Left-sided migration of Sideris button atrial septal occluder device.

We report the case of a left-sided migrated 'Sideris button' atrial septal defect occlusion device 6 years post-implantation with a residual secundum atrial septal defect and left atrial mass. The aims of this case report are to highlight an uncommonly seen atrial septal occlusion device, the importance of a complete echocardiographic examination of the path traversed by the device to assess for local trauma to structures, and the additional anatomical information gained and diagnostic use of intraoperative 3D transoesophageal echocardiography.