Libiran, Nicole BiancaMohiuddin, AmerKataoka, Makoto2025-09-152025-09-152025-10-12Libiran NBS, Mohiuddin A, Kataoka M. Pitfalls in Diagnosing Left Atrial Appendage Thrombus: Lessons from a False-Positive TEE in Mitral Valve Surgery. Poster to be presented at: American Society of Anesthesiologists; October 10-14, 2025; San Antonio, Texas.https://hdl.handle.net/1805/51018A 47-year-old female with severe mitral stenosis underwent open mitral valve replacement. Preoperative and intraoperative TEE suggested a left atrial appendage thrombus, but no thrombus was found when the atrium was opened. While TEE is the gold standard for LAAT diagnosis, its accuracy can be affected by trabeculations, reverberation artifacts, and spontaneous echogenic contrast. Adjunct imaging techniques, including color flow Doppler, 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, complicating diagnosis.transesophageal echocardiographyspontaneous echocardiographic contrastleft atrial appendagethrombusfalse-positivecardiac CTPoster