricuspid atresia. BDG, bidirectional Glenn; BT, Blalock-Taussig; op, operation; PA, pulmonary artery; PBF, pulmonary blood flow; TA, tricuspid atresia; TGA, transposition of the great arteries; VSD, ventricular septal defect.
FIGURE 14-43 Schematic diagrams of right ventriculograms that illustrate three types of pulmonary atresia with intact ventricular septum. A, Normal right ventricle (RV). B, Tripartite type that shows all three portions (inlet, trabecular, and infundibular) of the RV. C,Bipartite type in which only the inlet and infundibular portions are present. D, Monopartite type in which only the inlet portion of the RV is present.
Pathology
1. In 80% of these patients, the pulmonary valve is atretic with a diaphragm-like membrane. The infundibulum is atretic in 20% of these patients. The valve ring and the main PA are hypoplastic. The PA trunk is rarely atretic. The ventricular septum remains intact.
2. RV size varies and relates to survival. In 1982, Bull and associates divided this condition into three types based on the presence or absence of the three portions of the RV: inlet, trabecular, and infundibular portions (Fig. 14-43). All three of these portions are present, and the RV is almost normal in size in the tripartite type of pulmonary atresia. In the bipartite type, the inlet and infundibular portions are present, but the trabecular portion is obliterated. The inlet is the only portion present, and the RV size is diminutive in the monopartite type. The RV size is highly correlated with the size of the tricuspid valve. A rare type of pulmonary atresia that is not included in the above classification is that associated with tricuspid insufficiency, less thickened but dilated RV cavity, and dilated RA.
3. This condition is frequently associated with important anomalies of the coronary arteries. The high pressure in the RV is decompressed through dilated coronary microcirculation (i.e., ventriculocoronary connection, coronary sinusoids, or RV-dependent coronary circulation) into the left or right coronary artery (see Fig. 14-44 for right ventriculograms showing coronary sinusoids). Often the proximal coronary arteries are obstructed (≈10%). Rarely, proximal portion(s) of the right or left coronary artery are absent. Sinusoid channels are demonstrable by a right ventriculogram in 30% to 50% of cases. If proximal coronary artery obstruction is present, coronary circulation is perfused entirely by desaturated RV blood (RV-dependent coronary circulation). Tricuspid valve z score less than –2.5 is a helpful predictor of coronary fistulas and RV-dependent coronary circulation. Such coronary sinusoids occur only in patients with hypertensive RV and not in patients with tricuspid regurgitation.
4. Confluent pulmonary arteries are usually present with PBF provided through a PDA. Rarely, nonconfluent pulmonary arteries are supplied by bilateral ductus arteriosus or multiple aortopulmonary collaterals.
5. An interatrial communication (i.e., either ASD or PFO) and PDA (or collateral arteries) are necessary for the patient to survive.
6. RV myocardium shows varying degrees of ischemia, infarction, fibrosis, and endocardial fibroelastosis, with poorly compliant RV, which may contribute to surgical mortality.
Clinical Manifestations
History
A history of severe cyanosis since birth is present.
Physical Examination
1. Severe cyanosis and tachypnea are seen in distressed neonates.
2. The S2 is single. A heart murmur is usually absent, but a soft murmur of either TR or a soft continuous murmur of PDA may be audible.
3. Inadequate interatrial communication causes hepatomegaly.
Electrocardiography
1. The QRS axis is normal (i.e., +60 to +140 degrees) in contrast to the superiorly oriented QRS axis seen in tricuspid atresia.
2. LVH is usually present. Occasionally, RVH is seen in infants with a relatively large RV cavity. RAH is common, occurring in 70% of cases.
Radiography
The heart size may be normal or large, resulting from RA enlargement. Pulmonary vascular markings are decreased with dark lung fields. The main PA segment is concave.
Echocardiography
1. Diagnostic features of the condition include (a) a thickened, immobile, atretic pulmonary valve with no Doppler evidence of blood flow through it; (b) a hypertrophied RV wall with a small cavity; (c) a patent, but small, tricuspid valve; (d) a right-to-left atrial shunt through an ASD demonstrated by color flow and Doppler studies; (e) and ductus arteriosus running vertically from the aortic arch to the PA (i.e., “vertical ductus”) (see Fig. 14-25).
2. The size of the tricuspid valve should be carefully measured because this measurement correlates well with the size of the RV cavity and thus determines whether a biventricular or univentricular repair is suitable (see Table D-5, Appendix D, for tricuspid and other valve annulus dimensions in the neonates). The most severely stenotic tricuspid valve is associated with the most underdeveloped RV and with likelihood of RV-dependent coronary circulation.
3. Images of the proximal coronary arteries help detect coronary artery anomalies. A coronary AV fistula is not easy to detect, but dilated or tortuous proximal coronary arteries suggest an RV-dependent coronary circulation. Color Doppler flow mapping may show retrograde flow in a proximal coronary artery. Absence of normal origin of a coronary artery may also suggest the presence of a fistulous connection to that coronary artery.
4. The right and left PA branches are usually well developed.
Cardiac Catheterization
Cardiac catheterization and angiocardiography are required for proper management in most patients with pulmonary atresia. A right ventriculogram demonstrates the size of the RV cavity and the presence or absence of coronary sinusoids (Fig. 14-44). An ascending aortogram identifies stenosis or interruption of the coronary arteries. Both are important in surgical decision making, whether to go for univentricular or biventricular repair.
FIGURE 14-44 Right ventriculograms in a patient with pulmonary atresia. A, Contrast medium filling the right ventricle (rv) passes into the ventricle-coronary fistula (sinus) and left anterior descending (LAD) coronary artery. Small white arrows point to multiple stenotic areas in the LAD. B, Massive filling of a dilated and irregular LAD coronary artery from the right ventricular injection (RV). (From Williams WG, Burrows P, Freedom RM, et al: Thromboexclusion of the right ventricle in children with pulmonary atresia and intact ventricular septum. J Thorac Cardiovasc Surg 101:222–229, 1991.)
Natural History
Without appropriate management (which includes PGE1 infusion and surgery), the prognosis is exceedingly poor. About 50% of these patients die by the end of the first month if not managed properly; about 80% die by 6 months of age. Death usually coincides with the spontaneous closure of the ductus arteriosus.
Management
Medical
1. PGE1 (Prostin VR Pediatric solution) infusion should begin as soon as the diagnosis is suspected or confirmed, so that the patency of the ductus arteriosus is maintained. Infusion is continued during cardiac catheterization and surgery. The starting dose of Prostin is 0.05 to 0.1 μg/kg per minute. When the desired effect is achieved, the dosage is gradually reduced to 0.01 μg/kg per minute.
2. For small premature infants, a prolonged course of PGE1 infusion may be necessary before surgery is undertaken.
3. In neonates with monopartite RV, who are not likely to be candidates for two-ventricular repair and are likely to require bidirectional Glenn operation or hemi-Fontan in a few months, some centers advocate using PDA stenting instead of the BT shunt. PDA stenting is less reliable and shorter lasting than the BT shunt but is likely to last to the time of bidirectional Glenn or hemi-Fontan procedure (Feltes et al, 2011).
4. A balloon atrial septostomy may be performed as part of the cardiac catheterization to improve the right-to-left atrial shunt, but it is recommended only when a two-ventricular repair is considered not possible (e.g., the presence of RV sinusoids or too small an RV cavity).
5. In patients with membranous atresia, a laser-assisted pulmonary valvotomy with balloon pulmonary valvuloplasty may be a useful alternative to a surgical procedure that establishes an RV-to-PA continuity (Cheung et al, 2002). Infundibular atresia is unsuitable for catheter intervention.
Surgical
The size of the RV (or that of the tricuspid valve) and the presence or absence of coronary sinusoids or coronary artery anomalies dictate surgical procedures for infants with pulmonary atresia with intact ventricular septum. Surgical options are as follows.
1. Two-ventricular repair, which is the ultimate goal whenever feasible, is possible only when there is an adequate size of the RV cavity with adequate RVOTs.
2. One and one-half ventricular repair may be chosen when the RV size is judged to be borderline for a two-ventricular repair but too good to be abandoned for Fontan-type repair.
3. One-ventricular repair (Fontan operation) is used when (a) an RV-dependent coronary circulation is present or (b) a monopartite RV (with a tricuspid valve z score <−4 to −5) is present.
4. Cardiac transplantation is a possible option.
Procedures
1. Staged two-ventricular repair: For the two-ventricular repair, the initial procedure consists of establishing a connection between the RV and the PA (to promote growth of the RV) and a systemic-to-PA shunt created at the same time. The second-stage operation consists of reconstruction of the RVOT.
a. First-stage operation: One of the following is done.
(1) Placement of a transannular RV outflow patch and a systemic-to-PA shunt seems most promising for a two-ventricular repair at a later date (Fig. 14-45). Balloon atrial septostomy is not recommended with this approach, so that a high RA pressure is maintained to maximize the forward RV output. The mortality rate is about 20%.
(2) For a patient with a well-formed pulmonary valve and adequate infundibulum, a closed transpulmonary valvotomy (without cardiopulmonary bypass) and a left-sided modified BT shunt procedure are performed. The mortality rate of these procedures is less than 5%.
(3) An alternative to the closed surgical valvotomy is the use of laser wire and radiofrequency-assisted valvotomy and balloon dilatation during cardiac catheterization (Cheung et al, 2002). The mortality rate of the procedure is about 5%.
b. Follow-up: After one of the above first-stage procedures, the growth of the RV is monitored in the following manner.
(1) Echocardiographic studies showing growth of the tricuspid valve size (to larger than z score >−2), evidence of growth of the RV size, and stable O2 saturation are positive signs for future two-ventricular repair.
(2) Cardiac catheterization is performed within 6 to 18 months after the initial surgery. An arterial O2 saturation greater than 70%, a greater RV volume, and evidence of a good forward flow through the pulmonary valve are all positive signs.
(3) If the patient tolerates balloon occlusion of the shunt during cardiac catheterization, the patient is considered a candidate for a two-ventricular repair.
c. The second-stage operation: RVOT reconstruction and closure of the ASD are carried out under cardiopulmonary bypass. The systemic-to-PA shunt is closed at the time of surgery. The mortality rate is about 15%.
2. One and one-half ventricular repair: This may be performed when the RV size is not quite large enough to have two-ventricular repair but the RV is too good to be abandoned for one-ventricular repair. This type of repair consists of the following.
a. A bidirectional Glenn anastomosis is created to bring the SVC blood directly to the pulmonary artery, bypassing the RV.
b. The IVC blood goes to the lungs via the normal pathway through the RV which is large enough to handle half of the systemic venous return.
FIGURE 14-45 Initial surgery for tripartite or bipartite type of pulmonary atresia. A, A longitudinal incision is made across the pulmonary annulus. The pulmonary valve is incised, and the right ventricular outflow tract is carefully widened. B, A piece of pericardium is used for the transannular patch. A left-sided Gore-Tex shunt is made between the left subclavian artery and the left pulmonary artery (PA). AO, aorta; LV, left ventricle; RA, right atrium; RV, right ventricle.
After this procedure, the size of the tricuspid valve and the RV may actually increase with an adequate RV function. Complications associated with Fontan procedure (e.g., arrhythmias, protein-losing enteropathy) do not occur after this procedure. The surgical mortality rate is between 0% and 12% (similar to Fontan).
3. One-ventricular repair (Fontan operation): For patients with monopartite RV (with or without coronary sinusoids), a two-ventricular repair is not possible. These patients need one-ventricular repair (Fontan operation).
a. A systemic-to-PA shunt without the RV outflow patch is recommended as the initial procedure. Some institutions use PDA stenting, instead of the BT shunt until the time of bidirectional Glenn or hermi-Fontan operation (at 3–6 months of age).
b. A staged Fontan operation is performed at a later time (see Tricuspid Atresia for a full description of the Fontan operation).
c. For patients who have rudimentary RV (with high RV pressure) and sinusoidal channels, there are two options.
(1) The sinusoids are left alone without decompression, and a systemic-to-PA shunt is performed for a future Fontan-type operation. Decompression of the RV by valvotomy or an outflow patch cannot be done because it results in a reversal of coronary flow into the RV, thereby producing myocardial ischemia.
(2) Alternatively, the tricuspid valve is closed (converting it to tricuspid atresia, the Starnes procedure) and a systemic-to-PA shunt is created for a future Fontan operation.
