Mitral valve cleft without cardiac septal defect causing severe mitral regurgitation but allowing long survival

Partial atrioventricular “defect” includes a spectrum of 5 anatomic anomalies. Some patients have all 5 and others have only 1 or 2. The 5 are the following: (1) defect in the lower portion of the atrial septum, so-called primum atrial septal defect; (2) defect in, or absence of, the posterobasal portion of ventricular septum; (3) cleft, anterior mitral leaflet; (4) anomalous chordae tendineae from the anterior mitral leaflet to the crest of the ventricular septum; and (5) partial or complete absence of the septal tricuspid valve leaflet. There are at least 4 potential functional consequences of these 5 anatomic anomalies: (1) shunt at the atrial level, (2) shunt at the ventricular level, (3) mitral regurgitation (MR), and (4) obstruction to left ventricular outflow. Well over 95% of patients with partial atrioventricular defect have a primum type atrial septal defect, and most of those without a primum defect have a shunt at the ventricular level. The occurrence of MR from a cleft in the anterior mitral leaflet unassociated with a defect in either atrial or ventricular septa is extremely rare. Such was the case, however, in the patient to be described herein.