IMAGING OF THE HEART AND GREAT VESSELS: INTRODUCTION

The heart and great vessels are complex structures that are critically important to human function. They serve as the "pump" and major proximal "pipes" distributing blood and nutrients to the body. This chapter describes the normal radiographic appearance of the heart, pericardium, and great vessels (aorta and pulmonary vessels) and briefly outlines some of the more common pathologic entities in this organ system. Critical evaluation of the findings on the imaging examinations of this region is not possible without paying attention to the lungs, because these two organ systems mirror changes in each other. The most common abnormalities encountered in the cardiovascular system are hypertension, pulmonary arterial hypertension (usually secondary to chronic pulmonary disease), congestive heart failure, atherosclerotic disease, and valvular disease. Less common cardiac and great vessel diseases such as congenital heart disease, neoplasms, and diseases of the pericardium are described in less detail. The last topic of monitoring devices and postoperative changes is one with which students should be familiar.

We are assuming that the student understands the basic normal anatomy of the cardiovascular system from the basic science and clinical years. At the completion of this chapter the student should have an understanding of the wide range of imaging modalities used, an appreciation for the potential yield from these examinations, a basic knowledge of the normal imaging anatomy on the conventional radiograph, and a familiarity with more common postoperative alterations and the various monitoring devices that may be present in the intensive care unit.

TECHNIQUES AND NORMAL ANATOMY

A variety of techniques have been developed to evaluate the heart and great vessels (Table 3–1). In this section, we briefly describe the major tests used in imaging this system.

Conventional Radiographs

The most common imaging test for evaluating the heart and great vessels is the chest radiograph, which consists of an upright posterior-to-anterior (PA) and left lateral (LAT) projections. The terms PA and left lateral refer to the direction the x-ray beam takes through the body before it reaches the radiographic cassette. Chest radio-graphs are usually obtained with high kilovoltage and milliamperage to minimize exposure time and cardiac motion. When possible, the distance between the x-ray tube source and the film is at least 6 feet to minimize magnification and distortion.

The examination is ideally performed with the patient at maximal inspiration. A good rule of thumb for estimating adequate inspiration is to be able to count 9 to 10 posterior ribs or 5 to 6 anterior ribs from the lung apices to the hemidiaphragms through the aerated lungs (Fig. 3–1). When a chest radiograph is taken in the expiratory phase of respiration, the patient may appear to have cardiomegaly, vascular congestion, and even pulmonary edema. This appearance, however, is merely artifactual and caused by poor inspiration (Fig. 3–2).

Severely ill, debilitated patients or patients who cannot be transported to the radiology department can have their chest radiographs obtained with a portable x-ray machine. Patients in the intensive care unit (ICU) who have intravascular catheters or who are undergoing mechanical ventilation frequently have chest radiographs performed as a survey for complications that may not be revealed by physical examination or laboratory data. These examinations are done with the cassette placed behind the patient in bed and are therefore anterior-to-posterior (AP) projections. The technical factors, which are controlled by the technologist at the time of the examination, vary with the size of the patient and the distance of the radiographic plate from the x-ray source (or machine). An attempt is still made to obtain the examination during maximum inspiration but this objective may be difficult to achieve in some patients, especially those who have dyspnea.

With the patient in the supine position, there is normally a redistribution of blood flow to the upper lobe pulmonary veins (cephalization), and the heart may appear enlarged relative to its appearance on the upright PA radiograph, because of magnification (Fig. 3–3). Some patients are able to sit for their examinations, while others are radiographed in a semi-upright position. Ideally, the technologist should mark the exact position of the patient when the radiograph is obtained, and the date and time of the examination should be recorded in all cases. Changes in patient positioning and ventilator settings can have substantial effects on the radiographic appearance and must be taken into account when evaluating any change in the radiograph from a previous study.

The chest radiograph, whether it is obtained in the upright, semi-upright, sitting, or supine position, should always be the initial screening examination in the evaluation of the cardiovascular system. Because it is essentially a screening study, the chest x-ray must be correlated with the clinical symptoms and physical examination to determine the overall significance of the radiographic findings. This information is also used to decide if other imaging tests are appropriate and which ones will potentially result in the highest diagnostic yield. Decisions regarding further imaging also depend on the impact on the clinical management of the patient, the potential for treatment of any abnormality that may be discovered, the cost and availability of the technique, and the expertise of the interpreting radiologist.

The conventional radiograph is an excellent screening test for the patient suspected of having disease involving the heart and great vessels because the overall anatomy of these areas is demonstrated well. Whenever possible, all radiographs should be reviewed with all prior relevant imaging studies. Even when a prior chest radiograph is not available, additional information may be ascertained by reviewing other prior images such as thoracic spine or rib-detail image when available. Advanced imaging studies such as computed tomography (CT) and magnetic resonance (MR) imaging can also be used to help clarify complex findings on chest radiographs.

The normal cardiac silhouette size may be determined by the cardiothoracic ratio (CT ratio), a measurement obtained from the PA view. This ratio is calculated by dividing the transverse cardiac diameter (measured from each side) by the widest diameter of the chest (measured from the inner aspect of the right and left lung fields near the hemidiaphragms). The average normal value for this ratio in adults is 0.50, although up to 60% may be normal (Fig. 3–4). Any measurement greater than 50% is usually considered abnormal in an upright inspiratory-phase PA film. This CT ratio cannot be reliably used for the AP projection of the chest since the heart is magnified (Fig. 3–3). The size of the patient and the degree of lung expansion also should be considered. For instance, in a small person with a petite frame and a small thoracic cage, the heart size may be normal, but the cardiothoracic ratio may measure more than 50%. Similarly, if the patient has pulmonary disease such as emphysema, the heart may be enlarged, but because of the overinflation of the lungs, the cardiothoracic ratio may still be normal. In practice, most radiologists do not perform this measurement and instead rely on experience and "gestalt" to evaluate heart size.

The contours of the heart, mediastinum, and great vessels on the PA view should be evaluated on each chest film (Fig. 3–1A ). A reasonable approach is to begin in the upper right side of the mediastinum just lateral to the spine and below the right clavicle. The curved soft-tissue shadow represents the right border of the superior vena cava (SVC). Below the SVC is the right cardiac border formed by the right atrium. The inferior heart border, or base of the heart, is the area just above the diaphragm and is comprised primarily of the right ventricle, although there is some contribution from the left ventricular shadow. The left ventricle makes up the majority of the apex of the heart, which points to the left of the spine. The origins of the right and left pulmonary arteries are generally well demarcated on the normal PA film as they emerge from the mediastinum. The most prominent and recognizable component of the right pulmonary artery, the right descending pulmonary artery (RDPA) is seen just to the right of the superior cardiac border and descends inferiorly. It can usually be easily followed until it branches. The left main pulmonary artery is less well defined, but its origin can usually be seen above and lateral to the left atrial appendage just before it branches. The aorta originates posterior and to the right of the main pulmonary artery and the border of the ascending portion of the aorta can usually be seen superimposed on the inferior portion of the SVC. The transverse arch is not outlined by air and therefore cannot be seen as it crosses the mediastinum. However, the descending aorta can be seen to the left of the mediastinum as it turns inferiorly. The left border of the descending thoracic aorta should be followed down to the aortic hiatus. Any loss of this contour or any contour abnormality may indicate pathology and should be investigated. Dilation or ectasia, localized bulges, and calcification may occur within the aorta as a normal part of the aging process, but should be viewed as abnormal in younger individuals. Of course, the spine, ribs, adjacent soft tissues, and upper abdominal contents should all be scrutinized. The left atrium lies just inferior to the tracheal carina, but it is usually not visualized as a discrete structure on the normal PA view. Signs of left atrial enlargement, which can be seen on the PA examination, are discussed later.

