Chapter 16 Evaluation of Intracardiac Masses

Introduction

Perhaps no finding on echocardiography creates a bigger diagnostic challenge than the presence of an intracardiac mass. This is because tissue characterization by any imaging modality is limited. The advent of tomographic imaging in general, including computed tomography (CT), magnetic resonance imaging, and echocardiography, has dramatically improved the detection of intracardiac masses, but mass characterization remains challenging. The diagnosis of some masses, particularly thrombi, can be reasonably certain on the basis of the company that they keep, such as the association of thrombi and regional wall motion abnormalities. Likewise, papillary fibroelastomas are classically seen on the ventricular side of the semilunar valves, and atrial myxomas frequently attach to the interatrial septum. Angiosarcomas typically originate from a vascular structure, particularly the inferior or superior vena cava.

Beyond these generalities, additional deductive reasoning is limited when it comes to the diagnosis of an intracardiac mass. Although real-time three-dimensional echocardiography (RT3DE) can add some information about the tissue characterization of cardiac masses, its true strengths are accurate assessment of size and volume of the mass as well as the relationship of the mass to adjacent cardiac structures. Both RT3D transthoracic echocardiography (TTE) and more recently RT3D transesophageal echocardiography (TEE) have been extensively used, even within the brief time of their existence, for imaging cardiac masses.

Types of Real-Time Three-Dimensional Echocardiography Imaging

3DE imaging took a major step in 2002, when previous gated methods of 3DE acquisition were replaced with RT3DTTE. In 2007, RT3DTEE imaging became available, revolutionizing the evaluation of intracardiac masses.

General Benefits of Three-Dimensional Echocardiography Over Two-Dimensional Echocardiography

The potential and realized benefits of 3DE for mass evaluation include (1) improved spatial relationships to adjacent anatomic structures; (2) improved accuracy of size and volume of the masses; (3) improved detail of the homogeneity (or lack thereof) of the mass using the cropping function of 3D software; (4) involvement or noninvolvement of adjacent structures, such as interatrial or interventricular septum, valves, or myocardium; and (5) mobility in 3D space and, as a correlate, identification of the stalk of the mass, if present.

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.¹ 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.¹^–³ Melanoma is a tumor that has particular propensity to metastasize to the heart.⁴

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).⁵ 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 al⁶ 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).⁷ Two cases of giant myxoma resulting in significant mitral valve obstruction were described by Culp et al.⁸ RT3DTEE volume measurement coordinated well with the ex vivo measurement. 2DTEE underestimated the volume (Figure 16-6).

Figure 16-1 Left atrial myxoma imaging with two-dimensional echocardiography (A) and three-dimensional echocardiography (B) in the short-axis view (see Videos 16-1 and 16-2).

Figure 16-2 A, Zoom of two-dimensional echocardiography view of left atrial myxoma showing the attachment point of the mass to the left atrial wall (B). Note the attachment point to the left atrial wall has a close relationship to the anterior leaflet of the mitral valve and the posterior portion of the aortic annulus (see Video 16-3).

Figure 16-3 Two-dimensional (2D) (A) and three-dimensional (3D) echocardiography (B) of the apical four-chamber view of left atrial myxoma. The volume perspective and size are appreciated in the 3D view. Note that in these particular views, the stalk of the mass, attached to the interatrial septum, is more easily visualized in the 2D image, although cropping of the 3D image was possible and identified the stalk (see Videos 16-4 to 16-6).

Figure 16-4 Volume rendering of the right atrial mass offline by TomTec (Munich, Germany) four-dimensional imaging showing that volume measurement can be performed. The result was 6.36 mL, comparable with the in vitro measurement of 6.4 mL.

(From Scohy TV, Lecomte PV, McGhie J, et al: Intraoperative real time three-dimensional transesophageal echocardiographic evaluation of right atrial tumor. Echocardiography 25:646–649, 2008.)

