Large Left Atrial Appendage Causing Cryptogenic Stroke.

Cryptogenic stroke is a subtype of ischemic stroke for which no identifiable cause is found after routine diagnostic evaluation. It accounts for roughly 25% of ischemic strokes. Structural cardiac abnormalities such as patent foramen ovale, atrial septal defect (ASD), and a large left atrial appendage (LAA) are commonly associated risk factors in patients with cryptogenic stroke. We report a case of a patient with a history of a surgically repaired ASD found to have a large LAA without identifiable thrombus on both transthoracic echocardiogram and transesophageal echocardiogram after presenting with an acute cryptogenic stroke in the absence of any arrhythmias. We aim to emphasize the importance of the LAA, particularly if large, in the pathogenesis and development of cryptogenic strokes. Additionally, we discuss the necessity for clearly defined guidelines on whether to start anticoagulation in these patients.