MR findings of a rare defect, coronary sinus ASD.

The coronary sinus drains the cardiac veins into the right atrium. An unroofed coronary sinus is the least common type of atrial septal defect (<1%). An unroofed coronary sinus also communicates with the left atrium, in addition to its normal communication with the right atrium. This defect is difficult to diagnose. MR provides accurate anatomic details about the location and size of defect. Phase contrast velocity-encoded MR also helps towards quantifying the shunt volume. This case represents classical findings of this rare defect. Our patient first presented in the 8th decade with features of right heart failure.