An interatrial tunnel: a rare form of atrial septal defects.

Atrial septal defects (ASDs) account for approximately 6%-10% of congenital heart defects. The well-known types of atrial septal communications are the ostium secundum, ostium primum, sinus venosus types, and coronary sinus defects. A 50-year-old female was referred for TEE for better assessment of MR severity and mechanism. 2D/3D-TEE showed a rare combination of different abnormalities; bi-leaflet mitral valve prolapse, cleft P2, cor triatriatum sinister, and a tunnel-shaped IAS communication. To the best of our knowledge, this is a very rare case with a rare form of atrial septal defect that was not described before. We named this defect an interatrial tunnel.