Chapter 19. Cardiac Masses

Echocardiography is a powerful tool in the differential diagnosis of cardiac masses. Although echocardiography cannot replace pathologic examination in obtaining an exact diagnosis, characteristic features of the ultrasound images can help to differentiate these masses. Combining clinical data such as sex, age, signs of an extracardiac primary tumor, and response to therapy (anticoagulation or antibiotics) with morphologic properties, such as location, attachment site, size, mobility, texture, and number of tumors, often produces an accurate diagnosis. A correct diagnosis is crucial in therapeutic decision making, but because pathology specimens usually are obtained only during surgical resection, it is important to recognize the typical indirect and direct echocardiographic features of the various tumors. Echocardiography is the technique of choice; further, because of its close proximity to the heart, transesophageal echocardiography (TEE) in general is superior to transthoracic echocardiography (TTE).

Some normal structures may mimic cardiac masses: the eustachian (inferior caval vein) valve, the thebesian (coronary sinus) valve, a Chiari network, crista terminalis, pectinate muscles, atrial chords, a moderator band, trabeculations, ventricular noncompaction, the apical form of hypertrophic cardiomyopathy, and the ridge between the left upper pulmonary vein and left atrial appendage may all be misinterpreted as cardiac masses (see Chapter 3).1 With the development of three-dimensional real-time TEE, multislice imaging of cardiac masses is possible, allowing for better visualization of tumor morphology and location, which in turn may help to improve decision making during surgical resection.2 Real-time three-dimensional TEE may become the technique of choice for noninvasive evaluation of tumor size.3

Cardiac tumors may be primary or secondary and malignant or benign. Of all primary cardiac tumors 75% are benign and 25% are malignant. Of the benign tumors in McAllister and Fenoglio's observations of 533 primary tumors,4 24.4% were myxomas, 8.4% were lipomas, 7.9% were papillary fibroelastomas, and 6.8% were rhabdomyomas. Fibromas, hemangiomas, teratomas, atrioventricular nodal mesotheliomas, granular cell tumors, pericardial cysts, and bronchogenic cysts accounted for fewer than 5% each. In the malignant group, angiosarcoma (7.3%) and rhabdomyosarcoma (4.9%) were the most frequent, whereas mesothelioma, fibrosarcoma, malignant lymphoma, extraskeletal osteosarcoma, neurogenic sarcoma, malignant teratoma, thymoma, leiomyosarcoma, liposarcoma, and synovial sarcoma were rare conditions. Secondary tumors are more frequently carcinomas than sarcomas, but all types of tumors may be found.

Myxoma is the most frequent of the benign cardiac tumors, accounting for 30% to 50% and presenting with a female preponderance (Figure 19–1).5 They occur most often in the third through sixth decades, and more than 90% are sporadic. Left atrial localization is most frequent (75%),4,6,7 although 18% are found in the right atrium, 4% in the right ventricle, and another 4% in the left ventricle. Myxomas can present as multiple lesions in the left atrium and may be bilateral, whereas a ventricular location occurs more frequently in children. Myxomas typically are pedunculated, polypoid, friable tumors, sometimes possessing a smooth and rounded surface (Figure 19–2). They are commonly lobulated but can have a villous surface and typically are attached by a narrow stalk to the endocardial surface on the limbus of the left atrial side of the fossa ovalis. However, any other site of attachment is possible.4 Myxomas contain a mucopolysaccharide myxoid matrix and have a nonhomogeneous appearance on TEE because of the presence of channels, cystic areas, hemorrhage, or calcifications (Figure 19–3). A familial form of myxoma has been described with an autosomal dominant transmission.4 It occurs at a younger age, is seen more frequently in atypical locations, and is characterized by a higher recurrence rate after surgical resection.8,9 In contrast, the familial form has a male preponderance and is more frequently bilateral. Routine screening of first-degree relatives of patients with myxoma is therefore indicated, especially in young patients or if multiple tumors are found. Patients with a familial history of myxoma also should be screened carefully for multiple or atypically located myxomas, and repeated postoperative echocardiographic examinations are necessary to detect recurrence.10 This familial variety may be part of a syndrome (Carney's complex, NAME syndrome, or LAMB syndrome).11

A typical triad of symptoms includes embolization, obstruction, and constitutional symptoms such as dyspnea, position-related palpitations, syncope, congestive heart failure, and even sudden death. Emboli may cause neurologic deficit or coronary events, but any systemic vessel may be involved. Obstructive symptoms, detected as turbulence on color-flow Doppler, can present with any intracavitary tumor and may involve the mitral or tricuspid valve (atrial myxomas), pulmonic or aortic valve (ventricular myxoma), or venous inflow to the atria.12,13 If the mitral or tricuspid valve is obstructed, a typical tumor “plop” can be heard after the second heart sound on auscultation.

