Deviation of the atrial septum primum predisposing to local thrombus formation

In a substantial proportion of patients with recent systemic embolization, no evident source of embolism or predisposing factors can be verified. As yet unidentified cardiac abnormalities may play a role in the pathogenesis of the peripheral embolic events. The authors report the case of a 72-year-old man who presented with atrial fibrillation and recurrent in situ thrombus formation in the territory of the fossa ovalis. A deviated and malattached atrial septum primum without a patent foramen ovale may predispose to local thrombus formation in patients with atrial fibrillation. Further studies are required to establish the clinical importance of such an atrial septal malformation in specific subgroups of patients with ischemic stroke.