4. When the proximal portion of the coronary arteries is not identified or severe anomalies of the coronary circulation are present, cardiac transplantation may be an option.
The surgical approach to pulmonary atresia with intact ventricular septum is illustrated in Figure 14-46.
FIGURE 14-46 Surgical approach to pulmonary atresia with intact ventricular septum. BDG, bidirectional Glenn; BT, Blalock-Taussig; op, operation; RV, right ventricle; RVOT, right ventricular outflow tract; RV-PA conn, right ventricle–to–pulmonary artery connection.
Postoperative Follow-up
Most patients require close follow-up because none of the surgical procedures available is curative.
Hypoplastic Left Heart Syndrome
Prevalence
Hypoplastic left heart syndrome occurs in 1 in 5000 live births. About 2000 infants are born annually with the defect in the United States. About 10% of cases are associated with genetic syndromes such as Turner syndrome, trisomy 18, Jacobsen’s syndrome, and others.
Pathology
1. HLHS includes a group of closely related anomalies characterized by hypoplasia of the LV, atresia or critical stenosis of the aortic or mitral valves, and hypoplasia of the ascending aorta and aortic arch. The LV is small and nonfunctional or totally atretic.
2. The atrial septum may be intact with a normal foramen ovale, or the patient may have a true ASD (15%). A VSD appears in about 10% of patients. COA frequently is an associated finding (up to 75%).
3. A high prevalence of brain abnormalities has been reported. Up to 29% of the patients had a CNS abnormality. Overt CNS malformations (e.g., agenesis of the corpus callosum, holoprosencephaly) were seen in 10% of these infants. Micrencephaly was found in 27% of the infants, and an immature cortical mantle was seen in 21% of the patients. The presence or absence of dysmorphic physical features did not predict CNS malformations (Glauser et al, 1990).
Pathophysiology
1. During fetal life, the PVR is higher than the SVR, and the dominant RV maintains normal perfusing pressure in the descending aorta and the placenta through the ductal right-to-left shunt. The proximal aorta and the coronary and cerebral circulations are adequately perfused retrogradely. Fetuses tolerate this serious cardiac anomaly well in utero.
2. Difficulties arise after birth for two reasons: reduction of PVR (with the onset of respiration) and closure of the ductus arteriosus. The result is a marked reduction in the aortic perfusing pressure and systemic hypoperfusion, producing circulatory shock and metabolic acidosis.
3. Maintenance of adequate systemic blood flow (and thus survival of these infants) depends on an adequate size of the ductus arteriosus and maintenance of a high PVR to permit the RV to send an adequate amount of blood flow to the aorta. Large pulmonary blood flow increases pulmonary venous return to the LA. An adequate interatrial communication is necessary to decompress the LA. In the presence of a large ASD that permits a left-to-RA shunt, pulmonary edema is not severe, and the arterial oxygen saturation may be in the 80s. With an inadequate atrial septal communication, pulmonary edema is severe, and the arterial oxygen saturation is low. Without treatment, the infant usually dies shortly after birth.
Clinical Manifestations
1. A neonate with HLHS becomes critically ill within the first few hours to the first few days of life. Tachycardia, dyspnea, pulmonary crackles, weak peripheral pulses, and vasoconstricted extremities are characteristic. The patient may not have severe cyanosis but has a grayish blue color of the skin with poor perfusion.
2. The S2 is loud and single. Heart murmur usually is absent. Occasionally, a grade 1 to 2 of 6 nonspecific ejection systolic murmur may be heard over the precordium. Signs of CHF develop, with hepatomegaly and gallop rhythm.
3. The ECG almost always shows RVH. Rarely, the ECG suggests LVH with large R waves in V5 and V6 (because these leads are placed over the dilated RV, not over the hypoplastic LV).
FIGURE 14-47 Anteroposterior view of chest film (A) and lateral view of an aortogram (B) in a 1-day-old newborn with HLHS. The heart is enlarged, and the pulmonary vascularity is increased, with marked pulmonary venous congestion and pulmonary edema (A). The aortogram, obtained with injection of a radiopaque dye through an umbilical artery catheter, shows a hypoplastic ascending aorta (thick arrows) with small coronary arteries (thin arrows) filling retrogradely, a large patent ductus arteriosus (PDA), and pulmonary artery (PA) branches.
4. Chest radiography characteristically shows pulmonary venous congestion or pulmonary edema (Fig. 14-47, A). The heart is moderately or markedly enlarged.
5. Arterial blood gas levels reveal a slightly decreased Po2 and a normal Pco2. Severe metabolic acidosis out of proportion to the Pco2 (caused by markedly decreased cardiac output) is characteristic of the condition.
6. Echocardiographic findings are diagnostic and usually obviate the need for cardiac catheterization and angiocardiography.
a. The LV cavity is diminutive, but the RV cavity is markedly dilated, and the tricuspid valve is large.
b. Imaging usually reveals severe hypoplasia of the aorta and aortic annulus and an absent or distorted mitral valve. COA frequently is an associated anomaly.
c. The patient may have an ASD or a PFO with a left-to-right shunt. The patient occasionally has a VSD with a relatively large LV, aortic annulus, and ascending aorta.
d. Color-flow mapping and Doppler studies reveal retrograde blood flow in the aortic arch and ascending aorta (to perfuse the head and the coronary circulation).
Natural History
Pulmonary edema and CHF develop in the first week of life. Circulatory shock and progressive hypoxemia and acidosis result in death, usually in the first month of life.
Management
Presurgical Medical Management
1. The patient should be intubated and ventilated appropriately with oxygen, and metabolic acidosis is corrected.
2. IV infusion of PGE1 (Prostin VR Pediatric) may temporarily improve HLHS by reopening the ductus arteriosus (for the dosage, see Appendix E).
3. Balloon atrial septostomy may help decompress the LA and improve oxygenation but produces only a temporary benefit.
4. Support therapy only without surgical procedure is no longer acceptable in most parts of the world.
5. Infants with HLHS should have careful genetic, ophthalmologic, and neurologic evaluations, including imaging of their intracranial anatomy, and long-term follow-up because of a high prevalence of neurodevelopmental abnormalities seen with the condition.
Surgical
Three options are available in the management of these infants: (1) the Norwood operation (followed by a Fontan-type operation), (2) a hybrid operation (followed by a Fontan-type operation), and (3) cardiac transplantation. The surgical procedure of choice remains controversial, but the Norwood operation is more popular than cardiac transplantation. A hybrid operation is being done in increasing numbers, but its long-term advantages are not clear at this time. A rare subgroup of patients with normal-sized LV (because of a large VSD) can have a two-ventricular repair rather than the Fontan operation.
FIGURE 14-48 Schematic diagram of the Norwood procedure. A, The heart with aortic atresia with a hypoplastic ascending aorta and aortic arch, along with a large pulmonary artery (PA) and ductus arteriosus, are shown. The main PA is transected. B, An incision that extends around the aortic arch to the level of the ductus is made in the ascending aorta. The distal PA is closed with a patch. The ductus arteriosus is ligated and divided. C, A modified right Blalock-Taussig shunt is created between the right subclavian artery and the right PA (RPA) as the sole source of pulmonary blood flow. Alternatively, a homograft conduit may be placed between the right ventricle (RV) and PA bifurcation as shown in the figure (Sano modification). Note that only one of these two procedures is performed but not both. By the use of an aortic or PA allograft (striped area), the main PA is anastomosed to the ascending aorta and the aortic arch to create a large new arterial trunk. The Norwood procedure also includes widening of the atrial communication which is not shown in the illustration. LPA, left pulmonary artery; RA, right atrium.
Staged Surgical Approach
1. The first-stage (Norwood) operation is performed initially and followed later by the Fontan-type operation.
a. The Norwood operation is performed in the neonatal period. The operation consists of the following procedures (Fig. 14-48).
(1) The main PA is divided, the distal stump is closed with a patch, and the ductus arteriosus is ligated.
(2) Using an aortic or PA allograft, one connects the proximal PA and the hypoplastic ascending aorta and aortic arch.
(3) Pulmonary blood flow is established by one of the following procedures.
(a) A right-side modified BT shunt is created (using a 4- to 5-mm Gore-Tex tube) to provide pulmonary blood flow while preventing CHF and pulmonary hypertension.
(b) An RV-to-PA shunt (using polytetrafluorethylene graft) was first used by Sano and colleagues (4 mm for patients weighing <2 kg and 5 mm for those weighing >2 kg) (Sano modification).
The Sano central shunt may be an advantage over the modified BT shunt for the following reasons. Although the central shunt requires a right ventriculotomy to complete the shunt, (1) it promotes symmetrical growth of the pulmonary arteries, and (2) it provides a higher aortic diastolic pressure and thus a higher coronary artery perfusion pressure than the BT shunt does. The BT shunt, on the other hand, provides continuous forward flow to the PA during both systole and diastole, causing diastolic retrograde flow in the central aorta, which may cause “coronary steal” during diastole.
(4) The atrial septum is excised to allow adequate interatrial mixing.
b. The Norwood procedure carries the highest surgical mortality rate among common cyanotic CHD, ranging from 7% to 19%. In addition, between the Norwood operation and the second-stage operation, 4% to 15% of infants die. A recent report shows that survival rate after the first-stage (Norwood) operation was significantly higher in infants who had a Sano modification than those who had a modified BT shunt (74% vs. 64%) (Ohye et al, 2010).
c. Post-Norwood medical management. Most patients are placed on the following medications after the Norwood operation (and most of them are continued throughout their lives even after the final Fontan operation).
(1) Small-dose diuretic therapy (not to produce hypovolemia).
(2) Digoxin is given by some centers.
(3) Captopril, an afterload-reducing agent, is given (to increase systemic blood flow, thereby possibly to reduce pulmonary blood flow).
(4) Aspirin is given to prevent shunt thrombosis.
(5) Nutritional support is very important, if necessary, including nasogastric feeding or a gastrostomy tube feeding.
2. Second-stage operation for HLHS is either the bidirectional Glenn procedure or the hemi-Fontan procedure. These procedures are performed at 3 to 6 months of age.
a. Cavopulmonary shunt (also called the bidirectional Glenn operation) is an end-to-side anastomosis of the SVC to the right PA (see Fig. 14-38, A) performed at 3 to 6 months of age in an effort to reduce the volume overload to the systemic RV. The mortality rate for this procedure is less than 5%.
b. The hemi-Fontan operation. This procedure includes augmentation of the central PA without dividing the SVC while excluding IVC blood from the pulmonary arteries by means of a temporary intraatrial patch (see Fig. 14-39).
3. A modified Fontan operation is performed at 1 to 2 years of age (see Fig. 14-38, B). Five important hemodynamic and anatomic features considered essential to successful Fontan operation include (1) unrestrictive interatrial communication, (2) competence of the tricuspid valve, (3) unobstructed PA-to-descending aorta anastomosis (with pressure gradient <25 mm Hg), (4) undistorted PAs and low PVR, and (5) preservation of RV function.
Currently, the operative mortality rate of the Fontan procedure is less than 3%. Patients with HLHS have a higher likelihood of prolonged pleural effusion and hospital stay than those with tricuspid atresia. Mean PA pressure of 15 mm Hg or greater was associated with prolonged hospital stay and unfavorable outcomes (Rogers et al, 2012). Significant TR appears to be an important predictor of poor outcome of the Fontan operation. The overall survival rate after the Fontan operation is better than 95% at follow-up of 50 months (Hirsch et al, 2008).
Hybrid Approach
A hybrid approach followed later by the Fontan-type operation was first reported in 2008 (Galantowicz et al, 2008). Many centers now use this procedure as an alternative to the Norwood (stage I) procedure for high-risk HLHS and single-ventricle patients or as a bridge to heart transplantation in infants with HLHS.
The advantages of this approach are that (1) it creates a stable, balanced circulation without the use of open heart surgery using cardiopulmonary bypass, which carries a relatively high risk, and (2) it delays the open heart procedure until later in life when a bidirectional Glenn or hemi-Fontan operation can be safely performed (3–6 months of age).
a. A hybrid procedure is performed in the first weeks of life. The procedure consists of (1) bilateral PA banding through a small median sternotomy using a 1- to 2-mm ring from a 3.5-mm Gore-Tex tube graft (3.0-mm tube for patients <2.5 kg) to provide adequate pulmonary blood flow but without causing pulmonary hypertension or heart failure and (2) insertion of a PDA stent in the same setting through a sheath placed (through purse string) in the main PA to ensure adequate systemic and coronary perfusion (see Fig. 14-49). The surgical mortality rate is 2.5%, which is much lower than that for the Norwood operation (7%–19%). As a separate procedure, atrial septostomy with or without balloon dilatation is performed to establish a reliable atrial shunt.
b. Comprehensive stage 2 surgery is performed at 3 to 6 months of age with a surgical mortality rate of 8%. The second-stage procedures combine the Norwood operation and bidirectional Glenn operation. Thus, the stage 2 procedures include (1) removal of PDA stent and PA bands, (2) repair of aortic arch and the pulmonary arteries (especially the LPA if necessary), (3) reimplantation of the diminutive ascending aorta into the pulmonary root, (4) atrial septostomy, and (5) bidirectional Glenn operation.