Except for detecting ventricular locations, TEE is superior to TTE. It allows for detailed description of tumor morphology and attachment, and for detection of multiple tumors. A bilateral dumbbell-shape myxoma may pass through the foramen ovale and may be fixed to the margin of this foramen.14 Right atrial myxomas tend to be more solid, have wider attachments, and may be fixed to the inferior rim of the fossa ovalis, the tricuspid valve, or the eustachian valve. Obstruction of the tricuspid valve or caval veins is possible.15,16 Left ventricular myxomas are rare, occur at younger age, and are three times more frequent in women than in men. In these cases, cerebral embolism is frequent and subaortic or aortic obstruction is possible. Right ventricular myxomas also are infrequent and may cause pulmonary embolism and outflow obstruction.

Rhabdomyoma is the most frequent cardiac tumor in infants and children and is associated with tuberous sclerosis.17,18 Of these, three-fourths occur before the age of 1 year. It is usually multiple and frequently involves the right ventricular myocardium. Occasionally, it may project into the ventricular cavity and even move freely as a pedunculated tumor.19 It can cause obstruction of the right ventricular outflow tract, and diagnosis by fetal echocardiography before birth is possible. Rhabdomyomas may regress spontaneously after birth.

Fibromas are ventricular intramural tumors that are frequently calcified. They occur more frequently in infants and children.20

Papillary fibroelastomas are small (usually <1 cm), homogeneous, mobile tumors, often with a stalk, originating from the cardiac valves or, less frequently, from the ventricular endocardium. Papillary fibroelastomas originate from the atrial side of the atrioventricular valves or from either side of the semilunar valves and frequently are a coincidental finding. The most common locations are on the aortic valve cusps (44.5%) and mitral valve leaflets (36.4%). Attachment to the ventricular septum or close to the left ventricular outflow tract or to the subvalvular mitral apparatus has been described (Figure 19–4). They can cause angina and infarction by coronary ostial occlusion or embolism,21,22 but systemic embolism is also possible so surgical resection is advocated. They occur most commonly in patients older than 50 years but rarely occur on the right side of the heart.17,23,24 Multiple fibroelastomas occur in 6.8% to 7.5% of cases.25 Fibroelastomas have a short pedicle with multiple papillary fronds, and have to be differentiated from Lambl excrescences, which are degenerative in origin and arise from the ventricular side of the semilunar valves along the coaptation line (Figure 19–5).17 The exact histogenesis of papillary fibroelastoma is uncertain, and although most investigators classify it as a neoplasm, it may represent exuberant organization of thrombi, similar to Lambl excrescences.25 Colocalization of Lambl excrescences and fibroelastomas suggest a common origin. A virus-induced tumor hypothesis also has been proposed. Differential diagnosis from endocarditis and vegetations may be difficult and depends on the clinical presentation of the patient. However, in contrast to endocarditis, valvular dysfunction (insufficiency) is uncommon.

Lipomas affect the entire heart and pericardium and can be massive.26 They may produce a pericardial effusion. Intramyocardial lipomas are well encapsulated and small.17 Occasionally, a lipoma may arise from the mitral or tricuspid valve, and differential diagnosis with a myxoma becomes necessary.27

Lipomatous hypertrophy of the interatrial septum is a form of hyperplasia of adipose tissue (Figure 19–6). It presents as atrial septal thickening with a bilobed or “dumbbell” appearance due to sparing of the fossa ovalis.

Most malignant primary cardiac tumors are sarcomas, most frequently angiosarcomas originating in the right atrium or pericardium.28,29 They demonstrate a male preponderance. Angiosarcomas often (25%) grow partially intracavitary and may cause caval or valvular obstruction.30 Cardiac rupture,6 right heart failure, and pericardial tamponade have been described.

Rhabdomyosarcoma is the second most frequent primary cardiac sarcoma. It is also more frequent in males, has no predilection for any cardiac chamber, is often multiple, and frequently causes obstruction of at least one valve.31

Liposarcoma, fibrosarcoma, primary malignant lymphoma, and sarcomas of other cell lines are rare. Any of these also can cause obstruction or result in peripheral embolism.

