Cardiac Masses and Embolic Sources

Farid Jadbabaie

TRANSESOPHAGEAL ECHOCARDIOGRAPHY (TEE) IS AN extremely useful imaging modality for the assessment of cardiac masses and sources of emboli. Enhanced resolution of TEE and proximity of the transducer to posterior cardiac structures enable visualization of small masses or thrombi in the left atrium or the left atrial appendage (LAA) that would otherwise be missed on transthoracic echocardiography. Moreover, additional techniques such as contrast echocardiography and three-dimensional (3D) imaging can provide further information on vascularity of the mass and its spatial relationship to neighboring cardiac structures. In evaluation of cardiac masses, it is essential to identify normal cardiac structures and recognize image artifacts that can be mistaken for a cardiac mass or thrombus (1,2). Normal structures such as pectinate muscle in the LAA or the tissue fold between LAA and left upper pulmonary vein (Coumadin ridge) can be mistaken for a thrombus or a small tumor (Fig. 20.1). Similarly, a prominent Chiari network in the right atrium can be mistaken for a right atrial mass.

CARDIAC TUMORS

Primary cardiac tumors are very rare and account for 25% of all cardiac neoplasms in pathologic studies (3). Majority of primary cardiac tumors are benign without local invasion or metastatic spread. In contrast, malignant tumors often appear as large masses with invasion into the surrounding cardiac structures.

Myxoma

Myxoma is the most common primary cardiac tumor in adults and accounts for 30% of all primary cardiac neoplasms. Cardiac myxomas commonly arise from the left atrium but can also originate from the right atrium or the ventricles. These tumors are usually pedunculated and have a smooth surface. The most common attachment site is the fossa ovalis on the left side of the atrial septum. Myxoma is a slow-growing tumor and can remain asymptomatic for a long period of time. If undetected, myxomas can grow in size and occupy a significant portion of the left atrium, causing obstruction of the flow across the mitral valve (Fig. 20.2, Videos 20.1, 20.2). Cardiac myxomas are friable and can often result in systemic embolization.

Lipoma

Lipomas are the second most common cardiac tumors in adults and account for 10% of all benign cardiac neoplasms (3). These tumors usually originate from ventricular myocardium and less commonly from atrial myocardium. These tumors are often sessile with increased echogenicity and have a smooth surface. Lipomas are slow-growing tumors and can become large and cause blood flow obstruction (Fig. 20.3, Video 20.3). Cardiac lipomas should be distinguished from lipomatous hypertrophy of interatrial septum, which is hallmarked by the infiltration of mature fat cells and a characteristic appearance of the dumbbell-shaped thickening of atrial septum with the sparing of fossa ovalis (4) (Fig. 20.4, Video 20.4). Lipomatous hypertrophy is more commonly seen in older adults, especially older women, and usually has a benign clinical course.

Papillary Fibroelastoma

Papillary fibroelastoma is the third most common primary cardiac tumor in adults. Fibroelastomas are small mobile tumors that commonly originate from the valvular leaflets but can also arise from other endocardial surfaces. Aortic valve is the most common site of origin followed by the mitral valve. These tumors often appear as a small (0.5 to 2 cm) pedunculated echo density, with multiple mobile fibrillar projections, that is attached to the valve leaflets (5–7) (Fig. 20.5, Video 20.5). Fibroblastomas have a high potential for embolization, which is thought to be from the embolization of tumor fragments or associated thrombi. Risk of embolization is higher as the tumor grows larger. Valvular fibroelastomas are frequently confused with vegetations given the size, location, and potential for embolization. In contrast to vegetations, fibroelastomas mostly arise from the aortic side of the aortic valve leaflets (5,6) and are not associated with significant valvular abnormalities (7). Prominent valvular (Lambl’s) excrescences are the other condition that can also be confused with fibroelastomas (6). Valvular excrescences are commonly seen on commissural edges of the valve leaflets and comprise a small fibrous core covered by endothelial cells. These densities are commonly seen on TEE in all groups and are not associated with embolic events (8). An example of a prominent Lambl’s excrescence on the aortic valve is shown in Figure 20.6, (Video 20.6).

Rhabdomyoma

Rhabdomyomas are the most common primary cardiac tumor in children (2,3). Rhabdomyomas are almost always associated with tuberous sclerosis. They usually originate from either ventricle and are often multiple. These tumors can become large and cause valvular or outflow tract obstruction. Asymptomatic rhabdomyomas are usually followed over time, as some of these tumors can spontaneously resolve.

Fibroma

Fibromas are the second most common benign cardiac tumor in children. Fibromas usually originate from the ventricles or the atrioventricular grove. A characteristic feature of fibromas is the presence of central calcification. Fibromas usually appear as a large single intramural mass with multiple central densities. Singularity and presence of central calcification are key factors in differentiating fibromas from rhabdomyomas (Fig. 20.7).

Cardiac Sarcomas

Malignant tumors such as sarcomas are rare causes of cardiac tumors and usually originate from the ventricular myocardium. These tumors can become large and invade into any cavity and surrounding structures with protruding mobile components and an attached thrombus (Fig. 20.8). One of the distinguishing features of malignant cardiac tumors is enhancement with ultrasound contrast given their extensive vascularity.

Metastatic Tumors

Metastatic tumors involve the heart or the pericardium through local invasion (such as breast or lung Ca) or hematogenous spread (melanoma). Tumors that invade the heart locally can at times be seen on TEE as an external mass compressing or invading the cardiac chambers (Fig. 20.9, Video 20.7).

Embolization

Most cardiac tumors have the potential for embolization. Emboli can be from tumor fragments or dissociation of attached thrombi. Certain tumors, such as fibroelastoma and myxoma, are associated with higher rates of embolization. In one study, 30% of patients with an incidental finding of fibroelastoma had symptoms consistent with systemic embolization on clinical follow-up (5). In rare instances, large tumor fragments from distant sites can be seen in transit through the inferior vena cava and the right heart. Renal cell carcinoma is commonly associated with embolization and transit of tumor fragments through the right heart.

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