FIGURE 14-49 Hybrid stage I intervention for hypoplastic left heart syndrome. Surgical bands around the right and left pulmonary arteries limit blood flow to the lungs, and a stent in the ductus arteriosus holds it open and maintains adequate blood flow to the body. A balloon atrial septostomy allows unobstructed return of pulmonary venous blood to the heart. LA, left atrium; LPA, left pulmonary artery; RA, right atrium; RPA, right pulmonary artery.
c. A Fontan-type operation is performed at the age of 2 years, the same as that described under the staged Norwood approach.
Other Surgical Approaches
1. Infants with aortic atresia and normal-sized LV caused by a large VSD can have a biventricular repair, rather than a Fontan approach. The VSD is tunneled to the PA. The main pulmonary artery (MPA) is divided, and the proximal MPA is connected to the ascending aorta. The RV is connected to the distal MPA using a valved conduit or a homograft.
2. Some centers considered cardiac transplantation the procedure of choice in the past. If the diameter of the ascending aorta is smaller than 2.5 mm, cardiac transplantation, rather than the Norwood operation, was believed to provide a better result. The surgical technique of cardiac transplantation is presented in Chapter 35.
For patients placed on a transplantation algorithm, it is necessary to keep the ductus open and to increase the size of the interatrial communication. A hybrid procedure may be used as a bridge to cardiac transplantation, in which an endovascular stent is placed in closing ductus to keep the ductus open and PA branches are banded to control pulmonary blood flow. Blade atrial septostomy followed by balloon dilatation has been performed for decompression of the LA.
At this time, not all cardiac centers offer orthotropic heart transplantation. The availability of the donor heart is limited, and the overall mortality rate while awaiting transplantation is 21% to 37%. Furthermore, this approach requires lifelong immunosuppression with the attendant risks of rejection, infection, graft atherosclerosis, and malignancies. Some patients may require subsequent retransplantation caused by allograft vasculopathy and graft dysfunction.
Postsurgical Follow-up Plan
After the second-stage operation and the final Fontal operation, the follow-up plans are similar to those described for tricuspid atresia (also refer to Box 14-2).
Figure 14-50 summarizes surgical approaches used in the management of patients with HLHS.
FIGURE 14-50 Surgery for hypoplastic left heart syndrome. BDG, bidirectional Glenn; BT, Blalock-Taussig; PA pulmonary artery; PDA, patent ductus arteriosus.
FIGURE 14-51 Diagram of Ebstein’s anomaly of the tricuspid valve. There is an apicalward displacement of the tricuspid valve, usually the septal and posterior leaflets, into the right ventricle (RV). Part of the RV is incorporated into the right atrium (RA) (“atrialized” portion of the RV). Regurgitation of the tricuspid valve results in RA enlargement. An atrial septal defect (ASD) is usually present. CS, coronary sinus; IVC, inferior vena cava; LPA, left pulmonary artery; PA, pulmonary artery; RPA, right pulmonary artery; SVC, superior vena cava.
Ebstein’s Anomaly
Prevalence
Ebstein’s anomaly of the tricuspid valve occurs in less than 1% of all CHDs.
Pathology
1. There is downward displacement of the septal and posterior leaflets of the tricuspid valve into the RV cavity, so that a portion of the RV is incorporated into the RA (i.e., atrialized RV), and functional hypoplasia of the RV results (Fig. 14-51). Tricuspid regurgitation is usually present, and redundant tricuspid valve tissues can rarely obstruct the RVOT, which results in dilatation and hypertrophy of the RA.
2. An interatrial communication (e.g., PFO, true ASD) with a right-to-left shunt is present in all patients.
3. The RV free wall is often dilated and thin. Fibrosis is present in both RV and LV free walls; this may be responsible for severe symptoms early in life and LV dysfunction in later life.
4. WPW preexcitation is frequently associated with the anomaly and predisposes the patient to SVT.
5. PS, pulmonary atresia, TOF, VSD, and other defects are occasionally associated with the anomaly.
Clinical Manifestations
History
1. In severe cases, cyanosis and CHF develop during the first few days of life. Some subsequent improvement coincides with reduction of the PVR.
FIGURE 14-52 Cardiac findings of Ebstein’s anomaly. Quadruple rhythm and a soft, regurgitant systolic murmur (of tricuspid regurgitation) are characteristic of the defect.
FIGURE 14-53 Tracing from a 5-year-old child with Ebstein’s anomaly. The tracing shows right atrial hypertrophy, right bundle branch block, and first-degree atrioventricular block.
2. Children with milder cases may complain of dyspnea, fatigue, cyanosis, or palpitation on exertion.
3. A history of SVT is occasionally present.
Physical Examination
1. Mild to severe cyanosis is present, as well as clubbing of the fingers and toes in older infants and children.
2. Characteristic triple or quadruple rhythm is audible. This rhythm consists of a widely split S2, split S1, S3, and S4. A soft holosystolic (or early systolic) murmur of TR is usually audible at the lower left sternal border (Fig. 14-52). A soft, scratchy, mid-diastolic murmur is present at the same location.
3. Hepatomegaly is usually present.
Electrocardiography
1. Characteristic ECG findings of RBBB and RAH are present in most patients with this condition (Fig. 14-53).
2. First-degree AV block is frequent, occurring in 40% of patients. A WPW pattern of preexcitation is present in 15% to 20% of patients (with occasional episodes of SVT).
Radiography
In mild cases, the heart is almost normal in size and has normal pulmonary vascular markings. In severe cases, an extreme cardiomegaly (principally involving the RA) with a balloon-shaped heart and decreased pulmonary vascular markings is present. Some of the largest heart sizes are found in newborns with this condition (Fig. 14-54).
Echocardiography
Two-dimensional echocardiography with color-flow Doppler study is the procedure of choice for the diagnosis and functional assessment of Ebstein’s anomaly; cardiac catheterization and angiography are not needed.
1. The single most diagnostic feature is apical displacement of the hinge point of the septal leaflet of the tricuspid valve (Fig. 14-55). Normally, the septal leaflet of the tricuspid valve inserts on the ventricular septum slightly below the insertion of the mitral valve. In patients with Ebstein’s anomaly, this normal displacement is exaggerated. A diagnosis of Ebstein’s anomaly is made when the tricuspid valve is displaced toward the apex by more than 8 mm/m2 of BSA from the mitral valve insertion. This displacement is best seen in the apical four-chamber view.
FIGURE 14-54 Posteroanterior view (A) and diagram (B) of chest roentgenogram from a 2-week-old infant with severe Ebstein’s anomaly. Note extreme cardiomegaly involving primarily the right atrium (RA) and diminished pulmonary vascularity. Ao, aorta; ARV, atrialized right ventricle; LV, left ventricle; PA, pulmonary artery; RV, right ventricle.
FIGURE 14-55 Echocardiogram (A) and diagram (B) of an apical four-chamber view in a patient with Ebstein’s anomaly. The septal leaflet is displaced into the right ventricle (RV; large dark arrow) and thus forms an atrialized RV (aRV). The anterior tricuspid leaflet is elongated. Both leaflets are tethered to underlying myocardium (small arrows). The tricuspid annulus and the right atrium (RA) are dilated. AS, atrial septum; fRV, functional right ventricle; LA, left atrium; LV, left ventricle; mv, mitral valve; tv, tricuspid valve; VS, ventricular septum. (From Shiina A, Serwer JB, Edwards WD, et al: Two-dimensional echocardiographic spectrum of Ebstein’s anomaly: Detailed anatomic assessment. J Am Coll Cardiol 3:356–370, 1984.)
2. The tricuspid valve leaflets are elongated, redundant, and dysplastic with abnormal chordal attachment.
3. A large RA, including the atrialized RV, and a small functional RV represent anatomic severity. Evidence of tricuspid valve regurgitation and tricuspid stenosis (TS) is present.
4. RVOT obstruction may occur owing to the redundant anterior leaflet of the tricuspid valve.
5. A nonrestrictive ASD is commonly imaged.
6. Other anomalies may include mitral valve prolapse and LV dysfunction.
Other Studies. Cardiac catheterization is rarely necessary in patients with Ebstein’s anomaly. In patients who had a BT shunt, it may be indicated to exclude distortion of the PA or pulmonary hypertension before planning cavopulmonary shunts and Fontan-type operations.
Natural History
1. Some 18% of symptomatic newborns die in the neonatal period; 30% of patients die before the age of 10 years, usually from CHF.
2. Cyanosis tends to improve as the PVR falls during the newborn period. Cyanosis may reappear later.
3. Patients with a less severe anomaly may be either asymptomatic or mildly symptomatic.
4. Hemodynamic deterioration with increasing cyanosis, CHF, and LV dysfunction develops later in life. These developments foretell early death.
5. Attacks of SVT with associated WPW preexcitation occur in 15% to 20% of all patients. Sudden, unexpected death can occur, probably as a result of arrhythmias.
6. Other possible complications include infective endocarditis, brain abscess, and cerebrovascular accident.
Management
Medical
1. In severely cyanotic newborns, intensive treatment with mechanical ventilation, PGE1 infusion, inotropic agents, and correction of metabolic acidosis may be necessary before proceeding with emergency surgery.
2. In infants who appear to have a mild form of Ebstein’s anomaly and to be improving with the above management, treatment with PGE1 and inotropic support is gradually withdrawn to observe the effect of ductal closure.
3. Asymptomatic children with mild Ebstein’s anomaly require only regular observation. If CHF develops, anticongestive measures, including digoxin and diuretics, are indicated.
4. Acute episodes of SVT may be treated most effectively with adenosine (see Chapter 24). Beta-blockers are the most appropriate first-line preventive therapy for SVT. For patients with recurrent SVT caused by AV reentrant mechanism, radiofrequency catheter ablation techniques have been successful.
5. Varying degrees of activity restriction may be necessary for children with this condition.
Surgical
Indications
Although surgical indications for Ebstein’s anomaly are not completely defined, they may include the following:
1. Critically ill neonates who show symptoms within the first week of life (after a period of intensive medical treatment)
2. Occurrence of moderately severe or progressive cyanosis (arterial saturation of ≤80%), polycythemia (hemoglobin level of ≥16 g/dL), or CHF
3. RVOT obstruction by redundant tricuspid valve
4. Severe activity limitation (i.e., NYHA functional class III or IV) (see Appendix A, Table A-3)
5. History of paradoxical embolus
6. Repeated, life-threatening arrhythmias in patients with associated WPW syndrome
Procedures
Controversy exists concerning the types and timing of surgical procedures.
1. Palliative procedures. For critically ill neonates, if medical management does not show signs of improvement, surgical intervention is indicated to avoid certain death.
a. BT shunt (with enlargement of ASD). This procedure can be lifesaving when there are obstructive lesions between the RV and the PA or stenotic tricuspid valve. Good LV function (with adequate LV size) is required to survive the procedure. A Fontan-type operation is performed later (see Fig. 14-38).
b. If the LV is “pancaked” by large RV or RA, a procedure to reduce the RV or RA may be considered, such as the Starnes operation (pericardial closure of the tricuspid valve) or plication of large RA (atrialized RV), enlargement of ASD, and a BT shunt using a 4-mm tube. A Fontan-type operation (see Fig. 14-38) is performed later.
c. Classic Glenn anastomosis (SVC to right PA end-to-end anastomosis) or its modification may be considered in severely cyanotic infants.
FIGURE 14-56 Danielson technique for tricuspid valve repair. A, A series of interrupted mattress sutures are placed to obliterate the atrialized portion of the right ventricle (RV). The atrial septal defect (ASD) is closed with a patch. B, As the sutures are tied, the atrialized portion of the RV is obliterated (seen through a right atriotomy). C, Sutures are placed to further narrow the tricuspid orifice. The valve is now a monocusp valve (anterior leaflet of the tricuspid valve) that is mobile and opens widely during diastole. AO, aorta; PA, pulmonary artery; RA, right atrium.
