Thrombus formation during percutaneous closure of an atrial septal defect with an Amplatzer septal occluder

Percutaneous closure of an ostium secundum-type atrial septal defect is typically a safe and effective therapeutic option in the presence of significant shunting or paradoxical embolism. Infrequently, however, periprocedural sequelae occur.Herein, we report the cases of 2 patients, each of whom underwent transcatheter closure of an atrial septal defect with the use of an Amplatzer Septal Occluder under transesophageal echocardiographic guidance. In both patients, acute thrombi formed periprocedurally, despite preprocedural anticoagulation. In patient 1, the infusion of unfractionated heparin for 24 hours prevented the recurrence of thrombus; in patient 2, the thrombus was isolated under the arm of the occluder, and unfractionated heparin was infused. Both patients were asymptomatic and without detectable thrombus after the procedure and at follow-up. These reports highlight a rare early sequela and the importance of transesophageal echocardiographic monitoring during the percutaneous closure of an atrial septal defect.