Comparison of diagnostic techniques for the detection of a patent foramen ovale in stroke patients.

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Abstract
The prevalence of a patent foramen ovale has been shown to be increased in patients with ischemic stroke. Transesophageal echocardiography, transthoracic echocardiography, and transcranial Doppler examination with contrast injection can all be used to search for a patent foramen ovale. We compared the accuracy of these techniques for identifying a patent foramen ovale in 49 patients with acute ischemic stroke or transient ischemic attack. Transcranial Doppler examination of the right middle cerebral artery was performed during simultaneous transthoracic echocardiography with aerated saline injection, and again during transesophageal echocardiography; the latter was adopted as the "gold standard" for assessing the sensitivity of the other two tests. Contrast transesophageal echocardiography detected a patent foramen ovale in 19 of 49 patients (39%), during normal respiration in 15 of them and during Valsalva maneuver in 4. Transcranial Doppler correctly identified 13 patients with a patent foramen ovale and all 30 patients without it. Therefore, the sensitivity of transcranial Doppler was 68% (13/19), and its specificity 100% (30/30). The 6 patients misclassified by transcranial Doppler (false negatives) had a very small right-to-left shunt detected by transesophageal echocardiography. Contrast transthoracic echocardiography was found to be the least sensitive test, detecting a patent foramen ovale in only 9 of 19 patients (47%). The specificity of transthoracic echocardiography was 100% (30/30 patients). The low sensitivity of transthoracic echocardiography was principally due to the suboptimal image quality obtained in false-negative patients. Both transcranial Doppler and transthoracic echocardiography were more sensitive in patients with cryptogenic stroke than in patients with stroke of determined origin. This may indicate the presence of larger, more easily detectable shunts in patients with cryptogenic stroke. Transesophageal echocardiography is more sensitive than transcranial Doppler examination in detecting a patent foramen ovale, but only in cases of minimal right-to-left shunts, the clinical relevance of which remains to be established. The sensitivity of transthoracic echocardiography is heavily hampered by the frequency of inadequate heart visualization.