Pulmonary atresia with ventricular septal defect. Further anatomical observations.

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Abstract
An anatomical study was undertaken of 25 human 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 6 aortic arch derivatives within the pericardial cavity. Specimens (18) 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 1 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. Anatomotic 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. A distinction can apparently 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 6th aortic arches failed to develop, lack of septation of the cardiac outflow tracts rendering them superfluous and only the early systemic-pulmonary connections persist. The condition is difficult or impossible to distinguish from pulmonary atresia with ventricular septal defect on clinical grounds. In the examples of pulmonary atresia 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.