The lateral view of the chest also reveals important information regarding the cardiac contour (Fig. 3–1B ). Just behind the sternum there is normally a radiolucent area called the retrosternal clear space (RSS). This region represents lung interposed between the chest wall and the anterior margin of the ascending aorta. Any density present within the RSS may be due to anterior mediastinal mass or postsurgical changes. The anterior border of the cardiac shadow is composed primarily of the anterior wall of the right ventricle. Right ventricular enlargement may also encroach into the RSS. The posterior margin of the cardiac silhouette is formed by the left atrium and left ventricle. Just posterior and inferior to the left ventricle is a linear soft-tissue shadow leading into the heart formed by the inferior vena cava (IVC). The left ventricular shadow should not project more than 2 cm posterior to the posterior border of the IVC. The transverse aortic arch can usually be discerned on the normal lateral chest film as a smooth curving shadow originating anteriorly, crossing the mediastinum in a semilunar fashion, and then descending posteriorly as a linear shadow superimposed over the vertebral bodies. The left pulmonary artery (LPA) produces a similar curvilinear shadow just below the aortic arch before it branches. Just below the LPA, the left main/left upper lobe bronchus can be seen (projected end-on) as a round lucency. The right pulmonary artery (RPA) is seen en face down its lumen as an oval soft-tissue structure anterior to the bronchus intermedius and below and anterior to the left pulmonary artery.

Echocardiography

Echocardiography uses high-frequency ultrasound to evaluate the heart and great vessels. The major indications for the technique are listed in Table 3–2. The examination provides a dynamic rendition of cardiac great vessel anatomy and, when combined with the Doppler technique, yields information regarding cardiac and great vessel blood flow (hemodynamics) as well. Because of the high frame rates inherent in ultrasonography, echocardiography can image the heart in a dynamic real-time fashion, so that the motion of cardiac structures can be reliably evaluated. Echocardiography is useful in assessing ventricular function, valvular heart disease, myocardial disease, pericardial disease, intracardiac masses, and aortic abnormalities (Figs. 3–5 and 3–6). With Doppler technology the cardiac chamber function, valvular function, and intracardiac shunts frequently seen in congenital heart disease can be assessed. Combined Doppler echocardiography is a commonly performed procedure because it is relatively inexpensive and widely available, provides a wealth of information, is noninvasive, has no risk of ionizing radiation, and can also be performed at the bedside of critically ill patients. Furthermore, the results are immediately available because no special postexamination image processing is required. However, this technique is technically challenging and requires a great deal of operator expertise. Also, a small percentage of patients have poor acoustic windows that can severely degrade image quality. This disadvantage can be obviated by placing the sonographic probe in the esophagus, a procedure called transesophageal echocardiography (TEE). TEE yields consistently excellent images of the heart and great vessels, but involves a small amount of discomfort and risk to the patient. More recently, echocardiography has been combined with stress-testing modalities to assess inducible myocardial ischemia using wall motion analysis of left ventricular function.

Radionuclide Imaging (Nuclear Medicine)

Cardiac radionuclide imaging, primarily used for the patient with suspected myocardial ischemia or infarction, requires an intravenous injection of radioactively labeled compounds that have an affinity for the myocardium. These compounds localize within the myocardium in diseased or damaged areas, and a radioactivity detector such as a gamma camera can image their distribution. These tests are most commonly used in the evaluation of patients with angina and atypical chest pain (Fig. 3–7). Positron emission tomography (PET) is an investigational tool that has shown promise in assessing myocardial viability in patients with known coronary artery disease who represent a therapeutic dilemma after they are evaluated with other imaging modalities (Fig. 3–8). This technique, however, has tremendous clinical potential and will likely become a valuable technique in the future.

Computed Tomography

Current helical and multislice CT scanners provide static axial images of the heart and great vessels (Fig. 3–9) and can be reformatted into coronal, sagittal, and oblique views. Coupled with ECG gating, motion of the heart can be greatly diminished. The major indications for CT are to characterize or confirm a suspected mediastinal or pulmonary mass seen on PA and lateral chest radiographs, to evaluate patients suspected of having an aortic abnormality, or to assess for pulmonary embolism. It is hoped that as it becomes feasible to rotate the CT gantry faster, noninvasive imaging of the coronary arteries will become a reality. At the present time, some physicians use the measurement of calcium in the coronary arteries detected at CT to stratify the risk of future cardiovascular events (Fig. 3–10). Contrast administration is mandatory when questions arise that are related to intrinsic cardiac anatomy or abnormalities of the thoracic aorta such as dissection or for evaluation of the pulmonary arteries for pulmonary embolism. For many of these applications rapid administration of contrast is necessary (up to 4–5 cc/sec) and a well-functioning large-bore (at least 18- to 20-gauge) IV catheter must be present to ensure a high-quality study.

Magnetic Resonance Imaging

MR imaging has also gained rapid acceptance for cardiac evaluation because it does not use ionizing radiation, can provide morphologic and physiologic data, and can be performed to give cine-loop images. Using high-field-strength magnets to generate images by radio-frequency pulse manipulation of hydrogen atoms, MR imaging offers superb soft-tissue differentiation, is noninvasive, and usually requires no contrast material administration (Fig. 3–11). Unfortunately, the time and effort needed to perform this examination makes MR imaging largely a problem-solving tool, rather than a screening study. The major indications for MR imaging are congenital heart disease and suspected intracardiac masses, valvular dysfunction, and aortic abnormality (in particular, aortic dissection). MR imaging has also shown some promise in diagnosing pulmonary embolism, measuring the degree of damage from coronary artery atherosclerosis, and evaluating the composition of atherosclerotic plaque.

Angiography

Coronary angiography is one of the most commonly performed imaging tests for evaluating the heart and great vessels. After the introduction of a catheter into a peripheral vessel (usually the femoral or axillary vein or artery), the angiographer, under fluoroscopic visualization, positions the catheter in the region of interest, injects contrast material to confirm the location of the catheter, and then injects larger amounts of contrast material for diagnostic purposes. This injection of contrast material can be videotaped, recorded as standard or digital radiographs, or digitally stored for later review. The four major types of angiography are angiocardiography (heart), coronary arteriography (coronary arteries), aortography (aorta), and pulmonary angiography (pulmonary arteries and lungs). Developed by radiologists, angiocardiography and coronary arteriography are now almost exclusively performed by cardiologists.

