ABSTRACT
Atrial septal pouch is a common anatomic variant of the interatrial
septum and a nidus for thrombus formation. Left-sided atrial septal
pouch has been associated with an increased risk of cryptogenic stroke.
We described a case of left-sided atrial septal pouch thrombus,
incidentally found prior to transseptal puncture during Watchman device
placement. This case highlights the importance of a thorough
echocardiographic evaluation of the atrial septum prior to transseptal
access and recognition of this finding as a potential cardiac source of
embolism.