Left Atrial Septal Pouch Thrombus: An Unusual Cause of An Embolic Stroke

A large proportion of ischemic strokes have an undetermined cause and are considered “cryptogenic.” A left atrial septal pouch (LASP) develops due to incomplete fusion of the septa primum and secundum, forming a pocket at the interatrial septum. It can be a potential site of blood stasis with resultant thrombus formation. LASP has a higher prevalence among patients who present with cryptogenic stroke, but it is rare to visualize a thrombus in the LASP. We present a case of stroke with visualization of a LASP with in-situ thrombus confirming a pathogenic role.