Pericardial cysts are the most frequent tumors of the pericardium. They are benign, occur most often in the third and fourth decades of life, and are as frequent in men as in women. They appear as fluid-filled, well-delineated, more or less rounded structures. A frequent location is the right costophrenic angle,32 and rare cases of cardiac-chamber compression have been described.33

Echinococcus cysts, caused by a parasite endemic to Greece and Turkey, can involve the left ventricular free wall, the interventricular septum, the right ventricle, and the pericardium. They are usually septated and can calcify.

Blood cysts are found on the closure lines of the valvular endocardium. They are well-circumscribed masses with thin walls and echolucent core. They are presumed to be of congenital origin.1Teratomas occur most frequently in infants and children, with a female preponderance.17 They are benign tumors with an extracardiac but intrapericardial location in most cases, and are noted for containing hair, teeth, or other epidermal structures. Blood supply for these tumors arises from the aortic root or pulmonary artery via vasa vasorum. Recurrent, nonbloody pericardial effusion in a child is highly suggestive of pericardial teratoma.

Mesotheliomas are the third most frequent malignant primary tumors of the heart and pericardium.4 The highest incidence occurs in the third to fifth decades of life, with men being affected twice as often as women. Their symptomatology is similar to those of pericarditis, constrictive pericardial disease, and caval obstruction.

Aortic tumors are rare and most frequently are malignant sarcomas. These may involve any segment of the aorta and cause symptoms similar to those of aortic dissection and atherosclerotic occlusive disease. Peripheral metastases are common.

Metastases may involve the heart, the pericardium, myocardium, endocardium, valves, and coronary arteries. Direct invasion through caval or pulmonary veins is also possible. They occur more frequently in people older than 50 years and affect men and women with similar frequency. Metastatic carcinomas are more frequent than sarcomas, but all types of primary tumors may metastasize to the heart, and metastases are, most often, multiple. Malignant melanoma has a tendency to spread to the heart in more than 50% of cases,33 but cardiac metastases most frequently originate from the more common bronchogenic and breast carcinomas (lung > breast).6 If the pericardium is involved, they can cause pericardial fluid accumulation and symptoms of pericarditis or tamponade with typical diastolic collapse of the right atrium and ventricle, inferior caval vein distention, and blunting of the normal inspiratory response. Direct myocardial involvement can result in extrasystolic beats, conduction disturbances, and arrhythmias resistant to therapy.34 If coronary arteries are affected, myocardial ischemia or infarction may result. There also may be external compression, tumor embolization, concomitant coronary atherosclerosis, or fibrosis due to radiation therapy.35 Renal cell carcinoma, hepatocellular carcinoma, and uterine leiomyomatosis may extend along the inferior caval vein toward the right atrium and cause venous inflow and even valvular obstruction (Figure 19–7).

Leukemic myocardial infiltration may cause congestive heart failure, mitral valve dysfunction, myocardial rupture, or pericardial effusion and tamponade.6,35

Malignant lymphomas frequently involve the heart but this is rarely discovered before death. Hodgkin's and non-Hodgkin's lymphomas can metastasize to the heart through the blood or lymph, or they can invade the heart directly from another intrathoracic location. In most cases, the epicardium and pericardium are affected.

Carcinoid tumors are never primary cardiac tumors and only rarely metastasize to the heart. Most frequently, the tumor resides in the gastrointestinal tract (ileum) and causes carcinoid disease of the heart by the release of products such as serotonin, 5-hydroxytryptamine, and bradykinin into the venous blood.36-39 Only patients with liver metastases develop cardiac lesions. The right heart is affected more commonly than the left heart, but bronchial carcinoid tumors are more likely to result in carcinoid disease of the left heart. The presence of an interatrial connection or massive right heart involvement also may cause left heart contamination. Carcinoid disease produces deposits on pulmonary and tricuspid valves and on right atrial and ventricular endocardia. Regurgitation and stenosis of pulmonary and tricuspid valves may arise, and the endocardial involvement causes a restrictive myopathy. Echocardiography typically shows right ventricular volume overload and pulmonary and tricuspid abnormalities. The tricuspid valve appears thickened, retracted, and fixed in a semi-open position with diastolic doming if stenosis is predominant, but most often tricuspid regurgitation is present. Pulmonary valve abnormalities occur in more than 50% of patients with predominant stenosis. Mitral involvement is rare, but, if the mitral valve is affected, insufficiency and stenosis are also possible.

