[Surgical landmarks of course of atrioventricular conduction system]

There is a certain tendency in the relationship between the distribution of the conduction system and the type of VSD as classified by Soto and coworkers. The course of the conduction system and its surgical landmarks were investigated histologically in various cardiac anomalies. In perimembranous inlet VSD, the His bundle ran superficially on the crest of the ventricular septum. It ran on the left ventricular aspect and somewhat deeply in trabecular VSD and far deeply in infundibular VSD. In perimembranous inlet or trabecular VSD, the RBB laid beneath or just anterior to a series of upper-uppermost accessory papillary muscle when these were present and descended posteroinferior to the MPM, basically as in the normal heart. The upper-uppermost AcPM are reliable landmarks for the RBB. The RBB descended just anterior to the so called MPM (embryologically the uppermost AcPM--Van Mierop) in infundibular VSD and TOF. These findings have provided us useful bases for suture placement to avoid conduction disturbance.