Incidental Finding of Superior Vena Cava Mass Missed on Transesophageal Echocardiography but Seen on Epiaortic Imaging

A 48-yr-old woman presented with cough, fever, and lethargy. Transesophageal echocardiography (TEE) identified tricuspid valve vegetations and the patient was scheduled for surgery. After induction of general anesthesia, a 1-wk-old right subclavian triple-lumen venous catheter was removed and a right femoral venous line was placed. TEE confirmed tricuspid valve vegetations, but was otherwise unremarkable. TEE examination of the superior vena cava (SVC) in the midesophageal (ME) bicaval and ascending aortic short axis (SAX) views revealed no abnormal findings (Video Clips 1 and 2; please see video clips available at www.anesthesia-analgesia.org). However, during routine epiaortic scanning of the ascending aorta, a SVC mass was noted (Fig. 1; Video Clip 3). After re-evaluation of the bicaval view by withdrawing the TEE probe more cephalad than was done for the originally derived standard view, a mobile mass was also noted in the SVC (Fig. 2B; Video Clip 4). The initial plan for bicaval cannulation was aborted. The inferior vena cava was instead cannulated, cardiopulmonary bypass was initiated and the SVC thrombus was removed. The infected tricuspid valve was replaced with a pericardial valve and the patient separated from cardiopulmonary bypass uneventfully. Pathology subsequently identified the SVC mass as laminated thrombus, whereas the tricuspid masses included laminated thrombi with copious coccal bacterial involvement.Figure 1.: Epiaortic image of a mass in the SVC is noted. This is a modified epiaortic view of the ascending aorta in the long axis and the SVC in short axis. SVC = superior vena cava.Figure 2.: ME bicaval TEE views are compared here. (A): Standard ME bicaval view showing no obvious evidence of SVC mass. (B): Modified ME bicaval view showing a serpentine and irregular mass in the SVC. ME = midesophageal; TEE = transesophageal echocardiography; SVC = superior vena cava; RA = right atrium; LA = left atrium; RPA = right pulmonary artery.The differential diagnosis for a SVC mass includes foreign body (central line or pulmonary artery catheter), vegetation, thrombus, tumor or artifact. On TEE, vegetation may appear as a mobile, echogenic mass with a gray scale similar to the myocardium. Although right atrial vegetations typically occur on the atrial surface of the tricuspid valve, there are rare reports of vegetations within the SVC, inferior vena cava, Eustachian valve, and other right atrial locations.1 Echogenic appearance of thrombus varies according to underlying pathology. Thrombi associated with low intracardiac blood flow tend to appear laminated, nonhomogeneous, and are often immobile and layered along the atrial free wall. Thrombi attached to foreign body often appear serpentine and irregular and are generally mobile. They are often seen attached to the foreign body and extend into the right atrium. Thrombi embolizing from peripheral veins may also appear serpentine, irregular, and mobile and sometimes appear to float freely in the right atrium without obvious endocardial attachment. Although prior surgery within 30 days or a history of deep vein thrombosis (DVT) are the primary risk factors for lower-extremity DVT, a recent history of an upper body central venous catheter is the main risk factor for occurrence of an upper-extremity DVT.2 Additionally, a central venous catheter in the setting of cancer increases the likelihood for developing upper-extremity DVT. Although the “gold standard” for diagnosing a DVT is contrast venography, the initial diagnostic method of choice is Duplex ultrasonography. Duplex ultrasonography allows for simultaneous ultrasonic imaging of the vessel and blood flow measurement by Doppler analysis. Incompressibility of a venous segment with the ultrasound probe, direct visualization of intraluminal thrombus, incomplete filling of the vein with color flow Doppler and abnormal flow measurements during respiration, and absence of cardiac pulsatility support the diagnosis of DVT.3 These ultrasonographic diagnostic methods can be used for diagnosing upper-extremity and internal jugular venous thrombi, but with more central veins as the innominate and SVC, ultrasonographic diagnosis is limited by inaccessibility of optimal echocardiographic windows caused by overlying anatomic bony structures as the clavicle and sternum. The SVC is a vessel that is approximately 7 cm in length and begins at the confluence of the right and left innominate veins and ends by entering the right atrium.4 When compared to transthoracic echocardiography, TEE affords better imaging windows of the SVC. With the standard ME bicaval view, the SVC can be seen up to 3–5 cm cephalad from the SVC-right atrial junction (Fig. 2A). However, as demonstrated in this case, by withdrawing the TEE probe even more cephalad than required to derive the standard ME bicaval view, the SVC can be better visualized and to a greater extent (Fig. 2B). Another standard TEE view that visualizes the SVC is the ME ascending aortic SAX view. This view shows the SVC at the level of the mid-ascending aorta. However, in many patients, it is not always possible to obtain adequate acoustic windows to view the SVC in the ME ascending aortic SAX view secondary to the location of the bronchial tree in relation to the esophagus and the great vessels. Hence, epiaortic scanning of the great vessels may provide additional diagnostic information. In particular, epiaortic scanning may provide diagnostic information that is additional to that derived from standard TEE views, particularly with regards to the more cephalad regions of the SVC (Fig. 1).5 One potential criticism regarding the standard ME bicaval TEE images obtained in this case could be that the gain setting may have been excessive. Excessive gain can distort image resolution and lead to diagnostic errors. Optimal gain in this setting would have made blood appear black and echo free. However, by comparing the standard and then later modified ME bicaval views that we derived to view the SVC (Figs. 2A and B), it appears that the thrombus would not have been detected in the standard ME bicaval view even with optimized gain settings (Fig. 2A). Recently, the American Society of Echocardiography and the Society of Cardiovascular Anesthesiologists recommended a comprehensive epiaortic ultrasonographic examination that includes a minimum of five views of the ascending aorta and arch.5 This case illustrates the value of incorporating a comprehensive epiaortic ultrasongraphic examination, especially in the setting of right-sided endocarditis, where careful assessment of the SVC by TEE and epiaortic scanning is possible and advisable in order to assess undiagnosed thrombi or vegetations. This case also demonstrates the importance of an individualized comprehensive examination and emphasizes that certain expertise may be required to image structures not commonly visualized by conventional TEE and epiaortic windows.