Mitral Atresia Associated with Pulmonary Venous Anomalies.

In mitral atresia with a closed or narrowly patent foramen ovale, anomalous pulmonary venous connexions may occur that function as collateral pathways for the return of pulmonary venous blood to the heart. In 2 cases (Edwards and DuShane, 1950; Lucas et al., 1962), although all the pulmonary veins' connected normally, an anomalous channel-termed a levo-atriocardinal veinformed the collateral pathway connecting the left atrium to the left innominate vein. This report describes coexisting pulmonary venous anomalies in 5 cases among a group of 29 cases of mitral atresia studied by us. In 4 of these 5, the anomalous pulmonary veins took the form of anomalous pulmonary venous connexion: in the remaining 1 the pulmonary venous anomaly was represented by cor triatriatum. In 3 of the 5 cases (Group I) mitral atresia and premature closure of the foramen ovale coexisted. The anomalous pulmonary venous connexions in this group provided collateral routes for the flow of pulmonary venous blood, and can be understood as developing in response to obstruction at the foramen ovale when the mitral valve is atretic. In the remaining 2 cases (Group II) no such causative factor could be invoked for the presence of the pulmonary venous anomalies, since in each an interatrial communication was present. In one of the latter group total anomalous pulmonary venous connexion coexisted with a common atrium. In the other, cor triatriatum coexisted with a patent foramen ovale-the four individual pulmonary veins connecting to the upper (accessory) left atrial chamber. In all 5 cases, regardless of the specific anatomical arrangement, obstruction to pulmonary venous flow occurred. Grossly, in the 4 cases where the lungs were available for study, this organ appeared much congested and cedematous and the pleural surfaces showed a reticulated pattern of distended lymphatic channels. Histologically, there was medial hypertrophy of muscular arteries with very prominent elastic membranes, medial hypertrophy of the arterioles, congestion of alveolar walls, and dilatation of lymphatics (Fig. 1). The purpose of this report is to define the pulmonary venous anomalies in 4 of the 5t cases. Two of them (Cases 1 and 3) indicate the complexity of the pulmonary venous system that may develop when obstruction to flow is present during the stages when the lungs and their respective vascular beds are developing. The material also will indicate how normal mediastinal structures may contribute to obstruction of anomalous pulmonary veins.