Angiocardiography is used primarily to evaluate ventricular contractility and wall motion and cardiac output in patients with suspected myocardial dysfunction. It is also used to evaluate cardiac valvular function in patients who have murmurs detected at physical examination. The purpose of coronary arteriography is to define the degree of coronary artery obstruction, usually caused by atherosclerosis. In this procedure a catheter is generally placed into the origin of each coronary artery orifice and contrast material is injected into the arteries and videotaped or filmed, as described earlier (Fig. 3–12). Coronary angiography can also be performed in the acute setting of suspected coronary occlusion, and a balloon catheter or thrombolytic agent can be placed through the catheter in an attempt to relieve the coronary artery obstruction.

Aortography is used primarily to evaluate suspected aortic disease (Fig. 3–13A ). Although aortography remains the standard for traumatic injury (Fig. 3–13B ), CT has largely replaced aortography. Pulmonary angiography is also declining in interest and use due to improvements in helical CT. Today one of the more common uses of pulmonary angiography is to treat massive pulmonary embolism with thrombolytic therapy or treat arteriovenous malformations. Pulmonary artery catheterization is also used to measure the pulmonary artery pressures in patients suspected of having pulmonary arterial hypertension.

TECHNIQUE SELECTION

A wide array of imaging tests can be used to evaluate the cardiovascular system (Table 3–1). After a thorough history and physical examination, the initial screening study should always be a chest radiograph. Ideally the PA and lateral views should be obtained with maximum inspiration. This study gives important information about the cardiac contour and the status of the lungs and is a good examination for excluding disorders that would require immediate treatment, such as pneumothorax. Furthermore, evaluation of the chest radiograph can often lead to a specific diagnosis and treatment or can help determine the need for another imaging study.

Depending on the history and physical examination findings, echocardiography and cardiac angiography are probably the most commonly performed secondary imaging examinations. Echocardiography is a good screening test to assess cardiac and great vessel valvular motion and structural abnormalities, cardiac chamber morphology, and flow. Angiography delineates the structural status of the coronary arteries and can give information on blood flow through the cardiac chambers, valves, and proximal great vessels, mainly in patients with suspected atherosclerosis. It is also used to guide interventions such as stent placement in the coronary arteries. Because of its inherent risks, coronary arterio-graphy is usually reserved for patients with signs and symptoms of myocardial ischemia or infarction either on the basis of history or results of electrocardiography, echocardiography, or radionuclide myocardial imaging.

In patients with suspected pulmonary emboli, helical CT is the most appropriate test in the setting of an abnormal chest x-ray (Fig. 3–14). The ventilation-perfusion (V/Q) scan can be performed if the chest radio-graph is normal. It is also the preferred examination in young females due to the radiation dose to the breast by CT. Both of these tests can confirm the clinically suspected diagnosis of pulmonary embolic disease and often provides a useful "map" of the most suspicious regions of the lung for the angiographer if an angiogram is required for the definitive diagnosis of pulmonary embolism. CT can also detect alternative important diagnoses not detected by either V/Q scan or pulmonary angiography.

Echocardiography, MR imaging, or cardiac angiography may be selected for patients with suspected congenital heart disease. The advantages of MR imaging in this setting is that it is noninvasive, generally needs no contrast material administration, and uses no ionizing radiation, an important consideration in the pediatric patient. For these reasons, MR imaging has become the preferred imaging test in the pediatric population.

Suspected aortic dissection (either atherosclerotic or traumatic in origin) can be evaluated by helical CT, TEE, aortography, or MR imaging. Helical CT is the imaging modality of choice for acute dissection due to its accuracy and availability (Fig. 3–15). With multislice technology, CT angiography can provide images in multiple planes to show the relation of the dissection to key branch vessels. TEE has the advantages of being quick and noninvasive, and the examination can be performed expediently at the bedside. MR imaging is noninvasive, uses no ionizing radiation, is less operator dependent, and can be performed in multiple planes. It is limited by availability, imaging time, and because it cannot be used in patients with certain implanted devices, particularly pacemakers. Angiography has mostly been relegated to minimally invasive treatments such as stent-graft placement. Because survival rates often depend on early surgical intervention, the availability and timeliness of the examinations are important.

In patients whose chest radiographs suggest intrinsic pulmonary or mediastinal processes, chest CT is currently the preferred modality. The use of contrast depends on the indication, preference of the radiologist, and any possible contraindications to administration of intravenous contrast for individual patients. MR imaging may become more important in this situation if it becomes less costly and, at the present time, PET plays a critical role in the staging of patients with lung cancer and lymphoma.

Finally, regardless of the situation, it is reasonable for the clinician and radiologist to decide together which imaging tests are most appropriate. In many instances the next most efficacious and least costly imaging examination is not always clear-cut. In fact, in some circumstances, it is not necessary to perform another test because of the limited potential yield from the examination or because there is no adequate therapy for the suspected abnormality. It is hoped that future recommendations for test selection will be determined by well-designed prospective unbiased outcome studies comparing all of these modalities in various clinical scenarios. In the meantime, a commonsense approach, taking into consideration the history and physical examination findings, the information gleaned from the conventional radiograph, and the potential yield from the array of other available imaging tests, is the most appropriate tact. In all instances, communication between the clinician and radiologist is critical for the best patient care.

Monitoring Devices

In clinical hospital practice, particularly in the ICU setting, a variety of catheters and tubes are used to monitor various parameters in patients (Fig. 3–16). The student should be familiar with the normal routes and positions of these devices, as well as inappropriate positions and complications. Table 3–3 lists the most common monitoring devices.

The basic venous anatomy of the upper mediastinum should be reviewed and kept in mind when evaluating catheter placement. The most common routes of catheter insertion in the chest include the internal jugular and subclavian veins. Radiographs obtained after insertion show the catheter following either the course of the internal jugular or subclavian vein and passing through the brachiocephalic vein. It then curves gently downward to terminate in the superior vena cava proximal to the right atrium (Fig. 3–17). One normal variation of venous anatomy is the persistent left superior vena cava. In this situation the catheter descends down the left mediastinum terminating in the left SVC (Fig. 3–18). The left SVC ultimately drains into the coronary sinus, which then enters the right atrium.

Intrathoracic central venous catheters are used mainly for monitoring central venous pressure (CVP), maintaining proper nutrition, delivering medication, and conducting hemodialysis. It is standard practice to request a chest radiograph after catheter placement to verify its location and to check for potential complications, such as pneumothorax (Fig. 3–19) or hemothorax. Measurement of CVP is optimally obtained when the tip of the catheter is proximal to the right atrium and distal to the most proximal valves of the large veins. A catheter tip proximal to the veins gives an inaccurate reading of CVP, and a tip too close to the right atrium may cause arrhythmias from irritation of the right atrial myocardium. Knowing why a catheter has been inserted is of critical importance to the radiologist in determining if the catheter has been appropriately positioned. For instance, if it has been placed just for fluids and/or medications, a termination in the brachiocephalic vein is satisfactory. Conversely, a plasmapheresis catheter should never be located in the right atrium due to the risk of complications. More frequently, central venous catheters are being placed centrally via a peripheral vein. These catheters have minimal risk, can remain in place for longer periods of time without being exchanged, and are primarily used for the delivery of fluids and long-term antibiotics.

