Abstract
A 21-year-old man with coronary sinus atrial septal defect (ASD) was treated successfully. This case had been diagnosed as an ASD without a lower margin preoperatively but we confirmed this to be a coronary sinus ASD intraoperatively, and this case was classified as partially unroofed coronary sinus without PLSVC. The diagnosis of coronary sinus ASD before operation is sometimes difficult. Therefore we should pay attention to the location of the defect and the dilated coronary sinus in echocardiography, and the course of the cardiac catheter entering into the left atrium, for a correct diagnosis. In this case, the defect was located in the vicinity of the ostium of a large coronary sinus, therefore we could close the defect between the CS and the LA using a heart-shaped patch without any damage to the AV node.
