Prevalence
Cardiac tumors in the pediatric age group are extremely rare. A primary cardiac tumor was diagnosed in 0.001% to 0.003% of admissions at large children’s referral centers. The male-to-female distribution is equal.
Pathology
Types and Frequency of Tumors
Table 22-1 shows the relative incidence of cardiac tumors in infants and children (Becker, 2000). Becker’s data include 55 cases from Armed Forces Institute of Pathology, Washington, DC, series 3f, and 21 cases from the Cardiovascular Pathology Registry in the Academic Medical Center, Amsterdam, Netherlands. Data in Table 22-1 show the following.
1. A large portion of primary heart tumors in the pediatric age group presents at less than 1 year of age.
2. The most common cardiac tumor in the pediatric age group is rhabdomyoma. In infants younger than 1 year old, more than 50% of tumors are rhabdomyomas followed by fibromas (25%). In children 1 to 16 years of age, nearly 40% of benign tumors are fibromas and myxomas (see Table 22-1). Rhabdomyomas accounted for only 8% of benign tumor in this age group.
3. More than 90% of primary tumors are benign in infants. Although primary malignant tumors are extremely rare in infants (≈5%), approximately 40% of primary tumors were malignant in children older than 1 year of age. Malignant tumors reported in children include rhabdomyosarcoma, leiomyosarcoma, angiosarcoma, fibrosarcoma, and many others.
Recently, 120 operated cases of cardiac tumors in infants and children were reported by Bielefeld et al (2012). Although the data are not presented according to two age groups, younger than 12 months and older than 12 months, a similar trend exists with earlier reports. Rhabdomyomas were the most frequent, representing 35% of pediatric cardiac tumors (mean age, 7 months). Myxomas were the second most frequent (23%) with a mean age of 9 years. Fibromas represented 20% of the cases with a mean age of 3.25 years. These three tumor types accounted for three fourths of all surgically treated pediatric cardiac tumors.
Pathology of Individual Cardiac Tumor
Common pediatric cardiac tumors are briefly summarized in this chapter.
Rhabdomyoma
1. Rhabdomyomas are by far the most frequent tumors in the pediatric age group, accounting for about half the cases of cardiac tumors.
2. They usually are multiple, ranging in size from several millimeters to several centimeters. The most common location is in the ventricles, either in the ventricular septum or free wall, but they may rarely appear in the atrium.
TABLE 22-1
RELATIVE INCIDENCE OF CARDIAC TUMORS IN INFANTS AND CHILDREN∗
∗ Rearranged data from Becker AE. Primary heart tumors in the pediatric age group: a review of salient pathologic features relevant fro clinicians. Pediatr Cardiol 21:317-323, 2000.
3. More than half the children with multiple rhabdomyomas have tuberous sclerosis (e.g., with adenoma of the sebaceous glands, mental retardation, seizures).
4. Tumors regress in size or number or both in most patients younger than 4 years of age (but less so in older patients) (Nir et al, 1995). Spontaneous complete regression may occur.
5. The tumors may produce symptoms of obstruction to blood flow, arrhythmias (usually ventricular tachycardia, occasionally supraventricular tachycardia), or sudden death.
6. Cardiac rhabdomyomas are associated with a higher incidence of Wolff-Parkinson-White (WPW) preexcitation and may increase the risk for arrhythmias.
Fibroma
1. Fibroma is the second most common tumor type encountered in infants and small children.
2. Cardiac fibromas usually occur as a single solid tumor, most commonly in the ventricular septum, although they may also occur in the wall of any cardiac chamber. The size of the tumor varies from several millimeters to centimeters. Occasionally, the tumor calcifies.
3. The tumor may obstruct blood flow and disturb atrioventricular (AV) or ventricular conduction.
4. In some cases, the tumor can be removed completely, but in others, the tumor intermingles with myocardial tissue so that complete resection is not possible. The tumors probably represent hamartomatous lesions that may eventually regress. This has led to a tendency for a less aggressive surgical resection to reduce potential risks for complications.
Myxoma
1. Myxomas are the most common type of cardiac tumors in adults, accounting for about 30% of all primary cardiac tumors, but they are very rare in infants and children.
2. The majority of myxomas arise in the left atrium, 25% arise in the right atrium, and very few arise in the ventricles.
3. Myxomas can produce hemodynamic disturbances, commonly interfering with mitral valve function or producing thromboembolic phenomena in the systemic circulation. With right atrial myxoma, similar effects on the tricuspid valve and thromboembolic phenomena in the pulmonary circulation may be found. Rarely, patients may have symptoms while sitting and standing, but their symptoms improve when they lie down because of the intermittent protrusion of the tumor through the mitral valve.
4. Surgical removal usually is successful.
Teratoma
1. Teratomas contain elements from all three germ layers.
2. Most of the tumors are intrapericardial and are attached to the root of the aorta and pulmonary trunk, but the heart wall can be involved, and occasionally they may present as an intracardiac mass.
3. Surgical excision is usually possible.
Cardiac Angioma
1. This is a relatively rare tumor in infants and children.
2. They show preference for the epicardium, in which they may produce hemopericardium. Intramyocardial location may cause myocardial dysfunction, AV block, or both.
3. They do not grow rapidly, and spontaneous involution has been documented.
Clinical Manifestations
1. Cardiac tumors usually are found on routine echocardiographic studies when the diagnosis is not suspected, especially in small infants.