The major potential complications from catheter placement are outlined in Table 3–4. A malpositioned central venous catheter may result in inaccurate CVP measurement, thrombosis, catheter knotting, and infusion of substances into the mediastinum or pleura. Catheter tips against the wall of the SVC may erode into the mediastinum or may extend retrograde into tributary veins, particularly the azygous vein (Fig. 3–20).

Flow-directed arterial catheters are also regularly used in cardiac and ICU patients to monitor cardiac output. The most common flow-directed catheter is the Swan-Ganz (SG) catheter (Fig. 3–16). It is usually inserted percutaneously into the left or right subclavian vein and threaded through the brachiocephalic vein, superior vena cava, right atrium, tricuspid valve, right ventricle, and pulmonic valve, and then directed out into the main pulmonary artery. Usually terminating in the right or left pulmonary arteries, the SG tip should be distal to the pulmonary valve and proximal to the smaller pulmonary arterial vessels so it will not cause occlusion and, potentially, thrombosis. A simple rule of thumb is that the catheter should not extend past the mediastinal borders. It may then be intermittently "wedged" into a distal pulmonary artery branch to obtain a pulmonary capillary wedge pressure.

Complications of SG catheter placement are similar to other central venous catheters. The tip may be positioned in a number of inappropriate vessels or locations, and a chest radiograph should be obtained after catheter insertion to confirm its position (Fig. 3–21). Introduction of any catheter into the subclavian vein, because of its proximity to the lung apex, can cause pneumothorax (Fig. 3–19). A catheter tip positioned in the right ventricle can lead to ventricular arrhythmias, and leaving the catheter tip too distal may result in a pulmonary artery pseudoaneurysm or pulmonary infarct.

An intra-aortic counterpulsation balloon pump (IABP) is occasionally used in patients with cardiogenic shock. This catheter measures approximately 26 cm in length and is surrounded by a balloon, which inflates with helium or carbon dioxide gas during diastole and deflates during systole. Deflation during systole decreases afterload and results in diminished left ventricular work and oxygen requirements, while the inflation of the balloon during diastole increases cardiac pressure to help ensure adequate perfusion of the coronary arteries. The catheter, introduced percutaneously into the thoracic aorta via the common femoral artery or placed into the ascending aorta at the time of surgery, should be positioned so that its tip is just distal to the origin of the left subclavian artery. The tip of the catheter has a small radiopaque marker so that this position can be ascertained on the chest radiograph (Fig. 3–22). The major complications of the IAPB result from positioning of its tip proximal to the left subclavian artery, which may cause occlusion of the left subclavian vessel orifice, cerebral artery embolization, or aortic tear. If positioned too low, the balloon may occlude the celiac, superior mesenteric, and renal arteries.

The three major types of cardiac pacemakers are epicardial, subxiphoid, and transvenous. There is wide variation in their use in clinical practice today. Unipolar or bipolar pacemakers are most common and usually implanted in the chest wall with leads inserted into the subclavian vein. The unipolar pacemaker tip is normally situated at the apex of the right ventricle. The bipolar pacemaker has a proximal lead that terminates in the right atrium and a distal lead that terminates within the right ventricle (similar to the unipolar pacemaker position). Occasionally, a third lead will be present in the coronary sinus, appearing superior to the right ventricular lead (Fig. 3–23). Its posterior position can be confirmed on the lateral view. Transvenous placement of cardiac pacemakers carries the same potential complications, as does placement of any other catheter. The purpose of the chest radiograph after the pacemaker insertion is to document the appropriate placement of these leads, to check for complications from placement, and to establish a baseline examination to compare with future chest radiographs.

EXERCISE 3-1: INCREASED HEART SIZE

Clinical Histories:

Case 3-1. A 20-year-old uncooperative man with minimal chest pain (Fig. 3–24)

Case 3-2. A 70-year-old man with uremia (Fig. 3–25)

Case 3-3. A 60-year-old alcoholic man with shortness of breath (Fig. 3–26)

Case 3-4. A 28-year-old woman with a loud systolic murmur and without cyanosis (Fig. 3–27)

Case 3-5. A 55-year-old woman with an acute shortness of breath (Fig. 3–28A ); Fig. 3–28B obtained 1 month prior

Questions:

Radiologic Findings:

3-1. This case (Fig. 3–24) represents an apparent "enlarged heart" due to an expiratory phase of respiration in an uncooperative patient. (D is the correct answer to Question 3-1.) Note the decreased lung volumes and the elevation of the hemidiaphragms. The resultant crowding of vessels obscures much of the cardiac border. The technique of inspiratory PA and radiographs is preferred to avoid "diagnosing" diseases that a patient does not have.

3-2. This case (Fig. 3–25) is an example of pericardial effusion. (C is the correct answer to Question 3-2.) The conventional radiograph finding on the frontal view is a so-called "globular" or "water-bottle" configuration of the heart.

3-3. This case (Fig. 3–26) shows a radiographic finding similar to that of in Case 3-2. This is the case of cardiomyopathy. (C is the correct answer to Question 3-3.)

3-4. This patient (Fig. 3–27) has cardiomegaly, increased pulmonary vascularity, and prominent pulmonary arteries, findings suggestive of an intracardiac shunt, which in this case was an atrial septal defect (ASD). (C is the correct answer to Question 3-4.) The lateral radiograph (Fig. 3–29) shows the enlarged central pulmonary arteries and right ventricular prominence due to increased flow.

3-5. This case (Fig. 3–28A ) illustrates cardiomegaly, increased pulmonary vascularity, redistribution of blood flow to the upper lobes, and Kerley B lines typical of pulmonary edema. (B is the correct answer to Question 3-5.) Note the normal radiograph 1 month prior (Fig. 3–28B ).

Discussion:

Pericardial effusion and cardiomyopathy have similar appearances on PA chest radiographs (Cases 3-2 and 3-3). This appearance is often referred to as a globular shape or a water-bottle heart. When this appearance is observed, an echocardiogram is the next best imaging test to differentiate between these two entities. However, this diagnosis may be suggested on the lateral radiograph by a separation of the pericardial and epicardial fat by pericardial fluid, as exhibited in Fig. 3–25B (arrowheads). Mediastinal masses may occur in a location or a distribution that makes the heart appear enlarged on the chest radiograph. CT is the next best test to confirm a clinical suspicion of a mass and to evaluate mediastinal adenopathy.

Ebstein's anomaly, mentioned in Question 3-4, is an uncommon type of congenital heart disease that may also result in a globular-shaped appearance of the heart on the chest radiograph (Fig. 3–30). In these patients, the tricuspid valve is displaced downward, resulting in tricuspid regurgitation. There is usually an associated ASD. The tricuspid insufficiency results in a massively enlarged right atrium, and the pulmonary vascularity is usually diminished due to decreased flow through the pulmonary arteries. These patients often present with congestive failure early in life, and echocardiography, MR imaging, or cardiac angiography is necessary to make this diagnosis.