Figure 16-5 A and B, A right ventricular myxoma with involvement of the tricuspid valve. The tricuspid valve involvement was not appreciated by two-dimensional echocardiography. LV, left ventricle; RA, right atrium; RV, right ventricle.

(From Reddy VK, Faulkner M, Bandarupalli N, et al: Incremental value of live/real time three-dimensional transthoracic echocardiography in the assessment of right ventricular masses. Echocardiography 26:598–609, 2009.)

Figure 16-6 A giant myxoma of the left atrium causing obstruction of the mitral orifice.

(From Culp WC Jr, Ball TR, Armstrong CS, et al: Three-dimensional transesophageal echocardiographic imaging and volumetry of giant left atrial myxomas. J Cardiothorac Vasc Anesth 23:66–68, 2009.)

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).⁹

Figure 16-7 A and B, Example of echolucencies seen with cardiac masses suggesting intramass hemorrhage or necrosis of the tumor (arrowhead). Ao, aorta; LA, left atrium; LV, left ventricle; MV, mitral valve; RV, right ventricle.

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).⁷ A left atrial fibroma (Figure 16-9) was associated with Gardner syndrome.¹⁰

Figure 16-8 A right ventricular fibroma in a patient with history of previous incomplete resection of the same. The fibroma was much larger by three-dimensional compared with two-dimensional transthoracic echocardiography. RV, right ventricle.

Figure 16-9 A, A left atrial fibroma (arrow) is shown by three-dimensional transesophageal echocardiography. This mass was associated with Gardner syndrome with familial adenomatous polyposis and associated extracolonic growths, including fibromas. B, Left atrial fibroma. LAA, left atrial appendage; A1, A3, anterior scallops 1 and 3; P1, P3, posterior scallops 1 and 3.

(From Yang HS, Arabia FA, Chaliki HP, et al: Images in cardiovascular medicine. Left atrial fibroma in Gardner syndrome: Real-time 3-dimensional transesophageal echo imaging. Circulation 118:e692–e696, 2008.)

Papillary Fibroelastoma

Papillary fibroelastoma is the third most common tumor of the heart, with an incidence of 0.33% among autopsy series.¹¹ It is the most common tumor of the heart valves and is most frequently identified on the aortic valve (Figure 16-10), although all valves have been described (Figure 16-11; Video 16-7). The value of RT3DTTE was illustrated in a case presented by Singh and colleagues¹² with a papillary fibroelastoma of the pulmonary valve. RT3DTTE pinpointed the attachment point, which was helpful in planning valve-sparing surgery. Also, 3D cropping through multiple orthogonal planes revealed frondlike projections and no echolucencies, which helped differentiate the mass from a myxoma or thrombus (Figure 16-12). Le Tourneau and associates¹³ studied seven consecutive patients with this lesion who had surgical resection of the lesion and found feasibility of imaging the mass to be 100%. Correlation of the 3D volume size with the actual resected tumor was very good. They believed RT3DTTE helped with surgical planning in three of the seven patients; surgical planning is key when valve-sparing surgery is planned. Most of the lesions (five of seven) were on the aortic valve.¹³

Figure 16-10 A, An aortic fibroelastoma is seen protruding from the ventricular side of the aortic valve (arrow). B, Aortic fibroelastoma. LCC, left coronary cusp; NCC, noncoronary cusp; RCC, right coronary cusp.

(From Le Tourneau T, Polge AS, Gautier C, Deklunder G: Three-dimensional echography: cardiovascular applications. J Radiol 87:1993–2004, 2006.)

Figure 16-11 Papillary fibroelastoma (arrow) is shown on the tip of the anterior leaflet of the mitral valve. This patient had been asymptomatic; this was an incidental finding (see Video 16-7).

Figure 16-12 Papillary fibroelastoma of the pulmonary valve. A, The mass (arrowhead), imaged by two-dimensional echocardiography, is attached to the pulmonary valve. B, The same mass imaged by three-dimensional echocardiography (arrowhead). The arrow shows frondlike attachment to the valve. AO, aorta; PA, pulmonary artery; PV, pulmonary valve; RVO, right ventricular outflow tract.