2. Syncope or chest pain may be a presenting complaint in older children. Sudden unexpected death may be the first manifestation. Rarely, symptoms vary with posture in cases of pedunculated tumors (e.g., myxoma).
3. Clinical manifestations of cardiac tumors often are nonspecific and vary primarily with the location and the size of the tumor.
a. Tumors near cardiac valves may produce heart murmurs of stenosis or regurgitation of valves. So-called tumor plop may occur with a pedunculated and sessile tumor, such as a left atrial myxoma.
b. Tumors involving the conduction tissue may manifest with arrhythmias or conduction disturbances (such as seen with fibromas).
c. Intracavitary tumors may produce inflow or outflow obstruction (such as seen with rhabdomyoma), with clinical findings similar to those of mitral or semilunar valve stenosis.
d. Involvement of the myocardium (mural tumors) may result in heart failure or cardiac arrhythmias.
e. Pericardial tumors, which may signal malignancy, can produce pericardial effusion and cardiac tamponade or features simulating infective pericarditis.
3. Fragmentation of intracavitary tumors may lead to embolism of the pulmonary or systemic circulations (as seen with myxoma).
4. Occasionally, for unknown reasons, fever and general malaise may manifest, especially with myxomas.
5. The ECG may show nonspecific ST-T changes, an infarct-like pattern, low-voltage QRS complexes, or WPW preexcitation. Various arrhythmias and conduction disturbances have been reported.
6. Chest radiographs occasionally may reveal altered contour of the heart with or without changes in pulmonary vascular markings.
Diagnostic Procedures
1. Two-dimensional Doppler echocardiography is the primary tool for the evaluation of cardiac tumors in pediatric patients. Echocardiography and Doppler studies allow accurate determination of the extent and location of the tumor as well as the hemodynamic significance of the lesion.
a. Multiple intraventricular tumors in infants and children most likely are rhabdomyomas (Fig. 22-1).
b. A solitary tumor of varying size, arising from the ventricular septum or the ventricular wall, is likely to be a fibroma (Fig. 22-2).
c. Left atrial tumors, especially when pedunculated, usually are myxomas (Fig. 22-3).
d. An intrapericardial tumor arising near the great arteries most likely is a teratoma.
e. Pericardial effusion suggests a secondary malignant tumor.
FIGURE 22-1 Parasternal long-axis view (A) and diagram (B) of multiple rhabdomyomas (T) in a newborn. There is a round, mobile mass in the left ventricular outflow tract, with resulting obstruction. One large and at least two other smaller tumor masses are imaged in the right ventricle (RV). The tumor in the left ventricular outflow tract was surgically removed because of the obstructive nature of the mass. AO, aorta; IVS, interventricular septum; LA, left atrium.
FIGURE 22-2 Apical four-chamber view (apex up) (A) and diagram (B) of a large solitary tumor in the left ventricular (LV) cavity in a newborn. The mass is attached to the LV free wall. Because of symptoms, a surgical attempt was made to remove the mass, but the infant died. Pathologic examination revealed the mass to be fibroma. AO, aorta; LA, left atrium; RA, right atrium; RV, right ventricle.
FIGURE 22-3 Four-chamber view of the transverse plane of a transesophageal echo from a 54-year-old man with left atrial myxoma (T). A, A systolic freeze frame showing a large oval mass in the left atrium (LA). This mass is attached to the atrial septum. The primum atrial septum is also thickened. B, During diastole, the myxoma protrudes through the mitral valve. LV, left ventricle; RA, right atrium; RV, right ventricle.
2. Transesophageal echocardiography can provide more precise delineation of the tumor before and during surgery.
3. Magnetic resonance imaging (MRI) also provides the same information as the two-dimensional echo study does. MRI techniques have certain advantages over echocardiographic study.
a. MRI provides high-resolution images of cardiac cavitary, valvular, myocardial, pericardial, and extracardiac masses in addition to its relationship with mediastinal and other intrathoracic structures.
b. MRI can provide spatial relationship of the tumor mass to the coronary arteries, which may help guide surgical management.
c. MRI allows differentiation of tumors from myocardium and differentiation of the type of tumor, such as cardiac hemangiomas from rhabdomyomas and fibromas.
d. MRI is better than echocardiography in detecting apical tumors.
4. Cardiac catheterization and angiography are usually not necessary. Attempts at tissue diagnosis can be risky because of possible embolization of tumor fragment.
Management
Surgery is the only treatment for cardiac tumors that require intervention. Surgery is indicated in patients with inlet or outlet obstruction and in patients with symptoms of cardiac failure or ventricular arrhythmias refractory to medical treatment.
1. Rhabdomyomas: Spontaneous regression of these tumors has been well established so that surgical intervention is no longer indicated unless the tumors produce obstruction or arrhythmias refractory to medical treatment.
2. Fibromas: A successful complete resection of a fibroma is possible. In some cases, the tumor intermingles with myocardial tissue so that complete resection is not possible without causing damage to the myocardium or conduction tissues. Fibromas accounted for the highest surgical mortality rate (33%). Currently, there is a tendency for less than radical surgical resection because cardiac fibromas probably represent hamartomatous lesions that may regress spontaneously.
3. Surgical removal is a standard procedure for myxomas and has a favorable outcome. The stalk of the tumor should be removed completely to prevent recurrence.
4. If myocardial involvement is extensive, surgical treatment is not possible. Cardiac transplantation may be an option in such cases.