2. Definitive procedures. Children with good RV size and function are candidates for biventricular repair (with tricuspid valve repair or replacement). An inadequate RV size or function requires Fontan operation.
a. Two-ventricular repair: Reconstruction of the tricuspid valve (e.g., Danielson and Carpentier procedure) is preferable to valve replacement. ASD is closed at the time of surgery.
(1) Danielson technique: For repair of the tricuspid valve, this technique is the most desirable and best tested, although it is frequently limited by anatomy. This technique can be applied in about 60% of patients (Fig. 14-56). It plicates the atrialized portion of the RV, narrows the tricuspid orifice in a selective manner, and results in a monoleaflet valve (by the anterior leaflet of the tricuspid valve). Two other leaflets are often severely hypoplastic and cannot be made to function as a leaflet. The mortality rate is about 5%, which is lower than that for valve replacement.
(2) Carpentier technique: As an alternative, Carpentier reconstructive surgery may be used. This repair also plicates the atrialized portion of the RV and the tricuspid annulus but in a direction that is at right angles to those used by Danielson. This repair can be applied in most patients with Ebstein’s anomaly. The surgical mortality rate is 15%.
(3) Tricuspid valve replacement and closure of the ASD are a less desirable surgical approach but may be necessary for 20% to 30% of patients with Ebstein’s anomaly who are not candidates for reconstructive surgery. The replacement valve of choice is a stented, antibiotically treated semilunar valve allograft or a heterograft valve. A pulmonary allograft valve mounted in a short Dacron sleeve can be used in younger children. The surgical mortality rate ranges from 5% to 20%.
b. One-ventricular repair: For patients with inadequate size of the RV, a Fontan-type operation is usually performed in stages following the initial palliative procedures such as a bidirectional Glenn operation or hemi-Fontan operation (see Fig. 14-38).
3. Other procedures. For patients with WPW syndrome and recurrent SVT, surgical interruption at the time of surgery or radiofrequency ablation of the accessory pathway is recommended.
Complications
1. Complete heart block is a rare complication.
2. Supraventricular arrhythmias persist in 10% to 20% of patients after surgery.
Postoperative Follow-up
1. Frequent follow-up is necessary because of the persistence of arrhythmias after surgery, which occurs in 10% to 20% of patients, and because of possible problems associated with tricuspid valve surgery that require reoperation.
2. The patient should not participate in competitive or strenuous sports.
FIGURE 14-57 Surgical approaches for Ebstein’s anomaly of the tricuspid valve. ASD, atrial septal defect; BDG, bidirectional Glenn; BT, Blalock-Taussig; LV, left ventricle; RA, right atrium; RV, right ventricle; RVOT, right ventricular outflow tract; TV, tricuspid valve.
FIGURE 14-58 The anatomic type of persistent truncus arteriosus (TA) is determined by the branching patterns of the pulmonary arteries. A, In type I, the main pulmonary artery (PA) arises from the truncus and then divides into the right (RPA) and left pulmonary artery (LPA) branches. B, In type II, the RPA and LPA arise separately from the posterior aspect of the truncus. C, In type III, the PAs arise separately from the lateral aspects of the truncus. D, In type IV, or pseudotruncus arteriosus, arteries arising from the descending aorta (AO) supply the lungs. LA, left atrium; LV, left ventricle; RA, right atrium; RV, right ventricle.
Surgical approaches for Ebstein’s anomaly are shown in Figure 14-57.
Persistent Truncus Arteriosus
Prevalence
Persistent truncus arteriosus occurs in fewer than 1% of all CHDs.
Pathology
1. Only a single arterial trunk with a truncal valve leaves the heart and gives rise to the pulmonary, systemic, and coronary circulations. A large perimembranous, infundibular VSD is present directly below the truncus (Fig. 14-58). The truncal valve may be bicuspid, tricuspid, or quadricuspid, and it is often incompetent.
2. According to Collett and Edwards’ classification, this anomaly is divided into four types by how the pulmonary arteries arise from the truncus arteriosus (see Fig. 14-58 for the description of each type). Types I and II constitute 85% of cases. Type IV is not a true persistent truncus arteriosus; rather, it is a severe form of TOF with pulmonary atresia (i.e., pseudo-truncus arteriosus), with aortic collaterals supplying the lungs.
3. The pulmonary blood flow is increased in type I, nearly normal in types II and III, and decreased in type IV.
4. Coronary artery abnormalities are common and may contribute to the high surgical mortality rate. The anomalies include stenotic coronary ostia, high and low takeoff of coronary arteries, and abnormal branching and course of the coronary arteries.
5. Interrupted aortic arch is seen in 13% of cases (this is type A4 of van Praagh classification). In this case, the interruption occurs distal to the takeoff of the left carotid artery and lower extremity flow is accomplished through the PDA.
6. A right aortic arch is present in 30% of patients.
7. Evidence of DiGeorge syndrome with hypocalcemia is present in 33% of patients.
Clinical Manifestations
History
1. Cyanosis may be seen immediately after birth.
2. Signs of CHF develop within several days to weeks after birth.
3. A history of dyspnea with feeding, failure to thrive, and frequent respiratory infections is usually present in infancy.
Physical Examination
1. Varying degrees of cyanosis and signs of CHF with tachypnea and dyspnea are usually present.
2. The peripheral pulses are bounding, with a wide pulse pressure. The precordium is hyperactive, and the apical impulse is displaced laterally.
3. A systolic click is frequently audible at the apex and upper left sternal border. The S2 is single. A harsh (grade 2 to 4 of 6), regurgitant systolic murmur, which suggests VSD, is usually audible along the left sternal border. An apical diastolic rumble with or without gallop rhythm may be present when the PBF is large. A high-pitched, early diastolic, decrescendo murmur of truncal valve regurgitation may be audible.
Electrocardiography
The QRS axis is normal (+50 to +120 degrees). BVH is present in 70% of cases; RVH or LVH is less common. Left atrial hypertrophy (LAH) is occasionally present.
Radiography
Cardiomegaly is usually present, with increased pulmonary vascularity. A right aortic arch is seen in 30% of cases.
Echocardiography
Two-dimensional and Doppler echocardiography show the following. The first three findings are diagnostic.
1. A large VSD is imaged directly under the truncal valve, similar to that seen in TOF.
2. A large, single great artery arises from the heart (i.e., truncus arteriosus). The type of persistent truncus arteriosus can be identified, and the size of the PAs can be determined. An artery, branching posteriorly from the truncus, is the PA.
3. The pulmonary valve cannot be imaged; only one semilunar valve (i.e., truncal valve) is imaged.
4. Cross-sectional imaging may determine the number of sinuses (usually three, although it may be two or four) of the truncal valve and the presence or absence of stenosis or regurgitation of the valve.
5. Right aortic arch is frequently present (in ≈35%). Interruption of the aortic arch is occasionally present, which is difficult to image.
Other Studies
Preoperative cardiac catheterization is now rarely necessary in neonates. However, with late diagnosis of the condition, cardiac catheterization may be performed to evaluate PA pressure and PVR.
Natural History
1. Most infants present with CHF during the first 2 weeks. A total of 85% of untreated children die by 1 year of age.
2. Clinical improvement occurs if the infant develops pulmonary vascular obstructive disease, which may begin to occur by 3 to 4 months of age. Death occurs around the third decade of life.
3. Truncal valve insufficiency worsens with time.
Management
Medical
1. Vigorous anticongestive measures with diuretics and ACE inhibitors should be pursued before an operation is undertaken.
2. Because of the frequent association of DiGeorge syndrome:
a. Serum calcium and magnesium levels should be checked; supplementation may be indicated.
b. Only irradiated blood product should be used for an urgent surgery (because of an insufficient time for evaluation of immune status accurately).
c. Because of the thymus-based immune deficiency, treatment and prophylaxis against pneumococcal and streptococcal infections are important.
d. Immunization with live vaccine should be avoided.
3. Prophylaxis against SBE should be observed when indications arise.
Surgical
Palliative Procedures
Although PA banding was performed in the past in small infants with large PBF and CHF, primary repair of the defect is currently recommended by many centers. The banding produces distortion of the PAs and does not necessarily prevent pulmonary vascular obstructive disease. The procedure is associated with a high mortality rate, as high as 30%.
Definitive Procedure
1. Various modifications of the Rastelli procedure are performed. Ideally, surgery should be undertaken within the first week of life. When the diagnosis is delayed, surgery should be performed on an urgent basis after 2 to 3 days of medical stabilization.
2. For all types, the VSD is closed in such a way that the LV ejects into the truncus. The surgical mortality rate is 10% to 30%. Careful investigation of coronary artery anomalies and avoidance of surgical interruption of the coronary arteries are important.
a. For type I, an aortic homograft (with internal diameter of 9–11 mm) is placed between the RV and the PA (Fig. 14-59).
b. For types II and III, a circumferential band of the truncus, which contains both PA orifices, is removed. This cuff is tailored and then connected to the RV by the use of a homograft. Aortic continuity is restored with a tubular Dacron graft (Fig. 14-60).
c. When associated with an interrupted aortic arch, aortic reconstruction is done by anastomosis of the proximal and distal aortas. The RPA is brought anterior to the ascending aorta (Lecompte maneuver) to prevent compression on the RPA. Using a homograft, the RV and the PA are connected.
3. The regurgitant truncal valve is almost always amenable to various repair techniques. A prolapsing vestigial leaflet can be supported by suturing to the adjacent leaflet (closure of a commissure). Truncal valve replacement is indicated if there is significant truncal valve insufficiency. It has an extremely high mortality rate of 50% or greater.
FIGURE 14-59 Operative technique for type I truncus arteriosus. A, Truncus arteriosus type I is shown with a large ventricular septal defect (VSD; broken circle) directly under the truncal valve. The vertical broken line on the right ventricle (RV) is the site of the right ventriculotomy. B,The pulmonary artery (PA) trunk has been cut away from the truncal artery, and the opening in the truncal artery is sutured. Patch closure of the VSD (which is visible through the ventriculotomy) is completed in such a way that only left ventricular blood goes out to the truncal artery (creating the left ventricle [LV]–to–truncal artery pathway). C, A valved conduit or homograft is anastomosed to the pulmonary trunk. The posterior half of the proximal conduit is anastomosed to the upper end of the ventriculotomy. A small pericardial patch is trimmed and sutured into place to fill the defect between the allograft and the lower end of the right ventriculotomy. AO, aorta; RA, right atrium.
FIGURE 14-60 Operative technique for types II and III truncus arteriosus. A, Two broken lines on the truncal artery indicate the sites of excision of the pulmonary arteries (PAs). The vertical broken line is the site of the right ventriculotomy. A ventricular septal defect (VSD) is under the truncal valve (broken circle). B, The VSD is closed with a patch through a right ventriculotomy (which is visible through the ventriculotomy) in such a way that the truncal artery receives blood only from the left ventricle (LV) (LV-to-truncus pathway). The cuff of truncal tissue, including the PA orifices, has been excised and trimmed. C, Continuity of the truncal artery, which is now the aorta (AO), has been restored with a Dacron graft. The lower end of a homograft has been anastomosed to the right ventriculotomy, and the upper end of the homograft has been anastomosed to the cuff containing the PAs. RA, right atrium; RV, right ventricle.
Postoperative Follow-up
1. Follow-up every 4 to 12 months is required to detect late complications, either natural or postoperative.
a. Progressive truncal valve insufficiency may develop, and truncal valve repair or replacement may be needed.
b. A small conduit needs to be changed to a larger size, usually by 2 to 3 years of age.
c. Calcification of the valve in the conduit may occur within 1 to 5 years, which requires reoperation.
d. Ventricular arrhythmias may develop because of right ventriculotomy.
2. Balloon dilatation and stent implantation in the RV-to-PA conduit can prolong conduit longevity and delay the need to surgically replace the conduit.
3. For older children who had received a larger sized conduit and develop valvular regurgitation after balloon dilatation of the conduit valve, a nonsurgical percutaneous pulmonary valve implantation technique has been developed by Bonhoeffer et al (2000), and this technique has been used successfully in Europe (see further discussion under TOF with pulmonary atresia in this chapter).
