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.