We describe the case of a 66 years-old patient, submitted to percutaneous closure of an ostium secundum atrial septal defect ( ASD ), with an " Amplatzer ASO 20 mm " ( Medical AGA Corp., MN (. There were no immediate complications and no residual leak. Eleven days after the procedure, atrial fibrillation ( AF ) ensued, followed by an acute myocardial infarction ( distal occlusion of the circumflex artery ). Three days later, this patient had also a transitory ischemic accident. Percutaneous closure of ASD is a procedure that can be associated with a few complications, namely AF and thromboembolic events. Although common, the use of dual antiplatelet therapy doesn't have an established efficacy to prevent these cases.