FIGURE 14-61 Diagram of the most common form of single ventricle. The single ventricle is an anatomic left ventricle (double-inlet LV). The great arteries are transposed (L-transposition), with the aorta (AO) anterior to and left of the pulmonary artery (PA) and arising from the rudimentary right ventricle (RV). Both atrioventricular valves open into the single ventricle (double-inlet LV). The opening between the main and rudimentary ventricles is the bulboventricular foramen (thick arrow). Stenosis of the pulmonary valve is present in about 50% of cases (shown as thick valves). This type accounts for 70% to 75% of cases of single ventricle. LA, left atrium; MV, mitral valve; RA, right atrium; TV, tricuspid valve.
4. SBE prophylaxis should be observed throughout life.
5. The patient should not participate in strenuous competitive sports.
Single Ventricle
Prevalence
Single ventricle (double-inlet ventricle) occurs in fewer than 1% of all CHDs.
Pathology
1. Both AV valves are connected to a main, single ventricular chamber (i.e., double-inlet ventricle), and the main chamber is in turn connected to a rudimentary chamber through the BVF. One great artery arises from the main chamber, and the other arises from the rudimentary chamber (Fig. 14-61). In about 80% of cases, the main ventricular chamber has anatomic characteristics of the LV (i.e., double-inlet LV). Occasionally, the main chamber has anatomic characteristics of the RV (i.e., double-inlet RV). Rarely does the ventricle have an intermediate trabecular pattern without a rudimentary chamber (i.e., common ventricle). Also, both atria rarely empty via a common AV valve into the main ventricular chamber with either LV or RV morphology (i.e., common-inlet ventricle).
2. Either D-TGA or L-TGA is present in 85% of cases. The most common form of single ventricle is double-inlet LV with L-TGA with the aorta arising from the rudimentary chamber. This type occurs in 70% to 75% of single ventricle (see Fig. 14-61). The mitral valve is right sided; the tricuspid valve is left sided. PS or pulmonary atresia is present in about 50% of cases. COA and interrupted aortic arch are also common. Less commonly, D-TGA is present with the aorta arising from the right and anterior rudimentary chamber.
3. The BVF is frequently obstructive.
4. Anomalies of the AV valves are common, which include stenosis, overriding, or straddling.
5. In double-inlet RV, either right or LA isomerism and straddling or overriding of the AV valves is common.
Pathophysiology
1. Because there is a complete mixing in the single ventricle, the systemic arterial saturation is determined primarily by the amount of PBF.
a. With PS, PBF is decreased, and cyanosis is present (with arterial oxygen saturation <85%). With pulmonary atresia, cyanosis is intense at birth.
b. When the pulmonary valve is not stenotic, the PBF is large, and signs of CHF develop within days or weeks without cyanosis; arterial oxygen saturation is nearly 90%.
2. An obstructed BVF may either occur naturally with growth or, for unknown reasons, develop after PA banding. This condition occurs in 70% to 85% of patients who receive PA banding. The occurrence of an obstructed foramen has a profound hemodynamic effect, as well as major surgical implications in patients with the aorta arising from the anterior rudimentary chamber. The obstruction increases PBF and decreases systemic perfusion. The banding also causes excessive hypertrophy of the main ventricle (LV), resulting in decreased compliance of the ventricle, which places the patient at risk for a future Fontan operation.
Clinical Manifestations
History
1. Cyanosis of varying degrees may be present from birth.
2. History of failure to thrive or pneumonia may be present in infants with increased pulmonary blood flow (signs of CHF).
Physical Examination
Physical findings depend on the magnitude of PBF.
1. With increased PBF, physical findings resemble those of TGA plus VSD or even those of large VSD:
a. Mild cyanosis and CHF with growth retardation are present in early infancy.
b. The S2 is single or narrowly split with a loud P2. A grade 3 to 4 of 6 long systolic murmur is audible along the left sternal border. An apical diastolic rumble may be audible. A diastolic murmur of PR may be present along the upper left sternal border as a result of pulmonary hypertension.
2. With decreased PBF, physical findings resemble those of TOF.
a. Moderate to severe cyanosis is present. CHF is not present. Clubbing may be seen in older infants and children.
b. The S2 is loud and single. A grade 2 to 4 of 6 ejection systolic murmur may be heard at the upper right or left sternal border.
Electrocardiography
1. An unusual ventricular hypertrophy pattern with similar QRS complexes across most or all precordial leads is common (e.g., RS, rS, or QR pattern).
2. Abnormal Q waves (representing abnormalities in septal depolarization) are also common and take one of the following forms: Q waves in the right precordial leads, no Q waves in any precordial leads, or Q waves in both the right and left precordial leads.
3. Either first- or second-degree AV block may be present.
4. Arrhythmias such as SVT or wandering pacemaker may occur.
Radiography
1. With increased PBF, the heart size enlarges and the pulmonary vascularity increases.
2. When PBF is normal or decreased, the heart size is normal and the pulmonary vascularity is normal or decreased.
3. A narrow upper mediastinum suggests TGA.
Echocardiography
1. The most important diagnostic sign of single ventricle is the presence of a single ventricular chamber into which two AV valves open.
2. The following anatomic and functional information is important from a surgical point of view. Efforts should be made to obtain information on all of these aspects in each patient with single ventricle:
a. Morphology of the single ventricle (e.g., double-inlet LV? double-inlet RV?).
b. Location of the rudimentary outflow chamber, which is usually left and anterior.
c. Size of the BVF and whether there is an obstruction at the foramen. Obstruction of the foramen is considered present if the Doppler gradient is more than 1.5 m/sec or if the area of the foramen is less than 2 cm2/m2. A foramen that is nearly as large as the aortic annulus is considered ideal.
d. Presence or absence of D-TGA or L-TGA, stenosis of the pulmonary or aortic valve, and size of the PAs.
e. Anatomy of the AV valves. The position of the mitral and tricuspid valves, in addition to the presence of stenosis, regurgitation, hypoplasia, or straddling of these valves, should be checked.
f. The size of the ASD.
g. Associated defects such as COA, interrupted aortic arch, or PDA.
Other Studies
Echocardiographic and Doppler studies provide most of the anatomic and hemodynamic information needed for the initial management of single ventricle. Cardiac catheterization is performed only when certain preoperative information is not available before the initial stage of surgical management. It is, however, routinely indicated before stages II and III surgical intervention.
Natural History
1. In patients without PS, CHF and growth failure develop in early infancy in association with pulmonary hypertension. Without surgery, about 50% of these patients die before reaching 1 year of age. The remainder of the patients with increased PBF develop pulmonary vascular obstructive disease after the first year of life with clinical improvement of CHF.
2. In patients with associated PS, cyanosis increases if PS worsens.
3. If the aorta arises from the rudimentary chamber, the BVF is often small or becomes obstructed. This results in increased PBF and decreased systemic perfusion.
4. Progressive AV valve regurgitation is poorly tolerated.
5. Complete heart block develops in about 12% of patients.
6. The cause of death can be CHF, arrhythmias, or sudden death.
Management
Initial Medical Management
1. Newborns with severe PS or pulmonary atresia and those with interrupted aortic arch or coarctation require PGE1 infusion and other supportive measures before surgery.
2. Anticongestive measures are indicated if CHF develops.
Surgical
1. Initial surgical palliative procedures
a. The purpose of the first-stage operation is to make patients acceptable candidates for bidirectional Glenn or hemi-Fontan operation. Cyanosis with oxygen saturation less than 85% or increased pulmonary blood flow with possible future pulmonary hypertension is an indication for the operation. The presence or absence of PS or of obstructive BVF results in one of the following four situations. PS (or pulmonary atresia) is present in about 50% of the patients. When there is no PS, pulmonary overcirculation can lead to pulmonary hypertension, which jeopardizes future Fontan operation.
(1) In patients with no PS and large PBF with resulting CHF and pulmonary edema, PA banding may be done, although the banding carries a high mortality rate (≈25% or even higher). The major risk factor for the banding is the presence or development of an obstructed BVF. Most infants with an obstructed foramen do not tolerate the banding well. Therefore, PA banding is performed, only when the BVF is normal or unobstructed. In addition, these patients should be watched for the development of obstruction after the banding.
(2) In patients with no PS, if the BVF is too small, the Damus-Kaye-Stansel operation is performed rather than the PA banding. The operation involves a PA-to-aorta anastomosis, which is accomplished by transection of the main PA and anastomosis of the proximal PA to the ascending aorta. This operation is combined with a right-sided BT shunt (Fig. 14-62) or a single ventricle–to–the main PA (Sano) shunt (not shown). A Fontan-type operation can be performed later (see Fig. 14-38, B).
FIGURE 14-62 Damus-Kaye-Stansel anastomosis for single ventricle and subpulmonary stenosis. A, The pulmonary artery (PA) is transected proximal to the bifurcation. An appropriately positioned and sized incision is made in the ascending aorta (AO). B, The distal end of the PA is oversewn, and the proximal end of the PA is anastomosed to the opening in the aorta. C, An appropriately shaped hood (Dacron tube, pericardium, allograft, or Gore-Tex) is added to the anastomosis. A Blalock-Taussig shunt has been completed. Sano shunt can be placed instead (not shown here). LV, left ventricle; RA, right atrium; RV, right ventricle.
(3) If PS or pulmonary atresia is present (with O2 saturation <85%), a BT shunt is necessary to improve cyanosis. Shunt to the right PA is preferable because any distortion of the RPA can be incorporated later in the Fontan anastomosis. The mortality rate is low (5%–10%). In PGE1-dependent neonates, the PDA is ligated after placement of the shunt.
Recently, a hybrid procedure consisting of PDA stenting, bilateral PA banding, and balloon atrial septostomy (with or without balloon dilatation), as discussed under HLHS, has been used as an alternative to the BT shunt.
(4) If PS is present and the BVF is obstructive, enlargement of the BVF by a transaortic approach and without cardiopulmonary bypass may be performed. The surgical mortality rate is about 15%. An additional BT shunt may be needed to provide adequate pulmonary blood flow.
b. Surgery for interrupted aortic arch or coarctation should be performed, if present.
c. After the first-stage operation, the infant should be watched closely, until the time of the second-stage palliation, for cyanosis (with O2 saturation <75%) or signs of CHF (too large a pulmonary blood flow for which tightening of the PA band should be considered).
2. Second-stage surgical palliative procedures
a. A bidirectional Glenn operation (see Fig. 14-38) is carried out between the age of 3 and 6 months, before proceeding with the Fontan operation. Alternatively, a hemi-Fontan procedure can be performed (see Fig. 14-39).
b. After the second-stage surgical procedure, the child needs to be followed up with attention to the O2 saturation. The follow-up plans are the same as those described in Box 14-2.
3. Definitive (Fontan) procedures
The Fontan-type operation is performed at 18 to 24 months of age. Many centers consider the lateral tunnel Fontan procedure the procedure of choice (see Figs. 14-38, B, and 14-40). Some centers make a 4- to 6-mm fenestration in the baffle, and others do not. Some centers prefer the extracardiac conduit modification of the Fontan procedure, which may reduce the incidence of late atrial arrhythmias. If an AV valve is incompetent, it may need to be closed during surgery. The surgical mortality rate of the Fontan-type operation has been reduced to 5% to 10%, similar to that for tricuspid atresia.
The surgical approaches in single ventricle are summarized in Fig. 14-63.
FIGURE 14-63 Surgical approach for single ventricle. BDG, bidirectional Glenn; BVF, bulboventricular foramen; BT, Blalock-Taussig; CHF, congestive heart failure; PBF, pulmonary blood flow; PS, pulmonary stenosis; RPA, right pulmonary artery.
Postoperative Follow-up
1. Close follow-up is necessary for early and late complications, which have been discussed in detail under tricuspid atresia.
2. Some survivors of surgery, if performed late, remain symptomatic with cyanosis, dyspnea as a result of ventricular dysfunction, and arrhythmias. These symptoms require regular follow-up. Early surgery as outlined above tends to reduce unfavorable results.
Double-Outlet Right Ventricle
Prevalence
Double-outlet right ventricle (DORV) occurs in fewer than 1% of all CHDs. DORV occurs frequently in patients with heterotaxy in association with other complex cardiac defects.
Pathology
1. Both the aorta and the PA arise from the RV. The only outlet from the LV is a large VSD.
2. The great arteries usually lie side by side. The aorta is usually to the right of the PA, although one of the great arteries may be more anterior than the other. The aortic and pulmonary valves are at the same level. Conus septum is present between the aorta and the PA. The subaortic and subpulmonary coni separate the aortic and pulmonary valves from the tricuspid and mitral valves, respectively. This means that there is no fibrous continuity between the semilunar valves and the AV valves. In a normal heart, the aortic valve is lower than the pulmonary valve, and the aortic valve is in fibrous continuity with the mitral valve.
