Recurrent cerebral embolism and impending detachment of a previous nonmobile left atrial thrombus following initiation of anticoagulant therapy in a patient with nonvalvular atrial fibrillation.

A 65-year-old female with nonvalvular atrial fibrillation who presented with a transient ischemic attack was admitted to our hospital. Transesophageal echocardiography (TEE) revealed a nonmobile thrombus attached to the wall of the left atrial appendage. She suffered from a new episode of syncope on the 8th day following initiation of anticoagulant therapy. Follow-up TEE indicated not only that the left atrial (LA) thrombus decreased in size but also that the previous nonmobile thrombus became mobile and showed impending detachment. Urgent surgery was subsequently performed to remove the LA thrombus, and the patient recovered uneventfully. In conclusion, anticoagulant therapy may precipitate partial fragmentation or partial detachment of LA thrombus.