With the increased use of transesophageal echocardiography (TEE), systemic emboli from atheromas in the thoracic aorta are being identified more often. Recent studies have suggested that protruding aortic plaques may be an important source of iatrogenic stroke and embolic events in elderly patients. TEE is a semi-invasive method that usually requires anesthesia and is unsuitable for screening potentially high-risk patients. It also does not reliably visualize the upper part of the ascending aorta and the proximal aortic arch. Tenenbaum and associates compared the effectiveness of TEE with that of unenhanced dual-helical computed tomography (CT) in diagnosing protruding aortic atheromas.
Thirty-two consecutive patients at least 50 years of age who had recent ischemic strokes, systemic emboli, or both were included in the study. All patients underwent assessment with both TEE and dual-helical CT.
TEE revealed a protruding aortic atheroma in 15 of the patients (47 percent). Dual-helical CT revealed protruding atheromas in 13 of the 15 patients with positive TEE scans (87 percent). The two remaining patients had negative CT scans.
In patients without evidence of atheromas on TEE, CT revealed the absence of atheromas (in areas defined as visible at TEE) in 14 patients and the presence of atheromas in three. Dual-helical CT had a sensitivity of 87 percent and a specificity of 82 percent, with an overall accuracy of 84 percent.
Of the 36 protruding aortic atheromas depicted with TEE, 34 were correctly identified with CT. Two noncalcified plaques remained undetected. Three nonprotruding aortic plaques depicted on TEE were diagnosed as protruding atheromas on CT. Of the 34 atheromas correctly identified with CT, 13 were located in the arch and 21 in the descending aorta.
The main finding of this study is the potential of CT to enable detection of a protruding aortic atheroma, particularly in the ascending aorta and the arch. Using dual-helical CT instead of the widely used single-section CT provides acquisition of data twice as quickly. The rapid CT technique enables examination of the ascending aorta and the arch during the holding of a single breath, preventing respiratory motion artifacts. This is critical for measuring and defining protruding atheromas.
The advantages of CT over TEE include its noninvasive character, its suitability for screening large populations and the possibility of complete visualization of the ascending aorta and the proximal arch. This permits evaluation of the location and extent of the plaque. Obvious disadvantages include the inability of CT to detect intracardiac sources of emboli. The authors suggest that positive unenhanced dual-helical CT should be followed by contrast material injection or TEE.
The authors conclude that despite some limitations, unenhanced dual-helical CT may become complementary and occasionally superior to TEE in the rapid, noninvasive detection of protruding aortic atheromas in areas not well visualized with TEE.