3. The position of the VSD and the presence or absence of PS (or RVOT obstruction) influence hemodynamic alterations and form the basis for dividing the defect into the following types of DORV (Fig. 14-64):
a. Subaortic VSD. The VSD is closer to the aortic valve than to the pulmonary valve and lies to the right of the conus septum (see Fig. 14-64, A). This is the most common type, occurring in 55% to 70% of cases.
b. Fallot type. In about 50% of patients with subaortic VSD, RVOT obstruction occurs (Fig. 14-64, B). RVOT obstruction is most commonly caused by infundibular stenosis, but rarely pure valvular PS can occur with small annulus.
c. Subpulmonary VSD (i.e., Taussig-Bing anomaly) (see Fig. 14-64, C). The VSD is closer to the pulmonary valve than to the aortic valve, and it usually lies above the crista supraventricularis and to the left of the conus septum. This type accounts for approximately 10% to 30% of cases.
FIGURE 14-64 Diagram of three representative types of double outlet right ventricle, viewed with the free wall of the right ventricle (RV) removed. A, Subaortic ventricular septal defect (VSD). B, Subaortic VSD with pulmonary stenosis (Fallot type). C, Subpulmonary VSD (Taussig-Bing anomaly). Open arrows represent highly oxygenated blood, and black arrows represent desaturated blood. Doubly committed and remote VSDs are not shown. AO, aorta; CS, crista supraventricularis; PA, pulmonary artery; RA, right atrium; RV, right ventricle.
d. Doubly committed VSD. The VSD is closely related to both semilunar valves and is usually above the crista supraventricularis (<5% of cases).
e. Noncommitted (or remote) VSD. The VSD is clearly away from the semilunar valves (≈10% of cases). It most commonly represents the AV canal-type VSD and occasionally an isolated muscular VSD. Atrial isomerism is commonly seen with this type.
4. Sometimes surgeons’ and pathologists’ definitions of DORV are different and are the source of confusion. Some cases of TOF with marked overriding of the aorta may be called DORV by surgeons because the mitral–aortic fibrous continuity is not always clear in the operating room. Surgeons use the so-called 50% rule: when the aortic annulus overlies the RV by at least 50%, it is called DORV.
Pathophysiology and Clinical Manifestations
The pathophysiology and clinical manifestations of DORV are determined primarily by the position of the VSD and the presence or absence of PS. Each type is presented separately.
1. Subaortic VSD without PS. In subaortic VSD, oxygenated blood from the LV is directed to the aorta, and desaturated systemic venous blood is directed to the PA, thereby producing mild or no cyanosis (see Fig. 14-64, A). The PBF increases in the absence of PS, and CHF may result. Therefore, the clinical pictures of this type resemble those of a large VSD with pulmonary hypertension and CHF.
a. Growth retardation, tachypnea, and other signs of CHF are usually present. A hyperactive precordium, a loud S2, and a VSD-type (holosystolic or early systolic) murmur are present. An apical diastolic rumble may be audible.
b. The ECG often resembles that of complete endocardial cushion defect (ECD). “Superior” QRS axis (i.e., −30 to −170 degrees) may be found in this type. RVH or BVH, as well as LAH, is common. Occasionally, first-degree AV block is present.
c. Chest radiography shows cardiomegaly with increased pulmonary vascular markings and a prominent PA segment.
2. Subaortic VSD with PS (Fallot type). Even though the VSD is subaortic, in the presence of PS (or RVOT obstruction), some desaturated blood goes to the aorta. This causes cyanosis and a decrease in PBF. The clinical pictures resemble those of TOF (see Fig. 14-64, B).
a. Growth retardation and cyanosis are common. The S2 is loud and single. A grade 2 to 4 of 6 midsystolic (ejection) murmur along the left sternal border is present, either with or without a systolic thrill.
b. The ECG shows RAD, RAH, RVH, or RBBB. First-degree AV block is frequent.
c. Chest radiography shows normal heart size with an upturned apex. Pulmonary vascularity is decreased.
3. Subpulmonary VSD (Taussig-Bing malformation). In subpulmonary VSD, or Taussig-Bing malformation, oxygenated blood from the LV is directed to the PA, and desaturated blood from the systemic vein is directed to the aorta. This results in severe cyanosis (see Fig. 14-64, C). The PBF increases with the fall of the PVR. Clinical pictures resemble those of complete TGA.
a. Growth retardation and severe cyanosis with or without clubbing are common findings. The S2 is loud, and a grade 2 to 3 of 6 systolic murmur is audible at the upper left sternal border. An ejection click and an occasional PR murmur (as a result of pulmonary hypertension) may be audible.
b. The ECG shows RAD, RAH, and RVH. LVH may be seen during infancy.
c. Chest radiography shows cardiomegaly with increased pulmonary vascular markings and a prominent PA segment.
4. Doubly committed or noncommitted VSD. With the VSD close to both semilunar valves (called doubly committed VSD) or remotely located from these valves (noncommitted VSD), cyanosis of a mild degree is present, and the PBF increases.
Echocardiography
Three diagnostic signs of DORV are the origin of both great arteries from the anterior RV, the absence of LV outflow other than the VSD, and the discontinuity of the mitral and semilunar valves.
1. In the parasternal long-axis view, all three diagnostic features of DORV are imaged. Typical subaortic or subpulmonary VSD can be demonstrated in this view for most patients (Fig. 14-65). No great artery is seen to arise from the posterior ventricle. The great arteries arising from the anterior ventricle are seen in parallel orientation. In addition, a mass of echocardiography-positive tissue, usually larger than 5 mm in length, is present between the mitral valve annulus and the semilunar valve (i.e., mitral–semilunar discontinuity).
2. In the parasternal short-axis view, a double circle, rather than the normal circle and sausage appearance of the great arteries, may be seen. Either the great arteries are side by side with the aorta to the right or the aorta is anterior and slightly to the right of the PA.
3. The size and position of the VSD should be determined in relation to the great arteries.
a. Typical subpulmonary or subaortic VSD can be demonstrated by parasternal long-axis scanning in most patients (see Fig. 14-65).
b. In the subcostal four-chamber view, the subaortic VSD is located to the right of the conus septum just beneath the aortic valve. The subpulmonary VSD is located to the left of the conus septum just beneath the pulmonary valve.
FIGURE 14-65 Parasternal long-axis view of double outlet right ventricle. A, Subaortic ventricular septal defect (VSD). The VSD is closely related to the aorta (AO). The marked separation between the anterior mitral valve leaflet and the aortic valve can be seen. The aorta overrides the ventricular septum by more than 50%. B, Subpulmonary VSD. The great artery that is closely related to the VSD has an immediate posterior sweep, suggesting that it is a pulmonary artery (PA). Note the separation between the anterior mitral leaflet and the pulmonary valve. The PA overrides the ventricular septum by more than 50%. LA, left atrium; LV, left ventricle; RV, right ventricle. (A from Snider AR, Serwer GA: Echocardiography in Pediatric Heart Disease, St. Louis, Mosby, 1990; B from Snider AR: Two-dimensional and Doppler echocardiographic evaluation of heart disease in the neonate and fetus. Clin Perinatol 15:523–565, 1988.)
c. Doubly committed VSD is recognized in the parasternal or the apical long-axis view.
d. Noncommitted (remote) VSDs, either endocardial cushion type or apical muscular VSD, are best recognized in the apical four-chamber view.
4. Associated anomalies such as valvular or subvalvular PS and other left-to-right shunt lesions (e.g., ASD, PDA) should be looked for.
5. Occasionally, differentiation of DORV from TOF with a marked overriding of the aorta or from TGA is necessary. There is mitral–semilunar continuity in TOF and TGA (i.e., mitral–aortic continuity in TOF and mitral–pulmonary continuity in TGA), but no mitral–semilunar continuity is present in DORV.
Other Studies
Cardiac catheterization and angiocardiography are not necessary for initial surgical management of the condition with PA banding or BT shunt. They are indicated to perform atrial septostomy in patients with Taussig-Bing malformation with inadequate atrial septal mixing. They are usually indicated before later stage operations.
Natural History
1. Infants without PS may develop severe CHF and later pulmonary vascular obstructive disease if left untreated. Spontaneous closure of VSD, which is fatal, is rare.
2. When PS is present, complications common to cyanotic CHDs (e.g., polycythemia, cerebrovascular accident) may develop.
3. In patients with the Taussig-Bing malformation, severe pulmonary vascular obstructive disease develops early in life, as seen in patients with D-TGA.
4. Associated anomalies (e.g., COA, LV hypoplasia) also contribute to the poor prognosis.
Management
Medical
Treatment of CHF with diuretics, ACE inhibitors, and digoxin is indicated.
Surgical
Palliative Procedures
1. PA banding for symptomatic infants with increased PBF and CHF is occasionally performed in infants with multiple muscular VSD or a remote VSD. However, this procedure is not recommended for infants with subaortic VSD or doubly committed VSD. Primary repair is a better choice.
2. For infants with the Taussig-Bing type, enlarging the interatrial communication is important for better mixing and for decompressing the LA, which causes pulmonary venous congestion. Balloon or blade atrial septostomy should be considered.
3. In infants with PS and decreased PBF with cyanosis, a systemic-to-PA shunt procedure is occasionally indicated.
Definitive Surgeries
1. Subaortic or doubly committed VSD. An intraventricular tunnel between the VSD and the subaortic outflow tract is created by means of a Dacron patch. This procedure is performed early in life, preferably during the neonatal period or at least in early infancy, without preliminary PA banding. Sometimes the RVOT may have to be augmented with an outflow patch if the VSD–AO tunnel obstructs the RV outflow tract. The mortality rate is less than 5% for simple subaortic VSD; it is slightly higher for doubly committed VSD.
2. Fallot type. There are three surgical options. Surgical repair is generally advised by 6 months of age, preferably during the neonatal period. However, if the patient’s condition is poor or if there are major associated noncardiac anomalies, an initial shunt operation is an option.
a. Tunnel VSD closure + Rastelli operation. An intraventricular tunnel between the VSD and the aorta is established, and a Rastelli operation is performed to relieve PS using either a pulmonary or aortic homograft conduit.
b. REV procedure. So-called reparation a l’etage ventriculare (REV), which is similar to ASO, may be performed. In the REV procedure, the proximal ascending aorta and main PA are transected, and the proximal stump of the PA is oversewn (see Fig. 14-9, which is performed for D-TGA + VSD + PS, a situation very similar to this one). The pulmonary arteries are translocated anterior to the aorta (Lecompte maneuver), and the ascending aorta is reconnected. The distal PA is anastomosed directly to the upper margin of the infundibular incision. Autologous pericardium forms the anterior portion of the pathway. The hospital mortality rate is 18%.
c. Nikaidoh procedure. This combines the principle of the Ross procedure and the Konno operation. The aortic root including the aortic valve is detached in the same manner as done to the pulmonary root in the Ross procedure. The PA is divided, and the pulmonary valve is excised. The pulmonary root is divided, and the conal septum above the VSD is excised, which creates a large opening to the LV cavity. The aortic root is translocated posteriorly and sutured to the open orifice of the pulmonary annulus. A pericardial patch is used to connect the lower margin of the VSD and the anterior circumference of the harvested aortic root, completing the LV to AO connection. A pericardial gusset completes the connection of the RV and the distal end of the MPA (see Fig. 14-10, which has been described for D-TGA + VSD + PS).
3. Taussig-Bing anomaly (subpulmonary VSD). There are four possible surgical approaches. These operations should be carried out by 3 to 4 months of age or sooner because of the rapid development of pulmonary vascular obstructive disease in this subtype.
a. The procedure of choice is the creation of an intraventricular tunnel between the VSD and the PA (resulting in TGA), which is then corrected by the ASO. The mortality rate is between 5% and 15%.
b. Creation of an intraventricular tunnel between the VSD and the PA is followed by the Senning operation. This is a less desirable approach because of a high mortality rate (>40%) and a higher late complication rate associated with the Senning procedure.
c. An intraventricular tunnel between the VSD and the aorta is desirable but often technically impossible. The surgical mortality rate is about 15%.
d. Creation of a VSD-to-PA tunnel followed by the Damus-Kaye-Stansel operation and RV–to-PA conduit is another possibility.
