A Case Report on the Pitfalls in Diagnosing Left Atrial Appendage Thrombus: Lessons From a False-Positive Transesophageal Echocardiography (TEE) in Mitral Valve Surgery.

A 47-year-old female with severe mitral stenosis underwent open mitral valve replacement. Preoperative and intraoperative transesophageal echocardiography (TEE) suggested a left atrial appendage thrombus, but no thrombus was found when the atrium was opened. While TEE is the gold standard for left atrial appendage thrombus diagnosis, its accuracy can be affected by artifacts, as well as normal anatomical structures, such as the coumadin ridge or pectinate muscle trabeculations, which may mimic thrombus, and by spontaneous echogenic contrast. Adjunct imaging techniques, including 3D TEE, left atrial appendage outflow velocity, and contrast-enhanced imaging, can improve accuracy. Cardiac CT is also a valuable alternative. In this case, the mass may have resulted from blood stasis rather than a true thrombus, highlighting the diagnostic challenges in such scenarios.