Intraprocedural left atrial appendage thrombus formation during percutaneous left atrial appendage closure: A case report.

UNLABELLED: Percutaneous left atrial appendage closure (LAAC) is an established strategy for stroke prevention in patients with atrial fibrillation (AF). Although device-related thrombus after LAAC has been reported, intraprocedural thrombus formation within the left atrial appendage (LAA) during the procedure is rare. A 78-year-old male with persistent AF underwent LAAC under ongoing warfarin and clopidogrel therapy. Intraprocedural transesophageal echocardiography (TEE) demonstrated markedly reduced LAA flow with spontaneous echo contrast and sludge, which transiently resolved after isoproterenol administration. Device deployment required multiple recaptures and repeated repositioning due to difficulty in achieving stable anchoring. During these manipulations, a 14-mm mobile thrombus developed within the LAA, despite the activated clotting time being maintained above 300 s, which prompted immediate termination of the procedure. The patient experienced no post-procedural neurological deficits, and follow-up TEE on day 4 confirmed complete thrombus resolution. Contributing factors to intraprocedural LAA thrombus formation were considered to include severely reduced LAA flow, repeated device manipulation, and transient procedural bradycardia. Early recognition through continuous TEE monitoring was critical for preventing embolic complications. LEARNING OBJECTIVE: Intraprocedural thrombus formation within the left atrial appendage (LAA) during LAA closure can occur even under adequate anticoagulation.Potential contributing factors include reduced LAA flow, repeated device manipulation, and transient bradycardia, which may synergistically promote acute thrombus formation.Continuous intraprocedural transesophageal echocardiographic surveillance is essential for early detection and timely termination of the procedure to prevent embolic complications.