Acute Left Atrial Thrombus Formation on Resected Resid- ual Cribriform Septum after Atrial Septal Defect Surgery

<p><em>Acute left atrial thrombosis at the site of the resection of the primary cribriform septum is an exceedingly rare and important complication after atrial septal defect (ASD) closure with a pericardial or synthetic patch. This case report presents a mobile thrombus noted on the left atrium at the raw surface site of a resected cribriform primary septum that was not caught in the suture line with the pericardial patch for the closure of the ASD in a 30-year-old woman with an uncomplicated ASD surgery. The patient had no symptoms in the postoperative period, and routine postoperative transesophageal echocardiography revealed a large pedunculated and mobile mass (thrombosis) at the left atrial side of the interatrial septum at the level of the implanted pericardial patch. The thrombus was successfully treated with surgery. The patient had an uneventful recovery in the postoperative period and was discharged from the hospital 15 days after admission. One-year follow-up showed no evidence of clot recurrence in the left or right atrium.</em>