4. Noncommited VSD. When possible, an intraventricular tunnel procedure between the AV canal-type VSD and the aorta is performed, but the mortality rate is high (30%–40%). PA banding is usually needed in infancy to control CHF, and the surgery may be delayed until 2 to 3 years of age.
The surgical approach for patients with DORV is summarized in Figure 14-66.
Postoperative Follow-up
Long-term, regular follow-up at 6- to 12-month intervals is necessary to detect and manage late complications of surgery.
1. In general, patients who had subaortic VSD without PS have an excellent long-term outlook.
2. Ventricular arrhythmia should be treated because it may cause sudden death.
3. About 20% of patients require reoperation of the intraventricular tunnel.
Heterotaxia (Atrial Isomerism, Splenic Syndromes)
There is a failure of differentiation into right- and left-sided organs in heterotaxia (splenic syndrome or atrial isomerism), with resulting congenital malformations of multiple organs systems, including complex malformation of the cardiovascular system. Asplenia syndrome (Ivemark’s syndrome, RA isomerism) is associated with absence of the spleen, which is a left-sided organ, and a tendency for bilateral right-sidedness. In polysplenia syndrome (LA isomerism), multiple splenic tissues are present, with a tendency for bilateral left-sidedness.
FIGURE 14-66 Surgical approach for DORV. AO, aorta; ASD, atrial septal defect; ASO, arterial switch operation; BT, Blalock-Taussig; PA, pulmonary artery; REV, réparation à I܀étage ventriculare; RV, right ventricle; RVOT, right ventricular outflow tract; RV-PA, RV–to–pulmonary artery; VSD, ventricular septal defect; VSD-AO, VSD-to-aorta; VSD-PA, VSD–to–pulmonary artery.
There is a striking tendency for symmetrical development of normally asymmetrical organs or pairs of organs. Members of paired organs, such as the lungs, commonly show pronounced isomerism; unpaired organs, such as the stomach, seem to be located in a random fashion. Table 14-2 compares cardiovascular abnormalities in asplenia and polysplenia syndromes. Although the types and severity of cardiovascular malformations differ as a group between the two syndromes, the same types of defects are present in both. The abnormalities that help differentiate the two are shown with asterisks, but probably the most significant differential power is the IVC, which is almost always normal with asplenia syndrome but is interrupted (with azygous continuation) with polysplenia. In general cardiovascular abnormalities are much more severe in patients with asplenia than in those with polysplenia.
Some noncardiac findings suggest heterotaxia. Because of the symmetry of paired organs, normally different right- and left-sided organs show the same morphology. Some clinical findings available to general physicians that may lead to the recognition of heterotaxia include the following.
1. Symmetric “midline” liver (on palpation or radiography)
2. Discordant cardiac apex and stomach bubble (on chest radiography)
3. Biliary atresia in a neonate with CHDs
4. Symmetric mainstem bronchi on chest radiography
5. Superior P axis (or coronary sinus rhythm) on the ECG
It is important to know which type of isomerism one has from the point of prophylaxis against bacterial infection, asplenia or polysplenia syndrome. Patients with asplenia syndrome are prone to fulminating sepsis and should be given daily antibiotic prophylaxis and vaccinated against pneumococcus, Haemophilus influenzae type b (Hib), and meningococcus (see below).
Asplenia Syndrome
Prevalence
Asplenia syndrome occurs in 1% of newborns with symptomatic CHDs. This syndrome occurs more often in boys than girls.
TABLE 14-2
CARDIOVASCULAR MALFORMATIONS IN ASPLENIA AND POLYSPLENIA SYNDROMES
|
Structure |
Asplenia Syndrome |
Polysplenia Syndrome |
|
Systemic veins |
Bilateral SVC (65%); single SVC usually right (35%) |
Bilateral SVC (33%); single SVC right or left (66%) |
|
Normal IVC in all but may be left-sided (35%) |
∗Interrupted IVC (absent hepatic segment of IVC) with azygos continuation right or left (85%) |
|
|
†IVC and aorta on the same side, either right or left |
Juxtaposition of IVC and aorta occasionally |
|
|
Normal hepatic veins to IVC (75%) |
Bilateral, common hepatic vein to RA or LA |
|
|
Pulmonary veins |
∗TAPVR with extracardiac connection: supracardiac or infracardiac (>80%), often with PV obstruction |
†Normal PV return (50%) |
|
Coronary sinus |
Absent coronary sinus (most) |
Absent coronary sinus (most) |
|
Atrium and atrial septum |
Bilateral right atria (with bilateral sinus node) |
Bilateral, left atria |
|
†Absent atrial septum (common atrium) common; primum ASD (100%), secundum ASD (66%) |
Single (or common) atrium, primum ASD (60%), or secundum ASD (25%) |
|
|
AV valve |
∗Common (single) AV valve (90%) |
Normal AV valve (50%); single AV valve rare |
|
Ventricles and cardiac apex |
VSD always present |
VSD frequent but not always |
|
Left apex (60%); right apex (40%) |
Left apex (60%); right apex (40%) |
|
|
Semilunar valves |
†Stenosis (40%) or atresia (40%) of PV |
Normal PV (60%); PS or pulmonary atresia (40%) |
|
Great arteries |
∗Transposition (70%), either D- or L- |
†Normal great arteries (85%); transposition (15%) |
|
ECG |
Normal P axis or in the +90 to +180 degree quadrant |
†Superior P axis (70%) |
ASD, atrial septal defect; AV, atrioventricular; DORV, double-outlet right ventricle; IVC, inferior vena cava; PS, pulmonary stenosis; PV, pulmonary venous or vein; RA, right atrium; RV, right ventricle; SVC, superior vena cava; TAPVR, total anomalous pulmonary venous return; VSD, ventricular septal defect.
∗ Extremely important differentiating points.
† Important differentiating points.
Pathology
1. The spleen is absent in asplenia syndrome. A striking tendency for bilateral right-sidedness characterizes malformations of the major organ systems. Bilateral, three-lobed lungs with bilateral, eparterial bronchi (Fig. 14-67); various gastrointestinal malformations (occurring in 20% of cases); a symmetrical, midline liver; and malrotation of the intestines are all present. The stomach may be located on either the right or the left.
2. Complex cardiac malformations are always present. Cardiovascular malformations involve all parts of the heart, systemic and pulmonary veins, and great arteries. Two sinoatrial nodes are present. Table 14-2summarizes and compares these malformations with those of polysplenia syndrome. Cardiovascular anomalies that help distinguish asplenia syndrome from polysplenia syndrome include the following:
a. A normal IVC is present in asplenia syndrome, but the hepatic portion of the IVC is commonly absent (with azygous continuation draining into the SVC) in polysplenia syndrome.
FIGURE 14-67 Diagrams of normal bronchi (A); bilateral eparterial bronchi, usually seen in asplenia syndrome (B); and bilateral hyparterial bronchi, usually seen in polysplenia syndrome (C). (From Fyler DC, ed: Nadas’ Pediatric Cardiology, St. Louis, Mosby, 1992.)
b. TGA with PS or pulmonary atresia occurs in about 80% of asplenia syndrome cases, thereby producing severe cyanosis during the newborn period. TGA is present in only 15% of patients with polysplenia syndrome.
c. Single ventricle and common AV valve occur with greater frequency in asplenia syndrome. In polysplenia syndrome, two ventricles are usually present.
d. TAPVR to extracardiac structures occurs in more than 75% of cases of asplenia syndrome, although it is difficult to diagnose. Pulmonary venous return is normal in 50% of patients with polysplenia syndrome.
Pathophysiology
1. Complete mixing of systemic and pulmonary venous blood usually occurs because of the multiple cardiovascular abnormalities associated with this syndrome.
2. PBF is reduced because of stenosis or atresia of the pulmonary valve. This results in severe cyanosis shortly after birth.
3. Although rare, the absence of PS may result in CHF early in life.
Clinical Manifestations
Physical Examination
1. Cyanosis is usually the presenting sign and is often severe.
2. Auscultation of the heart is nonspecific. Heart murmurs of PS and VSD are frequently audible.
3. A symmetrical liver (midline liver) is palpable.
Electrocardiography
1. A “superior” QRS axis is present, as a result of the presence of ECD.
2. The P axis is either normal (0 to +90 degrees) or alternating between the lower left and lower right quadrants. This occurs because two sinus nodes alternate the pacemaker function.
3. RVH, LVH, or BVH is present.
Radiography
1. The heart size is usually normal or slightly increased, with decreased pulmonary vascular markings.
2. The heart is in the right chest, left chest, or midline (mesocardia).
3. A symmetrical liver is a striking feature (see Fig. 4-8).
4. Tracheobronchial symmetry with bilateral, eparterial bronchi is usually identified.
Echocardiography
When the systematic approach is used, two-dimensional echocardiography and color-flow Doppler studies can detect all or most of the anomalies described in the section on pathology. The anatomy of the IVC and great arteries and the presence or absence of PS or pulmonary atresia are important in differentiating the two splenic syndromes.
Other Imaging Modalities
Cardiac MRI or CT is usually indicated because almost all of the patients with asplenia syndromes have complex anomalies of pulmonary and systemic venous returns, which cannot be accurately imaged by echocardiographic studies.
Laboratory Studies
1. Howell-Jolly and Heinz bodies seen on the peripheral smear suggest asplenia syndrome. However, these bodies may be found in some normal newborns and in septic infants.
2. A splenic scan may be useful in older infants but is of limited value in extremely ill neonates.
Natural History
Without palliative surgical procedures, more than 95% of patients with asplenia syndrome die within the first year of life. Fulminating sepsis is one cause of death.
Management
Medical
1. In severely cyanotic newborns, PGE1 infusion is given to reopen the ductus. (If obstructive anomalous pulmonary venous return is suspected, pulmonary angiography should be obtained while the ductus is open by PGE1 infusion.)
2. The risk of fulminating infection, especially by Streptococcus pneumoniae, is high (Red Book, 2012). Continuous oral antibiotic therapy is recommended regardless of immunization status. Oral penicillin V (125 mg, twice a day for children younger than 5 years, and 250 mg, twice a day for children 5 years of age and older) is recommended. Some experts recommend amoxicillin (20 mg/kg per day, divided into two doses). Erythromycin (250 mg twice daily) is an alternate choice in patients who are allergic to penicillin. Prophylactic penicillin can be discontinued at 5 years of age, but some experts continue prophylactic penicillin throughout childhood and into adulthood.
3. Asplenic infants and children have a high risk of fulminant bacteremia, especially associated with encapsulated bacteria. Streptococcus pneumoniae is the most common pathogen that causes bacteremia in asplenic children. Less common causes of bacteremia include Hib, Neisseria meningitidis, and many others.
a. Pneumococcal conjugate and polysaccharide vaccines are indicated for all children with asplenia at the recommended age (Red Book, 2012). After administration of an appropriate number of doses of PCV13, pneumococcal polysaccharide vaccine (PPSV23) should be given starting at 24 months of age. A second dose should be administered 6 years later. For children 2 through 5 years of age with a complete PCV7 series who have not received PCV13, a supplemental dose of PCV13 should be administered. For asplenic people 6 through 18 years of age who have not received a dose of PCV13, a supplemental dose of PCV13 should be considered (Red Book, 2012).
b. Hib immunization should be initiated at 2 months of age, as recommended for otherwise healthy children.
c. Two primary doses of quadrivalent meningococcal conjugate vaccine should be administered 2 months apart to children 2 years through adolescence, and a booster dose should be given every 5 years, although its efficacy has not been established.
Surgical
1. A systemic-to-PA shunt is usually necessary during the newborn period or infancy. Surgical mortality for the shunt is higher in asplenia patients than in those with other defects, and it is probably related to regurgitation of the common AV valve and undiagnosed obstructive TAPVR.
a. Patients with a common AV valve, especially those with regurgitation of the valve, do not tolerate the volume overload that results from the shunt.
b. Patients with the obstructive type of TAPVR may show evidence of the anomalous return, with signs of pulmonary edema, only after the systemic-to-PA shunt. The surgical mortality rate for both the shunt and repair of the TAPVR is unacceptably high in that death occurs in more than 90% of cases.
c. Identification of infants with obstructive TAPVR by pulmonary angiography with PGE1 infusion before surgery is important. In infants with the infracardiac type of TAPVR, a successful connection can be made between the pulmonary venous confluence and the RA with the use of a partial exclusion clamp and without cardiopulmonary bypass.
