A 29 year old woman with NYHA functional class II and large secundum type atrial septal defect (ASD) underwent successfully percutaneous ASD closure with Figula ASD occluder (no. 30) without any peri-procedural complication. After 2 days she underwent transthoracic echocardiography and a large hypo-echoic mass was seen on left atrial side of implanted device in multiple views, suggestive of thrombosis or echocardiographic beam width artifact? A diagnostic enigma!