Increased heart size is a common clinical problem that may be caused by a variety of abnormalities. Cardiac enlargement may be diagnosed if the cardiothoracic ratio is greater than 60%. Often the lateral view is helpful for confirming left atrial and left ventricular enlargement. The most common cause of enlargement is atherosclerotic disease, although a number of other entities may cause an increased cardiac silhouette. In congestive heart failure (CHF) hydrostatic forces result in fluid collection in the interlobular septa, those connective tissue sheaths, veins, and lymphatics surrounding the secondary pulmonary lobule (Fig. 3–31, arrows). As hydrostatic pressures increase, fluid can accumulate in the alveoli, giving an air-space pattern of disease. Intracardiac shunts, especially ventricular septal defect, can also cause cardiac enlargement because of the increased flow from the internal shunting. VSD is the most common congenital cardiac anomaly, and the intracardiac shunt must be at least 2 to 1 for the radiograph to show recognizable changes.

EXERCISE 3-2: ALTERATIONS IN CARDIAC CONTOUR

Clinical Histories:

Case 3-6. A 65-year-old man with a long history of an abnormality seen on his electrocardiogram (Fig. 3–32)

Case 3-7. A 30-year-old woman with systolic and diastolic murmurs and a history of rheumatic fever as a child (Fig. 3–33) (Courtesy of Caroline Chiles, M.D., Winston-Salem, NC).

Case 3-8. A 75-year-old man with a history of a myocardial infarction 10 years earlier had this study done as a routine screening examination (Fig. 3–34)

Case 3-9. A 24-year-old man with recurrent pulmonary infections (Fig. 3–35)

Case 3-10. A 3-year-old child with a history of cardiac complications since birth (Fig. 3–36)

Questions:

Radiographic Findings:

3-6. In this case (Fig. 3–32), the classical findings of enlargement of the left ventricle, characteristic of left ventricular hypertrophy, are seen on both the PA and the lateral radiograph. Extensive aortic calcification and ectasia are also present. The most common cause of left ventricular hypertrophy is long-standing hypertension. (C is the correct answer to Question 3-6.)

3-7. In this case (Fig. 3–33), a double contour to the right side of the heart is seen on the PA radiograph (black arrow). There is also an enlarged left atrial appendage (white arrow). The lateral radiograph shows enlargement of the left atrial shadow, the superior and posterior region of the cardiac contour (arrows) and posterior displacement of the left main bronchus. (A is the correct answer to Question 3-7.) Along with increased pulmonary vascularity, the constellation of findings is characteristic of left atrial enlargement due to mitral valve insufficiency.

3-8. The PA and lateral radiographs in this case (Fig. 3–34) show an enlargement of the left ventricular contour with a focal bulge containing calcification within its wall (arrows). The lateral radiograph confirms the calcification (curved arrows). Given the history of myocardial infarction 10 years earlier, the most likely diagnosis is a left ventricular aneurysm. (D is the correct answer to Question 3-8.)

3-9. The patient in this case (Fig. 3–35) shows the apex of the heart to be on the right side of the chest and the descending aorta to be in its correct position on the left. These findings are diagnostic of dextrocardia, which in this case is secondary to Kartagener's syndrome. (B is the correct answer to Question 3-9.)

3-10. In this case (Fig. 3–36), tetralogy of Fallot, the apex of the left ventricle is elevated by right ventricular hypertrophy. These findings are sometimes referred to as a boot-shaped heart. (A is the correct answer to Question 3-10.)

Discussion:

Alterations of the normal cardiac contour are common clinical scenarios. The most common contour abnormality is probably enlargement of the left ventricle from long-standing hypertension, as exhibited by the 65-year-old man in Case 3-6 (Fig. 3–32). Cardiac enlargement is first suggested on the PA view by an increase in the CT ratio to greater than 50%. Left ventricular enlargement is suggested by prominence of the apex of the cardiac contour. On the lateral projection, the left ventricle should not project more than 2 cm posterior to the IVC measured 2 cm above the diaphragm. If the left ventricle projects more than 2 cm behind this landmark, left ventricular enlargement should be suspected.

Left atrial enlargement (LAE), as shown in Case 3-7 (Fig. 3–33), occurs mainly with left-sided obstructive lesions such as mitral stenosis or mitral regurgitation, often the result of rheumatic heart disease. The major sign of LAE on the PA view is a double density centrally caused by the dilated left atrium extending to the right of the spine projected behind the right atrium (Fig. 3–33A, black arrow). Another sign of LAE is enlargement of the left atrial appendage. The left atrial appendage is immediately adjacent and inferior to the left main bronchus. When enlarged, there is an extra bump along the left heart border, the so-called third mogul of the left cardiac border (Fig. 3–33A, white arrow ). LAE also causes a separation and widening of the carinal angle that can be seen on the PA chest radiograph, although this is a late sign of LAE. The carinal angle normally measures between 60 and 120 degrees. Widening of this angle may occasionally be caused by subcarinal adenopathy and therefore should be correlated with other signs of LAE.

The left atrium makes up the posterior cardiac shadow just above the left ventricle (LA in Fig. 3–1). Left atrial enlargement is recognized on the lateral film by enlargement and posterior displacement of the left atrial shadow (Fig. 3–33B, arrows ). As further enlargement occurs, the left atrium displaces the left main and left lower lobe bronchus posteriorly.

Right ventricular enlargement (RVE) or hypertrophy (RVH) results most commonly from right-sided heart failure from a variety of disorders, long-standing mitral disease, or pulmonic stenosis. In this cardiac contour abnormality, an increase occurs in the soft-tissue density within the retrosternal clear space that is best seen on the lateral radiograph (Fig. 3–37). On the PA film, uplifting of the cardiac apex may be seen also. Anterior mediastinal masses may also cause retrosternal fullness and should be included in the differential diagnosis (Fig. 3–38). When the cause is not clear from the conventional radiograph, CT is the next most appropriate test to differentiate between these two considerations.

Cardiac aneurysms, as shown in the patient in Case 3-8 (Fig. 3–34), are almost always the sequelae of myo-cardial infarction. There are two types of cardiac aneurysms: true and false aneurysms. True aneurysms most frequently occur at the cardiac apex and contain all three layers of myocardium. False aneurysms or pseudoaneurysms occur with disruption of the endocardium, with dissection of blood into the cardiac wall. Pseudoaneurysms, therefore, are not bound by all three layers of the heart wall. Pseudoaneurysms most frequently occur along the free walls of the heart (inferior and lateral walls). Aneurysms are usually diagnosed on the PA chest radiograph as localized soft-tissue outpouchings or irregularities at the apical or anterolateral segments of the left ventricular cardiac contour. A linear rim of dystrophic calcification may develop within the nonviable myocardium after the infarction. With echocardiography, aneurysms show paradoxical enlargement during systole. Because stasis of blood occurs in the aneurysm, blood clots can develop and may be a source of distal emboli. Echocardiography, CT and MR imaging can all be used to make the diagnosis of cardiac aneurysm and distinguish between true and false aneurysms. The distinction is important as false aneurysms are at higher risk for rupture and require surgical repair.

Dextrocardia, as shown in Case 3-9 (Fig. 3–35), is usually recognized easily on the PA chest radiograph. However, this finding may be overlooked if the left and right designations on the film are marked incorrectly or are misinterpreted. In most cases of dextrocardia, the aorta descends on the left side and the patient is asymptomatic. If the aorta descends on the right side, a number of other abnormalities should be considered (Table 3–5). The bibliography at the end of the chapter provides more in-depth discussion of this topic.

