The ductus arterious and associated cardiac anomalies in interruption of the aortic arch.

Seventeen heart specimens with aortic arch interruption, a ductus-dependent anomaly, were investigated. In all specimens the cardiac anatomy favoured a preferential flow into the pulmonary artery (from which the blood could reach the descending aorta through the ductus). Ten specimens had the interruption proximal to the left subclavian artery (type B) and nine of these presented solely with an outflow tract septal defect. On the other hand, six of seven specimens with the interruption distal to the left subclavian artery (type A) were associated with more complex heart malformations. The ductus was studied histologically in the 12 available arches without surgical intervention. The structure of the ductal wall, the components of which could extend considerably into the descending aorta and the pulmonary artery, ranged from that seen in a normal, mature ductus with prominent intimal cushions, to a totally abnormal persistent type with no intimal cushions and with marked elastification. This variability in ductal wall structure and the distribution of ductal tissue in the descending aorta and pulmonary artery has clinical and surgical consequences.

The concurrence of dimensional aortic arch anomalies and abnormal left ventricular muscle bundles.

This anatomical study was designed to evaluate the concept that reduced blood flow through the embryonic preductal aorta contributes to the pathogenesis of dimensional aortic arch anomalies. For that purpose the intracardiac anatomy of 151 specimens was examined, of which 22 had an interruption, five atresia, 76 tubular hypoplasia, and 48 local coarctation of the aortic arch. Associated malformations were found in 148 specimens (98%); the remaining three (2%) had isolated local coarctation. Anomalies predisposing to reduced aortic blood flow were present in 128 specimens (85%). Among the potential obstructive factors affecting early morphogenesis, three left ventricular muscular structures seem to be particularly important: (1) the anterolateral muscle bundle, (2) the posteromedial muscle, and (3) leftward deviation of the anterior part of the ventricular septum. Obstructing combinations with these types of anomaly were identified in 77 cases (51%). The embryologic aspects of these muscular structures are discussed.