(From Singh A, Miller AP, Nanda NC, et al: Papillary fibroelastoma of the pulmonary valve: Assessment by live/real time three-dimensional transthoracic echocardiography. Echocardiography 23:880–883, 2006.)

Sarcomas

Sarcomas are quite rare primary tumors of the heart but are, in fact, the most common type of primary malignant cardiac tumor, at least in the adult population. Angiosarcoma is the most common among cardiac sarcomas and typically arises in the right atrium, often adjacent to the inferior or superior vena cava. These tumors often are large and aggressive, sometimes occupying much of the right atrium (Figures 16-13 to 16-16; Videos 16-8 to 16-10). Suwanjutah et al¹⁴ described a case of leiomyosarcoma imaged by RT3DTTE (Figure 16-17). The notable incremental value of RT3DTTE was the composition of the mass. RT3DTTE, again, thanks to its cropping capability, allowed imaging of an area of echolucency, suggesting necrosis or hemorrhage surrounded by bandlike structures consistent with collagen. This image created a “donut” appearance. Excision and evaluation of the resultant histopathology revealed the same pattern of necrosis and vascular channels within the fibrotic tumor. The morphology seen in this case of the tumor by RT3DTTE was suggestive of tumor as opposed to a thrombus. Just as important, the size of the mass by RT3DTTE was significantly larger than when measured by 2DTTE.

Figure 16-13 Two-dimensional transesophageal echocardiography of a right atrial mass (arrow) found by biopsy to be angiosarcoma. Note the pericardial effusion.

Figure 16-14 Three-dimensional transesophageal echocardiography of a right atrial angiosarcoma (arrow).

Figure 16-15 A, Three-dimensional transesophageal echocardiography image of a right atrial angiosarcoma (arrows). B and C, Right atrial angiosarcoma with effusion (arrowhead) (see Videos 16-8 to 16-10).

Figure 16-16 Right ventricular sarcoma (arrow). LV, left ventricle; RA, right atrium; RV, right ventricle.

Figure 16-17 Leiomyosarcoma. Arrows depict area of tumor necrosis. AO, aorta; LV, left ventricle.

(From Suwanjutah T, Singh H, Plaisance BR, et al: Live/real time three-dimensional transthoracic echocardiographic findings in primary left atrial leiomyosarcoma. Echocardiography 25:337–339, 2008.)

Lymphomas

Lymphomas represent 5% of primary cardiac malignancies, although diagnosis is not commonly made during life due to nonspecific presenting symptoms. A case of non-Hodgkin lymphoma in the right atrium that presented as atrial fibrillation was described and imaged by RT3DTTE. Follow-up imaging was useful for chemotherapy cleanup and showed marked shrinkage of the mass.¹⁵

Carcinoid Syndrome

Cardiac involvement occurs in more than 50% of patients with carcinoid syndrome. The right-sided heart valves are characteristically involved, with the tricuspid valve particularly affected. As previously mentioned, the pulmonary valve is particularly challenging to image by echocardiography. In a series of cases reported by Nalawadi and colleagues ¹⁶ in three patients who were diagnosed with cardiac carcinoid, RT3DTEE performed well when determining involvement of the tricuspid and pulmonary valves (Figure 16-18). There was particular incremental value for viewing the tricuspid valve en face, particularly by RT3DTTE, which demonstrated a fixed, open-orifice tricuspid valve with severe tricuspid regurgitation. The pulmonary valve was seen well in only one of the four cases, and notable RT3DTEE findings were not visible in the images provided. However, the authors state that “RT3D was particularly helpful in showing carcinoid involvement of the pulmonic valve with thickening, retraction, and distortion, as well as, if present, identifying a mass on the valve.” Our own experience with RT3DTEE in carcinoid syndrome has been limited, but it is clear that the aortic arch view of the pulmonary valve would be useful in this setting (see Chapter 10).