The boot shape of the cardiac shadow in Case 3-10 (Fig. 3–36) is secondary to tetralogy of Fallot. The four components of this congenital cardiac anomaly are an overriding aorta, ventricular septal defect, pulmonic stenosis, and right ventricular hypertrophy. It is the right heart enlargement that results in the upturned cardiac apex. The degree of shunt and pulmonary stenosis dictate the presentation. In cases where the stenosis is severe, infants are cyanotic and a generalized decrease in pulmonary vasculature is seen. If the pulmonary stenosis and degree of left to right shunt are mild, the abnormality may not manifest itself until childhood.

Total anomalous pulmonary venous return has been described as a snowman configuration. The right side of the snowman's head is formed by the dilated SVC, while the left side of the head is formed by the left anterior cardinal vein (vertical vein), draining all of the pulmonary veins to the left brachiocephalic vein. The body of the snowman is represented by the dilated right atrium and ventricle; the atrium bulges to the right and the ventricle expands to the left and superiorly, producing a convex cardiac border comprising the displaced left atrium and ventricle (Fig. 3–39).

EXERCISE 3-3: PULMONARY VASCULARITY

Clinical Histories:

Case 3-11. A 28-year-old man examined in the Emergency Department for chest pain and shortness of breath (Fig. 3–40)

Case 3-12. A 65-year-old woman with a 100-packs-a-year history of smoking (Fig. 3–41)

Case 3-13. An acyanotic 22-year-old man with a systolic murmur (Fig. 3–42)

Case 3-14. A 36-year-old man with asthma (Fig. 3–43)

Case 3-15. A 50-year-old woman with acute shortness of breath (Fig. 3–44)

Questions:

Radiologic Findings:

3-11.In this case (Fig. 3–40), the chest radiograph was normal in a 28-year-old man seen in the Emergency Department for chest pain. The electrocardiogram was also normal, and there was no obvious cause for the patient's pain. He had just stopped medication for a psychiatric illness and was hysterical. (D is the correct answer to Question 3-11.) Note the well-defined pulmonary vessels in the perihilar region and normal branching of these vessels into the lungs. There is a gradient of pulmonary vascular markings from the bases to the apices on an upright radiograph due to the increased perfusion to the lower lobes.

3-12. This case (Fig. 3–41) is an example of chronic obstructive pulmonary disease. The large central pulmonary arteries indicate pulmonary arterial hypertension. The curved arrow in Fig. 3–41A identifies the enlarged right descending pulmonary artery. (C is the correct answer to Question 3-12.) The generalized proximal pulmonary artery enlargement is confirmed on the lateral radiograph by the large left pulmonary artery (Fig. 3–41B, arrows ). Note the attenuation of vessels in the periphery of the lungs. This constellation of findings is typical of emphysema. There are also large bullae, which result in an absence of pulmonary vessels and hyperlucency of the lungs.

3-13. This case (Fig. 3–42) shows increased pulmonary vascularity in a 22-year-old patient with VSD. (C is the correct answer to Question 3-13.) Note the large central pulmonary arteries, the increased linear opacities radiating out into the lungs, and the relatively uniform distribution of the pulmonary vascular shadows. In individuals with long-standing intracardiac shunts and pulmonary hypertension, the pulmonary arterial resistance may exceed systemic pressures resulting in Eisenmenger's physiology, a reversal of an intracardiac shunt from L > R to R < L. In these individuals, the central pulmonary arteries are quite large, but the peripheral pulmonary arteries are markedly attenuated.

3-14. This case (Fig. 3–43) shows the characteristic appearance of venolobar (scimitar) syndrome. (B is the correct answer to Question 3-14.) The scimitar vein is the result of partial anomalous pulmonary venous return.

3-15. This case (Fig. 3–44) is an example of a long-standing hypertension in a patient with shortness of breath and pulmonary edema from congestive heart failure. (A is the correct answer to Question 3-15.) Note the increased size of the cardiac silhouette, the ill-defined reticular perihilar opacities, and the redistribution of blood flow to the upper lung zones. In this woman, the cause of the pulmonary edema was myocardial infarction.

Discussion:

The main pulmonary arteries are large, the lobar arteries smaller, and each branching segment becomes progressively smaller. On the chest radiograph, this pattern is manifested by linear opacities or shadows that are much more prominent in the central portion of the chest and gradually get less prominent toward the periphery of the lung, as in the normal person in Case 3-11. The right descending pulmonary artery (RDPA) is one important landmark on the PA chest film (see Fig. 3–1). In the normal chest, the lateral border of the RDPA is usually well demarcated, and the artery usually measures less than 15 mm at its widest diameter.

Enlargement of this vessel is caused by a variety of abnormalities (Table 3–6). Chronic obstructive pulmonary disease, with resultant pulmonary hypertension, is the most common cause of pulmonary arterial hypertension and is shown in the patient in Case 3-12 (Fig. 3–41).

Intracardiac shunts that result in increased pulmonary arterial flow can also enlarge the pulmonary vascular system. The most common lesions causing increased vascularity without cyanosis are ASD, VSD, and patent ductus arteriosus. Case 3-13 (Fig. 3–42) is an example of a VSD with increased vascularity. The main cardiac lesions with cyanosis and increased pulmonary vascularity are transposition of the great vessels, truncus arteriosus, and total anomalous pulmonary venous return. The standard texts listed in the bibliography at the end of the chapter provide in-depth discussions of these entities.

One other common cause of pulmonary artery enlargement is mitral disease (either stenosis or regurgitation). In this case, increasing left atrial pressures are transmitted to the pulmonary veins. In time, this raises pulmonary capillary wedge pressures and eventually right heart pressures, similar to cor pulmonale from left heart failure (see Case 3-7).

Venolobar syndrome is a form of partial anomalous pulmonary venous return. Note the right inferior pulmonary vein descending in a curvilinear fashion to empty into the inferior vena cava (Figs. 3–43 and 3–45). Right lung hypoplasia causes the small size of the right hemithorax and results in shift of the heart and mediastinum to the right. Other congenital anomalies may be present.

Pulmonary edema, as exhibited in Case 3-15 (Fig. 3–44), regardless of the cause, is another process that causes the increase in the pulmonary vascularity seen on chest radiograph (discussed further in the next chapter). Perihilar indistinctness, caused by interstitial edema, may obliterate the borders of the pulmonary vessels. Associated findings are redistribution of blood flow to the apices, Kerley B lines lines, and pleural effusions (Fig. 3–31).

EXERCISE 3-4: VASCULAR ABNORMALITIES

Clinical Histories:

Case 3-16. A 67-year-old man with a long history of hypertension (Fig. 3–46)

Case 3-17. A 25-year-old man with chest fullness (Fig. 3–47)

Case 3-18. A 76-year-old man with substernal chest pain (Fig. 3–48)

Case 3-19. A 22-year-old man with differential pulses in the legs and arms (Fig. 3–49)

Case 3-20. A 38-year-old man with a systolic murmur (Fig. 3–50) (Courtesy of Laurence B. Leinbach, M.D., Winston-Salem, NC.)

Questions:

Radiographic Findings:

3-16. In this case (Fig. 3–46), aortic ectasia (arrow) is seen in a patient who has had coronary artery bypass surgery and has a history of long-standing hypertension and aortic stenosis. (C is correct answer to Question 3-16.)

