Cardiac Masses and Embolic Sources



Cardiac Masses and Embolic Sources


Farid Jadbabaie



INTRODUCTION

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 atria, atrial appendages or attached to cardiac valves or devices 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 the 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 left atrial appendage (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 (3,4). 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.






FIGURE 20.1 Normal cardiac structures can often be mistaken for cardiac masses or thrombus. Panel A shows a prominent pectinate muscle in the left atrial appendage mimicking a thrombus. An example of a prominent Coumadin ridge is shown in panel B and an example of a prominent Chiari network is shown in panel C. LAA, left atrial appendage; LA, left atrium; PV, pulmonary vein; LV, left ventricle; RA, right atrium; asterisk, shows the posterior horn of LAA.







FIGURE 20.2 Example of a large myxoma in the left atrium (asterisk) with a stalk (arrow) attached to the atrial septum (panel A). Tumor prolapses into the left ventricle during diastole (panel B). LA, left atrium; RA, right atrium; SVC, superior vena cava.


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; image Videos 20.1 and 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 often appear as a sessile mass with smooth surface and increased echogenicity. Lipomas are slow-growing tumors that can become large and cause obstruction to blood flow (Fig. 20.3; image 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 dumbbellshaped thickening of atrial septum with the sparing of fossa ovalis (5) (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.






FIGURE 20.3 Example of a large lipoma (asterisk) involving the interatrial septum. Note the echogenicity of the tumor and acoustic shadowing. LA, left atrium; IVC, inferior vena cava; RA, right atrium; SVC, superior vena cava.






FIGURE 20.4 Example of lipomatous hypertrophy of interatrial septum (asterisks) is depicted. Note the characteristic “dumbbell-shape” appearance and sparing of fossa ovalis. LA, left atrium; RA, right atrium; SVC, superior vena cava.


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 (6,7,8) (Fig. 20.5; image Videos 20.5 to 20.7). 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 (6,7,8) and are not associated with significant
valvular abnormalities (8). Prominent valvular (Lambl) excrescences are other conditions 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 age groups and are not associated with embolic events (9). An example of a prominent Lambl excrescence on the aortic valve is shown in (Fig. 20.6; image Video 20.8).






FIGURE 20.5 A: Example of a papillary fibroelastoma on mitral valve (arrow). B: Surgeon’s view 3D image of same tumor (arrow). LA, left atrium; LV, left ventricle; LAA, left atrial appendage; AoV, aortic valve; AML, anterior mitral leaflet; PML, posterior mitral leaflet.






FIGURE 20.6 Example of a Lambl excrescence on the aortic valve leaflets (arrow).


Rhabdomyoma

Rhabdomyomas are the most common primary cardiac tumor in children (2,3). Rhabdomyomas are almost always associated with tuberous sclerosis. They often appear as multiple tumors originating from the left or right ventricular myocardium. 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 tumors in children (2,3). Fibromas usually originate from the ventricles or the atrioventricular grove. A characteristic feature of fibroma 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 neoplasms 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 attached thrombi (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; image Video 20.9).


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 (6). In rare instances, large tumor fragments from distant sites can be seen in transit through the inferior vena cava (IVC) and the right heart. Renal cell carcinoma is commonly associated with embolization and transit of tumor fragments through the right heart (Fig. 20.10; image Video 20.10).






FIGURE 20.7 Example of a fibroma involving the medial left atrial wall and the atrial septum (arrow). LA, left atrium; SVC, superior vena cava; RA, right atrium.






FIGURE 20.8 Mid-esophageal bicaval view of an angiosarcoma of the right atrium. In this image, a large mass is occupying the entire right atrium (panel A). Tumor fragments (asterisks) prolapse across the tricuspid valve (arrowheads) into the right ventricle and right ventricular outflow tract (panel B). LA, left atrium; RA, right atrium; SVC, superior vena cava; RVOT, right ventricular outflow tract.






FIGURE 20.9 Example of a large extracardiac tumor manifesting as a heterogeneous mass anterior to the superior vena cava. RA, right atrium; LA, left atrium; SVC, superior vena cava; RV, right ventricle.






FIGURE 20.10 Example of a tumor fragment emboli in transit through inferior vena cava (IVC) in the right atrium (RA) in a patient with renal cell carcinoma (asterisk). RA, right atrium; LA, left atrium; SVC, superior vena cava; IVC, inferior vena cava.


INTRACARDIAC THROMBUS

Thrombi can be formed within any cardiac chamber and are mostly associated with an underlying wall motion abnormality or low-flow state leading to stasis of blood. The most common sites for intracardiac thrombus are the LAA and the left atrium commonly seen in patients with atrial fibrillation or rheumatic mitral disease (Fig. 20.11; image Videos 20.11 and 20.12). Thrombus can also be formed on intracardiac devices such as pacemaker wires or septal closure devices or be attached to indwelling catheters in the right heart (Fig. 20.12; image Video 20.13). Thrombus in the ventricles is almost always associated with an underlying wall
motion abnormality. Fresh thrombi tend to be round and mobile, whereas chronic thrombi appear flat and laminated and are less mobile. Size and mobility are important predictors of systemic embolization (Fig. 20.13; image Video 20.14).

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Apr 16, 2020 | Posted by in ANESTHESIA | Comments Off on Cardiac Masses and Embolic Sources
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