Evaluation of Intracardiac Masses

Intracardiac Masses: Generalities

The differential diagnosis of an intracardiac mass includes thrombus, vegetation, tumor, iatrogenic material, extracardiac tissue, and normal variant. Narrowing the diagnosis down by 2DE and then 3DE should be and is the goal of imaging. As mentioned, tissue characterization remains the holy grail of imaging and, as such, remains challenging. However, characteristics such as inhomogeneity suggest tumor, whereas a highly homogeneous sessile mass is more characteristic of a thrombus. However, clot lysis does exist, presenting a highly inhomogeneous look, and thrombi can be quite mobile. A clear stalk has been believed to suggest tumor, but thrombi occasionally are attached to clear stalks as well. Further details are provided with each individual discussion of masses that follows.

Tumors: Generalities

Primary tumors of the heart are extremely rare, with a reported prevalence of 0.001% to 0.03% by autopsy series. The most common primary cardiac tumor is the myxoma, even though myxoma is relatively uncommon. Myxomas are most common in the atria, particularly the left atrium. They often have a clear stalk attached to the interatrial septum and clearly visualized with 3DE. Myxomas typically are benign, but the most common primary malignant tumors are sarcomas, which are highly invasive and uniformly fatal tumors. Angiosarcoma is the most common of this group. Metastatic tumors to the heart are much more common than are primary tumors, with the most common being breast and lung tumors; the usual cardiac site of metastasis is the pericardium. In fact, secondary involvement of the heart by extracardiac tumors is 20 to 40 times more common compared with primary cardiac tumors. Melanoma is a tumor that has particular propensity to metastasize to the heart.

Individual Tumors: Myxomas

As mentioned, myxomas are the most common primary cardiac tumors ( Figures 16-1 to 16-3 ; Videos 16-1 to 16-6 ). 3D imaging of atrial myxomas has been reported by transthoracic and transesophageal methods. The main benefits of 3DE over 2DE for myxomas are (1) identification of the stalk of the tumor and (2) evaluation of the heterogeneity of the mass. In fact, both characteristics often are seen with 2DE. The first case of imaging a right atrial myxoma by RT3DTEE was reported by Scohy et al ( Figure 16-4 ). At the time of surgical excision, it was noted that the size of the mass correlated extremely well with the estimate by RT3DTEE. In fact, the volume of 6.4 mL was the same as shown by 3DTEE and by ex vivo measurement. Butz et al also measured a left atrial myxoma preoperatively by using 3DTEE and determined excellent correlation with the excised mass at the time of surgery. In another case study, a right ventricular and tricuspid valve myxoma was identified by 2DTTE; it measured 5.5 × 3.8 cm but was remarkably larger as shown by 3DTTE (12 × 6 cm). 3DTTE improved the visualization of the special relationship with surrounding structures and identified the involvement of the tricuspid valve, which was not appreciated by 2DTTE ( Figure 16-5 ). Two cases of giant myxoma resulting in significant mitral valve obstruction were described by Culp et al. RT3DTEE volume measurement coordinated well with the ex vivo measurement. 2DTEE underestimated the volume ( Figure 16-6 ).

Prior to these publications, incremental value for the characterization of internal composition of masses and volume calculation had been appreciated with RT3DTTE imaging for myxomas and a hemangioma. In this small series, four left atrial tumors, including three myxomas and one hemangioma, were imaged by RT3D and correlated with histopathology specimens. Echolucencies suggestive of intramass hemorrhage were more frequently seen with 3D imaging compared with 2DE. In addition, 3DTTE detected more extensive and closely packed echolucencies involving the whole extent of the tumor in the hemangioma compared with more scattered echolucencies in myxomas ( Figure 16-7 ).

Fibroma

Fibroma is a congenital neoplasm that usually affects children. A right ventricular fibroma was diagnosed by 2DTTE in a patient with previous incomplete resection of the same. The fibroma ( Figure 16-8 ) was dramatically larger (9.0 × 2.8 cm) by RT3DTTE compared with 2DE (2.6 × 2.7 cm). A left atrial fibroma ( Figure 16-9 ) was associated with Gardner syndrome.