3-17. This case (Fig. 3–47) is an example of a right-sided aortic arch in an asymptomatic individual. (D is the correct answer to Question 3-17.)

3-18. This case (Fig. 3–48) is a radiograph of the patient in Case 3-16 (Fig. 3–46), 9 years later, and it shows a localized mass in the region of the ascending aorta. The CT image (Fig. 3–51) confirmed the large ascending aorta aneurysm. (E is the correct answer to Question 3-18.)

3-19. This case (Fig. 3–49) shows rib notching (arrowhead ) and a localized constriction of the proximal descending aorta (arrow). (B is the correct answer to Question 3-19.) These findings are diagnostic of coarctation of the aorta.

3-20. This case (Fig. 3–50) is an example of main pulmonary artery dilation (arrow) in a patient with pulmonic stenosis. (A is the correct answer to Question 3-20.)

Discussion:

Anomalies of the major vessels are commonly encountered on the chest radiograph. The aortic arch is an easily recognized shadow. On the PA projection, the aorta originates in the middle of the chest and then arches superiorly and slightly to the left (hence, the term aortic arch), then curves, crosses the mediastinum at an oblique angle, and continues as the descending thoracic aorta (see Fig. 3–1). The configuration of the aorta changes during life. In the young person, the aortic arch is narrow and smooth and the descending thoracic segment very straight. In the older individual with atherosclerotic disease or aortic stenosis, as shown in Case 3-16 (Fig. 3–46), the ascending aorta becomes more prominent along the right heart border and may have an undulating pattern in the descending thoracic portion.

Other abnormalities of the aortic arch are uncommon. Congenital aortic anomalies include left aortic arch with aberrant branching, right aortic arch, and double aortic arch. The most prominent of these aberrations is the right aortic arch, which occurs in 1 in 2500 people. It can be diagnosed on the conventional radiograph by noting an indentation to and slight deviation of the right side of the trachea and displacement of the SVC shadow, as shown in Case 3-17 (Fig. 3–47, arrows ). In many individuals, the right arch is discovered incidentally and, in these cases, is usually associated with an aberrant left subclavian artery (Fig. 3–52). The barium swallow can also demonstrate mass effect on the esophagus by the aberrant subclavian and aorta as it crosses from right to left in the chest. When associated with congenital anomalies (tetralogy of Fallot, truncus arteriosus, etc.), the great vessel branching pattern is a mirror image of that seen in a normal left aortic arch.

Aneurysms of the aorta, shown in Case 3-18 (Fig. 3–48), are most often caused by atherosclerosis. Trauma, infection, and connective tissue disorders such as Marfan's and Ehlers-Danlos syndrome are other causes. Aneurysms may be saccular or fusiform in shape, and symptoms include chest pain, hoarseness from compression of the recurrent laryngeal nerve, postobstructive atelectasis from compression of a bronchus, and dysphagia from esophageal compression. However, aneurysms are most commonly discovered as an incidental finding on an imaging study done for other reasons. An aneurysm of the ascending or transverse aortic segments shows a focal enlargement of the aortic shadow, usually with curvilinear calcification in its wall. A saccular aneurysm of the descending aorta may be misdiagnosed as a lung, mediastinal, or pleural mass, especially if it does not contain linear calcification. In these cases, as mentioned previously, CT is the next best imaging modality to perform (Fig. 3–51). The lack of rib destruction in Case 3-18 strongly argues against a chest wall sarcoma.

A special type of aneurysm is aortic dissection, which is usually caused by atherosclerosis with medial layer necrosis. In this disorder, blood dissects into the aortic wall through a tear of the intima. This process may begin anywhere along the course of the thoracic aorta, but the exact location is very important because it has therapeutic implications. Aortic dissection is most easily classified by the Stanford system. This divides dissections into type A, those involving the ascending aorta, and type B, those that begin distal to the left subclavian. When associated with symptoms, type A dissections are considered surgical emergencies, whereas symptomatic type B dissections often can be managed medically. In the acute setting, the diagnosis is best established by CT because it can rapidly define the entire scope of the dissection as well as show the relationship to other major vessels (Fig. 3–15). Echocardiography can also rapidly detect dissection but provides less anatomic detail. MR imaging is often not used in the acute setting due to time and availability issues. The role of angiography as a diagnostic procedure for dissection has virtually disappeared; however, intravascular therapy including placement of stent-grafts and fenestration of the dissection flap can be performed for treatment in many instances including individuals whose conditions are medically inoperable.

The abnormality in Case 3-19 (Fig. 3–49) is coarctation of the aorta. This congenital anomaly results in partial or complete obstruction of the aorta at the junction of the aortic arch and descending aorta near the ligamentum arteriosum (the in utero connection between the aorta and pulmonary arteries). About one-half of these individuals also have a bicuspid aortic valve. The obstruction to flow due to the coarctation results in elevated upper extremity blood pressure and decreased lower extremity blood pressure. A systolic ejection murmur may also be heard. Because of the partial aortic obstruction, collateral flow through the intercostal arteries results in the rib notching seen (Fig. 3–53).

EXERCISE 3-5: HEART AND GREAT VESSEL CALCIFICATIONS

Clinical Histories:

Case 3-21. A 75-year-old woman with "lots of murmurs" when examined by a medical student who was on the first day of clinical rotation (Fig. 3–54)

Case 3-22. A 70-year-old woman who told the medical student she had been very sick as a younger woman and did not know her diagnosis at that time (Fig. 3–55)

Case 3-23. A 65-year-old man with a long history of hypertension hospitalized 6 years ago with an acute illness; lateral chest radio-graph (Fig. 3–56)

Case 3-24. A 66-year-old man with long-standing diabetes mellitus; lateral chest radiograph (Fig. 3–57)

Case 3-25. A woman with shortness of breath and decreased exercise tolerance; PA and lateral chest radiographs (Fig. 3–58)

Questions:

Radiographic Findings:

3-21. The PA and lateral chest radiographs (Fig. 3–54) show irregular linear calcifications in two areas, best seen on the lateral projection. Anteriorly, the curved linear calcifications denoted by the straight arrow reside in the aortic valve. (C is the correct answer to Question 3-21.) The curved arrow posteriorly points to calcification within the mitral valve annulus. This woman had rheumatic fever as a young adult, and the calcifications in the aortic valve and mitral annulus resulted from this disease.

3-22. This case (Fig. 3–55) shows pericardial calcification in a woman who had viral pericarditis as a young child. (C is the correct answer to Question 3-22.) Note that the calcification is seen much better on the lateral view.

3-23. The lateral chest radiograph in this case (Fig. 3–56) shows linear calcification in a focal area overlying the left ventricle. This calcification resides in a left ventricular aneurysm that this man developed after a myo-cardial infarction 6 years earlier. (E is the correct answer to Question 3-23.)

3-24. The lateral chest radiograph in this case (Fig. 3–57) shows linear tram track calcifications overlying the course of the coronary arteries. These calcifications represent coronary artery atherosclerosis in a patient with long-standing diabetes. (D is the correct answer to Question 3-24.)

