ATRESIA of the mitral valve, often with associated aortic valve atresia or hypoplasia of the aorta, is an uncommon congenital cardiac defect that leads to death in early infancy. In her classic monograph, Maude Abbott1 reported that five specimens were encountered in 1,000 postmortem examinations of patients with congenital heart disease. The lesion has been estimated to occur once in 50,000 children.2
The etiology of this malformation is not known. Among the theories advanced are: that the usual bending of the primary cardiac tube is distorted, (Spitzer3-5); that growth of the interventricular septum is maldirected (Moenckeberg6); that the septum primum and the endocardial cushion are fused (Brockman7); that the truncus arteriosus is unevenly partitioned (Castrovinci and Cucci8); and that it is the result of fetal endocarditis (Farber and Hubbard9).
Diagnosis is difficult since the anomaly must be differentiated from all conditions that