Right-to-Left-Shunts Detected by Transesophageal Echocardiography and Transcranial Doppler Sonography

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Abstract
Background: Transesophageal echocardiography (TEE) and transcranial Doppler sonography (TCD) can identify right-to-left-shunts that predispose to paradoxical embolism. In a large cohort we compared the results of both techniques. Methods: 222 patients were investigated by both techniques using the contrast agent Echovist®-300 and performing each test once without and once with the Valsalva maneuver (VM). Results: TEE-proven right-to-left-shunts were detected by TCD with a high sensitivity of 94%. In addition, TCD revealed shunts not noted during TEE in about 20% of all patients studied. These shunts are in general smaller than those concordantly identified; however, 9% of the patients without a TEE-proven shunt presented with a shunt that allows a considerable amount of contrast medium to pass. There were 12% more microbubbles detected in the right middle cerebral artery than in the left middle cerebral artery during the TCD test performed with VM, but not during the TCD test performed without VM. Conclusions: Contrast-enhanced TEE and TCD are complementary methods in the assessment of stroke and stroke-prone patients. The side difference of microbubbles may indicate a selective streaming of cardiac emboli during VM.