Right-to-Left Shunt Evaluated at the Aortic Arch by Contrast-Enhanced Transesophageal Echocardiography

OBJECTIVE: The right-to-left shunt (RLS) is diagnosed by contrast-enhanced transesophageal echocardiographic monitoring of the bilateral atria (cTEE-BA). However, the procedure is often disturbed by nonsmoke spontaneous individual contrast (NSSIC) with fast motion, which appears in the left atrium after respiratory maneuvers without administration of a contrast medium and moves past in several seconds. We attempted to perform cTEE monitoring of the aortic arch (cTEE-AA) for evaluation of the RLS and compared the findings with those of cTEE-BA. METHODS: Both cTEE-BA and cTEE-AA were performed in 168 patients with ischemic stroke (133 men and 35 women; mean age +/- SD, 62.0 +/- 14.4 years). The frequency of NSSIC in the left atrium was compared with that in the aortic arch during the respiratory maneuver. When contrast much brighter than the NSSIC was visualized in the left atrium and the aortic arch during the respiratory maneuver with administration of the contrast medium, we considered the RLS to be positive in the cTEE-BA and cTEE-AA, respectively. Findings were then compared between the 2 examinations. RESULTS: Nonsmoke spontaneous individual contrast was more frequently observed in the left atrium than the aortic arch (61.3% versus 14.9%; chi2 test, P < .0001). The RLS was positive in 34 patients in the cTEE-BA and in 39 patients in the cTEE-AA. The sensitivity and specificity of the cTEE-AA for the cTEE-BA were 100% and 96.3%, respectively. CONCLUSIONS: The cTEE-AA may be an alternative method for detection of an RLS, especially in patients with a large amount of NSSIC in the left atrium.