Intracardiac thrombi may mimic cardiac tumors. Left atrial thrombi most often appear in the left atrial appendage in patients with atrial fibrillation, rheumatic mitral stenosis, left atrial enlargement, prosthetic mitral valve disease, and low cardiac output. Right atrial thrombi can obstruct the tricuspid valve or cause pulmonary embolism or paradoxical embolism via a patent foramen ovale (PFO). Pacemaker wires, central venous catheters, or pulmonary artery catheters increase the risk for thrombus formation. TEE is superior to TTE to describe thrombus size, mobility, attachment site, and involvement of superior or inferior caval veins; to detect entrapment by eustachian valve (Figure 19–8) or Chiari network; to search for extension to the left atrium via a patent foramen ovale, extension to the right ventricle, or the pulmonary artery; and to differentiate them from atrial myxoma.40-44 Thrombi typically appear as coiled, mobile, serpiginous masses with no clear point of attachment, but sometimes present as a more sessile mass. They can be fixed to the lateral atrial wall, inferior or superior vena cava, interatrial septum, eustachian valve, or Chiari network. Thrombolytic or anticoagulant therapy is indicated when intracardiac thrombi are detected. Disappearance of these masses with therapy confirms the diagnosis and illustrates the need for repeated echocardiographic examination. TEE examination before cardioversion for atrial fibrillation is essential to prevent thromboembolic complications.

Ventricular thrombi occur in patients with large myocardial infarction, ventricular aneurysm, and dilated cardiomyopathy, or in patients with the hypereosinophilic syndrome. Most thrombi reside in the apex of the left ventricle and may be isolated, multiple, laminar, spherical, pedunculated and mobile, or filamentous with a fixed base (Figures 19–9 and 19–10). They are often homogeneous and smooth but may be cavitary and heterogeneous (Figure 19–11). Mobile thrombi with shaggy, irregular borders in patients with ventricular aneurysm or dilated cardiomyopathy have been associated with an increased risk for embolization. The use of contrast echocardiography has been advocated recently as a technique for successful differentiation between a thrombus and a cardiac mass. In contradistinction to the filling defect seen with a thrombus, significant uptake of contrast agent into the mass confirms the diagnosis of a cardiac tumor. TTE or epicardial echocardiography may be superior to TEE for identification of left ventricular apical thrombi.45 Some authors describe an entity called “calcified amorphous tumor of the heart” (CAT). CATs are poorly characterized nonneoplastic, endocardially based intracavitary cardiac masses.46

An atrial septal aneurysm is a rare condition (0.22% to 1% of adults) defined as an aneurysmal bulging of the interatrial septum, most often at the level of the fossa ovalis. The septum is described as aneurysmal if it has a base wider than 15 mm and the phasic left-to-right excursion during the cardiac cycle is longer than 15 mm (Figure 19–12). Aneurysmal excursion can be best recorded on an M-mode echocardiogram on the bicaval view with TEE. This lesion is associated with atrial septal defects (often multiple) and commonly a patent foramen ovale, and with mitral valve prolapse.47–50 TEE is most sensitive to detect, describe, and differentiate this abnormality. Atrial septal aneurysm is not a neoplastic disease but causes its morbidity and mortality by thromboembolic mechanisms. Spontaneous contrast and thrombus entrapment have been described in the aneurysmal pocket and may necessitate differentiation from a cardiac tumor. The presence of atrial septal aneurysm has been associated with a PFO and higher incidences of cryptogenic51 and recurrent52 strokes.

Endocarditis also may result in cardiac masses. Vegetations differ from thrombi and tumors in several morphologic characteristics. Vegetations occur often in patients with normal ventricular function; they move in phase with valve motion because they are attached to valvular structures; and they are associated with valvular regurgitation, flail leaflets, ring abscesses, sinus of Valsalva aneurysms, paravalvular leaks, and clinical sepsis. Vegetations most frequently originate from the atrial side of the atrioventricular valves (Figure 19–13) and from the ventricular side of the aortic or pulmonic valve. They can be mobile, irregularly shaped, and heterogeneous, and are prone to embolization. For the diagnosis and fine description of endocarditis, TEE is superior to TTE. TEE is also very accurate in detecting complications of endocarditis and for monitoring therapy. Vegetations can change in size or, ideally, disappear after weeks to months of antibiotic therapy; thus, repeated echocardiography is essential.