The formation of an intracardiac thrombus is one of the most serious complications of atrial fibrillation and a common cause of stroke and embolism in other systemic arteries. In the present case, we document the fragmentation of a large thrombus in the left atrial appendage, resulting in embolization of the left common femoral artery.

A 72-year-old woman with a history of permanent atrial fibrillation and receiving permanent anticoagulation was admitted to the cardiology department because of a large mass (22×16mm) attached to the left atrial appendage, noted as a chance finding in a chest computed tomography study. The finding was consistent with a thrombus and this was confirmed by echocardiography.

On admission, anticoagulation with sodium heparin was administered. After 10 days, a control transesophageal echocardiogram was performed, and a large mobile thrombus could be seen, of a size slightly smaller than that observed in the previous echocardiogram (video 1). During the echocardiographic study, the thrombus detached and partially fragmented, with most of the material passing through the aortic valve (video 2). A small residual thrombus and spontaneous contrast remained in the left atrial appendage (video 3).

After 48hours, the patient’ clinical condition was consistent with acute arterial embolism in the left leg. An embolectomy was performed, and a large saddle thrombus was removed from the bifurcation of the common femoral artery. The thrombus extended to the deep and superficial femoral arteries.

The delay between the thrombus entering the arterial circulation and the clinical symptoms in this case was likely due to its straddling the bifurcation and later spreading into the branches.