2. A Fontan-type operation can be performed with the overall mortality rate as high as 65%. Regurgitation of the AV valve is a high-risk factor, requiring repair or replacement of the valve.
Polysplenia Syndrome
Prevalence
Polysplenia syndrome (LA isomerism) occurs in fewer than 1% of all CHDs. It occurs usually in females (70%).
Pathology
1. Multiple splenic tissues are present. A tendency for bilateral left-sidedness characterizes this syndrome. Noncardiovascular malformations include bilateral, bilobed lungs (i.e., two left lungs); bilateral, hyparterial bronchi (see Fig. 14-67); a symmetrical liver (25%); occasional absence of the gallbladder; and some degree of intestinal malrotation (80%).
2. Cardiovascular malformations are similar to those seen in asplenia syndrome but have a lower frequency of pulmonary valve stenosis or atresia. Occasionally, a normal heart or minimal malformation of the heart is present in patients with polysplenia syndrome (≈13%). Cardiovascular malformations are summarized and compared with those of asplenia syndrome in Table 14-2. Important features of polysplenia syndrome that distinguish it from asplenia syndrome include the following:
a. Absence of the hepatic segment of the IVC with azygous (right side) or hemiazygous (left side) continuation is seen in 85% of patients. This abnormality is rarely present in asplenia syndrome.
b. Two ventricles are usually present. On the contrary, single ventricle with a common AV valve is common in asplenia syndrome.
c. TGA, PS or pulmonary atresia, and TAPVR occur less often than they do in asplenia syndrome.
d. The ECG shows a superiorly oriented P axis (i.e., ectopic atrial rhythm), resulting from absence of the sinus node (Fig. 14-68).
e. Polysplenia syndrome occurs more often in females (70%).
Pathophysiology
Because PS or pulmonary atresia occurs less frequently, cyanosis is not intense, if it is present at all. Rather, CHF often develops because of increased PBF.
Clinical Manifestations
Physical Examination
1. Cyanosis is either absent or mild. Signs of CHF may develop during the neonatal period.
2. Heart murmur of VSD may be audible. A symmetrical liver is usually palpable.
Electrocardiography (see Fig. 14-68)
1. Ectopic atrial rhythm with a superiorly oriented P axis (−30 to −90 degrees) is seen in more than 70% of patients because there is no sinus node when two LA are present.
2. A “superior” QRS axis is present as a result of the presence of ECD.
3. RVH or LVH is common.
4. Complete heart block occurs in about 10% of patients.
Radiography
Mild to moderate cardiomegaly with increased pulmonary vascular markings; midline liver (see Fig. 4-8); and bilateral, hyparterial bronchi may be present.
Laboratory Studies
1. Some patients with splenic hypoplasia and hypofunction may have Howell-Jolly bodies but not in an excessive number.
2. The radioactive splenic scan may show multiple splenic tissues.
Echocardiography
Two-dimensional and Doppler echocardiographic studies reveal all or most of the cardiovascular malformations listed in Table 14-2 and help differentiate this syndrome from asplenia syndrome.
Other Imaging Modalities
Cardiac MRI or CT is often indicated because many patients with polysplenia syndromes have complex anomalies of pulmonary and systemic venous returns.
Natural History
1. The first-year mortality rate is 60% compared with greater than 95% in asplenia syndrome.
2. Most infants with severe cardiac malformations die within the first year without surgical palliation or repair.
3. The heart rate is lower than in normal children (because of the absence of sinus node). Excessive junctional bradycardia may develop, resulting in CHF.
Management
Medical
If present, CHF should be treated.
FIGURE 14-68 Tracing from a 1-week-old neonate with polysplenia syndrome. Both the P and the QRS axes are superiorly oriented (−45 and −150 degrees, respectively). The QRS voltages indicate right ventricular hypertrophy and possible additional left ventricular hypertrophy.
Surgical
1. PA banding should be performed if intractable CHF develops with large PBF.
2. Occasionally, pacemaker therapy is required for children with excessive junctional bradycardia and CHF.
3. Total correction of the defect is possible in some children. If total correction is not possible, at least a Fontan-type operation can be performed. The surgical mortality rate of the Fontan-type operation in this group of children is about 25%, which is lower than that for asplenia but higher than that for tricuspid atresia.
Postoperative Follow-up
Periodic follow-up is necessary because of continuing medical and surgical problems.
1. Although most patients are in NYHA class I or II (see Appendix A, Table A-3), persistent ascites or edema occurs frequently and requires medications such as digoxin, diuretics, and others for several years after the Fontan-type operation.
2. Cardiac arrhythmias, usually supraventricular, are present in 25% of patients. Some require antiarrhythmic medications.
Persistent Pulmonary Hypertension of the Newborn
Prevalence
Persistent pulmonary hypertension of the newborn (or persistence of the fetal circulation) occurs in approximately one in 1500 live births.
Pathology and Pathophysiology
1. This neonatal condition is characterized by persistence of pulmonary hypertension, which in turn causes a varying degree of cyanosis from a right-to-left shunt through the PDA or PFO. No other underlying CHD is present.
2. Various causes have been identified, but they can be divided into three groups by the anatomy of the pulmonary vascular bed:
a. Intense pulmonary vasoconstriction in the presence of a normally developed pulmonary vascular bed
b. Hypertrophy (of the medial layer) of the pulmonary arterioles
c. Developmentally abnormal pulmonary arterioles with decreased cross-sectional area of the pulmonary vascular bed (see Box 14-3 for further description)
BOX 14-3 Causes of Persistent Pulmonary Hypertension of the Newborn
Pulmonary vasoconstriction in the presence of a normally developed pulmonary vascular bed may be caused by or seen in:
Alveolar hypoxia (meconium aspiration syndrome, hyaline membrane disease, hypoventilation caused by CNS anomalies)
Birth asphyxia
LV dysfunction or circulatory shock
Infections (e.g., group B hemolytic streptococcal infection)
Hyperviscosity syndrome (polycythemia)
Hypoglycemia and hypocalcemia
Increased pulmonary vascular smooth muscle development (hypertrophy) may be caused by:
Chronic intrauterine asphyxia
Maternal use of prostaglandin synthesis inhibitors (aspirin, indomethacin) resulting in early ductal closure
Decreased cross-sectional area of pulmonary vascular bed may be seen in association with:
Congenital diaphragmatic hernia
Primary pulmonary hypoplasia
CNS, central nervous system; LV, left ventricular.
In general, pulmonary hypertension caused by the first group is relatively easy to reverse, and that caused by the second group is more difficult to reverse than that caused by the first group. Pulmonary hypertension caused by the third group is most difficult or impossible to reverse.
3. Varying degrees of myocardial dysfunction often occur in association with PPHN.
Clinical Manifestations
1. Symptoms begin 6 to 12 hours after birth, with cyanosis and respiratory difficulties (with retraction and grunting). The idiopathic form usually affects full-term or postterm neonates. The patient usually has a history of meconium staining or birth asphyxia. A history of maternal ingestion of nonsteroidal antiinflammatory drugs (in the third trimester) may be elicited.
2. A prominent RV impulse and a single and loud S2 are usually found. Occasional gallop rhythm (from myocardial dysfunction) and a soft regurgitant systolic murmur of TR may be audible. Severe cases of myocardial dysfunction may manifest with systemic hypotension.
3. Arterial desaturation is found in blood samples obtained from an umbilical artery catheter. Arterial Po2, may be lower in the descending aorta (the umbilical artery line) than in the preductal arteries (the right radial, brachial, or temporal artery) by 5 to 10 mm Hg because of a right-to-left ductal shunt. In severe cases, differential cyanosis may appear (with a pink upper body and a cyanotic lower body). If there is a prominent right-to-left intracardiac shunt, usually through the PFO, the preductal and postductal arteries may not show a Po2 difference.
4. The ECG usually is normal for age, but occasional RVH is present. T-wave abnormalities suggestive of myocardial dysfunction may be seen.
5. Chest radiography reveals a varying degree of cardiomegaly. The lung fields may be free of abnormal findings or may show hyperinflation or atelectasis. The pulmonary vascular markings may appear normal, increased, or decreased.
6. Echocardiographic and Doppler studies are indicated to rule out CHDs and to identify patients with myocardial dysfunction. Patients with PPHN have no evidence of cyanotic or acyanotic CHDs. The only structural abnormality is the presence of a large PDA with a right-to-left or bidirectional shunt. The RV is enlarged with a flattened interventricular septum. There is evidence of increased RA pressures (with the atrial septum bulging toward the left) with or without an ASD or PFO. The LV dimension may be increased, and its systolic function (fractional shortening or ejection fraction) may be decreased.
7. Cardiac catheterization usually is not indicated. If the diagnosis is unclear or the patient does not respond to therapy, cardiac catheterization and pulmonary arteriography rarely are considered.
Management
The goals of therapy are to (1) lower the PVR and PA (PA) pressure through the administration of oxygen, the induction of respiratory alkalosis, and the use of pulmonary vasodilators; (2) correct myocardial dysfunction; and (3) stabilize the patient and treat associated conditions. Detailed description of management for each goal is beyond the scope of this book; only principles of management will be presented.
1. General supportive therapy includes monitoring oxygen saturation; detecting and treating hypoglycemia, hypocalcemia, hypomagnesemia, and polycythemia; and maintaining body temperature between 98° and 99°F (36.6° and 37.2°C).
2. To increase arterial Po2 levels, 100% oxygen is administered, initially without intubation. If this is not successful, intubation plus continuous positive airway pressure at 2 to 10 cm of water may be effective.
3. If the previous measures are not successful, mechanical ventilation with 100% oxygen is used to produce respiratory alkalosis. Ventilator settings are initially set to achieve Po2 of 50 to 70 mm Hg and PCO2 of 50 to 55 mm Hg. The patient usually is paralyzed with pancuronium (Pavulon) at 0.1 mg/kg IV. However, use of paralytic agents is controversial because it may promote atelectasis of dependent lung regions with resulting ventilation–perfusion mismatch.
4. Maintaining a normal or alkaline pH level can also be achieved with the use of sodium bicarbonate or tromethamine (THAM) infusion may promote pulmonary vasodilatation and improve oxygenation.
5. Tolazoline (Priscoline), a nonselective α-adrenergic antagonist, is sometimes used. Tolazoline, being a nonselective vasodilator, also lowers SVR, resulting in systemic hypotension. Other side effects of tolazoline include increased gastric secretion, gastrointestinal bleeding, decreased platelet counts, and decreased urine output. Cimetidine (a histamine H2 receptor antagonist) is not recommended because it may block the action of histamine, which is a known pulmonary vasodilator.
6. For myocardial dysfunction, dopamine is used with tolazoline to improve cardiac output. Correction of acidosis, hypocalcemia, and hypoglycemia helps improve myocardial function. Diuretics may be included in the regimen. For chronic myocardial dysfunction, digoxin may be added at a later stage.
7. A high-frequency oscillatory ventilator is effective in patients with severe PPHN. Through the use of this device; about 40% of patients who would be candidates for extracorporeal membrane oxygenation (ECMO) can avoid this procedure.
8. Inhalation nitric oxide (iNO) is a potent and selective pulmonary vasodilator. The usual starting dose is 20 ppm. Prolonged low-dose NO therapy has caused sustained improvement in oxygenation without systemic hypotension. Most newborn infants require iNO for fewer than 5 days. The use of iNO in PPHN has decreased the need for ECMO by approximately 40%. When administered by inhalation, NO diffuses to vascular smooth muscle, stimulating the production of cyclic guanosine monophosphate and causing vasodilatation.
9. ECMO has been shown to be effective in the management of selected patients with severe PPHN. However, this treatment may require ligation of a carotid artery and the jugular vein, and cerebrovascular accidents have been reported.
Prognosis
1. Prognosis generally is good for neonates with mild PPHN who respond quickly to therapy. Most of these neonates recover without permanent lung damage or neurologic impairment.
2. For those requiring a maximal ventilator setting for a prolonged time, the chance of survival is smaller, and many survivors develop bronchopulmonary dysplasia and other complications.
3. Patients with developmental decreases in cross-sectional areas of the pulmonary vascular bed usually do not respond to therapy, and their prognosis is poor.
4. Neurodevelopmental abnormalities may manifest. Patients have a high incidence of hearing loss (≤50%). Abnormal electroencephalogram findings (≤80%) and cerebral infarction (45%) have been reported.
∗ This occurs in all types of cyanotic CHDs.