Residual right-to-left shunt following repair of atrial septal defect.

Information about 5 patients with residual right-to-left shunts following repair of an atrial septal defect is presented. In each patient the defect was located low in the atrial septum adjacent to the inferior vena cava. During operation, either the eustachian valve of the inferior vena cava had been mistaken for the lower margin of the defect or the lower portion of the defect was not closed; blood flow was then diverted from the inferior vena cava into the left atrium. To prevent this occurrence, the inferior margin of the atrial septal defect should be closed first.