Pulmonary atresia with ventricular septal defect further anatomical observations

Abstract

An anatomnical study was undertaken of 25 hearts with pulmonary atresia and ventricular septal defect, giving special attention to the morphology of the pulmonary outflow tract and the nature of the arterial supply to the lungs. A common feature of all hearts studied was the presence of sixth aortic arch derivatives within the pericardial cavity. Eighteen specimens presented with pulmonary atresia with ventricular septal defect in situs solitus, with atrioventricular concordance and normally related great arteries, that is with the pulmonary artery remnant anterior and to the left of the aorta. A blind or atretic pulmonary infundibulum was observed in all but one of these cases. In the remaining 7 specimens, the atretic pulmonary trunk was posterior to the aorta. The pulmonary arterial blood supply was either through a ductus arteriosus or systemic-pulmonary anastomotic vessels. Anastomotic vessels were never observed together with a ductus, suggesting that the systemic-pulmonary vessels represent persistence of early arterial connections with the lungs when the ductus fails to develop. The result of this study when compared with our previous studies indicates that a distinction can be made between pulmonary atresia with ventricular septal defect and persistent truncus arteriosus with absent pulmonary arteries ('type IV'). The latter is considered to be a true truncus arteriosus in which the arterial connections with the pulmonary vascular bed through the sixth aortic archesfailed to develop, lack of septation of the cardiac outflow tracts rendering them superfluous, and thus only the early systemic-pulmonary connections persist. However, the condition is difficult or impossible to distinguish from pulmonary atresia with ventricular septal defect on clinical grounds. In the examples of pulmonary airesia with ventricular septal defect and posteriorly placed pulmonary trunk remnants, the pulmonary circulation was always supplied by the ductus arteriosus; systemic-pulmonary arteries were never seen. The mechanism producing atresia of the posteriorly positioned pulmonary infundibulum seems to be different from the form with anteriorly placed pulmonary infundibulum, as no deviation of the conal septum was seen and the ventricular septal defect was rarely a malalignment defect.