3-25. In this case (Fig. 3–58), a circular, heavily calcified area overlying the left atrium is seen in both the PA (arrowheads) and lateral (curved arrows) projections. These calcifications resided within a left atrial myxoma that was causing the patient's symptoms of shortness of breath and decreased exercise tolerance. (B is the correct answer to Question 3-25.)

Discussion:

Calcifications, present in almost any area of the cardiovascular system, may be either metastatic or dystrophic in origin. Metastatic calcifications are usually caused by soft-tissue deposition of calcium due to hypercalcemia of any cause. Dystrophic soft-tissue calcifications are responses to tissue injury or degeneration and have no metabolic cause. They can be seen in practically any of the soft-tissue components of the cardiovascular system. We will concentrate on calcifications that can be seen on the conventional radiograph, although CT is a more sensitive test for detecting calcium. Calcium scoring has become a popular way of assessing the degree of atherosclerosis in the coronary arteries, but provides mainly risk stratification rather than site-specific information of stenosis. The utility of this technique over traditional risk factors has yet to be proven. The most common site of calcification seen on the conventional chest radiograph is within the aorta, usually in elderly patients with long-standing atherosclerotic disease or diabetes. In this instance, the calcification is linear and is associated with the aortic wall (Fig. 3–32). These calcifications may also be present in aneurysms (Fig. 3–34).

The aortic valve and mitral valve annulus are the most common intracardiac regions to demonstrate dystrophic calcification, usually secondary to long-standing stenosis or insufficiency from rheumatic fever. Bicuspid valves may also show this type of calcification. The lateral film is best for deciding which valve is calcified. In Fig. 3–59, a line drawn from the hilum (C) obliquely and downward to intersect the anterior cardiophrenic angle (N) will project behind aortic calcifications (A). Calcifications that lie in back of this line are usually mitral annulus calcifications (M).

Pericardial calcification as in Case 3-22 (Fig. 3–55) is seen in approximately 50% of patients with constrictive pericarditis. It has a characteristic curvilinear appearance outlining the location of the pericardium and is most often seen along the right heart border (Fig. 3–55).

Myocardial calcification, as is seen in left ventricular aneurysms, was discussed in the exercise on altered cardiac contour, and is shown in a slightly different form in Case 3-23 (Fig. 3–56). Thin, focal, linear calcifications overlying the left ventricle should be considered as aneurysms, and echocardiography, CT, and MR imaging are all useful examinations to confirm this diagnosis.

Calcifications within the wall of the coronary arteries, as exhibited in Case 3-24 (Fig. 3–57), are recognized on conventional radiographs as thin, linear, calcific deposits corresponding to the course of the coronary arteries. When discovered by conventional radiographs, it is a late finding of atherosclerosis, and these patients have a high incidence of obstructive coronary artery disease.

Case 3-25 (Fig. 3–58) is an example of the rare primary cardiac neoplasm that may calcify and be detected initially on the plain film. The cardiac tumor that most commonly calcifies is the left atrial myxoma, and calcification occurs in about 10% of these lesions (Fig. 3–58). Rarely, myocardial metastatic disease (such as osteosarcoma) or other primary cardiac tumors may calcify. Finally, primary mediastinal neoplasms such as teratomas may rarely show calcification. In these patients, CT should be performed for diagnosis.

EXERCISE 3-6: MONITORING DEVICES

Clinical Histories:

Case 3-26. Routine supine portable chest radio-graph obtained after SG catheter placement (Fig. 3–60)

Case 3-27. Supine chest radiograph obtained after difficult CVP placement (Fig. 3–61) (Courtesy of Robert H. Choplin, M.D., Indianapolis, IN)

Case 3-28. Routine supine chest radiograph in ICU patient after placement of several lines and tubes (Fig. 3–62)

Case 3-29. Chest radiograph obtained following pacemaker insertion (Fig. 3–63)

Case 3-30. Chest radiograph obtained following central venous catheter placement (Fig. 3–64); history of prior surgery for congenital heart disease

Questions:

Radiographic Findings:

3-26. The supine portable chest radiograph obtained after SG catheter placement in this case (Fig. 3–60) is coiled within the right ventricle before it terminates in the proximal main pulmonary artery. (D is the correct answer to Question 3-26.) This coiling of the catheter in the right ventricle may cause thrombosis or arrhythmia, and it is necessary to reposition this catheter.

3-27. The supine chest radiograph in this case (Fig. 3–61) shows a pneumothorax after a difficult CVP placement. (Bis the correct answer to Question 3-27.) Pneumothorax is one of the potential complications of subclavian venous catheterization because the apex of the lung is approximately 5 mm below the subclavian vein.

3-28. In this case (Fig. 3–62), the chest radiograph obtained shows a nasogastric tube extending down the right main bronchus into the right lung (Fig. 3–62, arrow). (D is the correct answer to Question 3-28.)

3-29. In this case (Fig. 3–63), the tip of the right ventricular pacemaker lead extends lateral to the expected border of the myocardium. This positioning may cause the pacemaker to function poorly or cause pleural and/or pericardial effusion. Because the leads are introduced via the subclavian vein, pneumothorax is also a potential complication. (D is the correct answer to Question 3-29.) A CT confirmed the pacemaker lead perforation (Fig. 3–65).

3-30. The patient in this case (Fig. 3–64) had hypoplastic left heart syndrome as an infant. To correct this anomaly, numerous surgeries were performed to redirect blood in the setting of a single functional ventricle. As part of this procedure, the superior vena cava is directly anastamosed to the right pulmonary artery (Glenn procedure). (E is the correct answer to Question 3-30.) The inferior vena cava is also extended to the right pulmonary artery via a right atrial baffle (Fontan procedure) to complete the flow of deoxygenated blood from the body returning to the lungs. Blood returns from the lungs to the left atrium and finally to the dominant right ventricle via atrial and/or ventricular septal defects.

Discussion:

As mentioned in the subheading of monitoring devices within the chapter, a variety of catheters can be inserted into the heart and great vessels to monitor various hemodynamic parameters, particularly in the ICU setting. Table 3–3 lists the most common monitoring devices, and Table 3–4 shows the most common complications from placement of these devices. It is important to trace and account for each catheter individually. For instance, the nasogastric tube might have initially been mistaken for an EKG lead. The result of instilling fluid through this tube could have been disastrous. Even so, the result of this placement was a pneumothorax.

We have reviewed the normal placement of catheters and some of the more common related complications. The student should be familiar with this aspect of radiography in the ICU setting, and the references cited at the end of the chapter will provide further in-depth learning.

Chen JT, ed. Essentials of Cardiac Imaging. Philadelphia: Lippincott-Raven; 1997.

Elliott LP, ed. Cardiac Imaging in Infants, Children, and Adults. Philadelphia: Lippincott; 1991.

Higgins CB. Essentials of Cardiac Radiology and Imaging. Philadelphia: Lippincott; 1992.

Manning WJ, Pennell DJ, eds. Cardiovascular Magnetic Resonance. Philadelphia: Churchill-Livingstone; 2002.

Miller SW. Cardiac Radiology: The Requisites. St. Louis: Mosby; 1996.

Remy-Jardin J, ed. CT Angiography of the Chest. Philadelphia: Lippincott Williams & Wilkins; 2001.