231 consecutive patients undergoing elective cardiac surgery (between 1989 and 1995) which required opening of the left atrium (224 for mitral valve repair/replacement, 7 for left atrial myxoma). 36% were in atrial fibrillation at the time of the study, an additional 20% had a history of atrial fibrillation. TEE was done using single plane probe (48 patients), biplane probe (69 patients) and multiplane probe (114 patients). TEE was interpreted independently by the observer performing the study and by another observer reviewing the videotape. The left atrium and left atrial appendage were directly visualized and explored by the surgeon.
In the 231 patients, TEE identified 14 left atrial thrombi, ranging in size from 3 to 80 mm (half of these between 3 and 10 mm). 11 of the 14 were confined to the left atrial appendage. 12 of the 14 were identified by both observers, 2 by only one observer. At surgery, all 12 thrombi identified by both observers were confirmed. The two thrombi seen by only one observer was not confirmed at surgery. No thrombi were found at surgery that were not seen on TEE.
Of 11 thrombi seen with biplane or multiplane probes, 10 were visualized in the horizontal (0 degree) plane, but one was not (and thus would probably not have been detected with a monoplane transducer).
In this study, TEE had a sensitivity of 100% and a specificity of 99% for detection of left atrial thrombi.
In an excellent accompanying editorial, B. Gersh and J. Gottdiener make several important points. First of all, since the atria often remain mechanically stunned for several days after successful restoration of sinus rhythm, the absence of a thrombus at the time of cardioversion does not obviate the need for anticoagulation for several weeks post-cardioversion. Second, the very high quality of the echocardiograms obtained here, related to the expertise of the investigators, the quality of the equipment and especially the very relaxed state of the patients (under general anesthesia) will not necessarily be duplicated in clinical practice. In final analysis, the validity of the TEE approach to cardioversion in atrial fibrillation requires clinical confirmation which has been partially accomplished but is still largely ongoing.
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