As open heart surgery progresses, attention is focused not only on new procedures but also on reducing the mortality and morbidity of existing operations. One complication of the closure of ventricular septal defects and endocardial cushion defects is surgical heart block. This complication probably results in a higher mortality than the pre-existing intracardiac defect.
Historically, the conduction mechanism was identified at an early date. Lev1 states that the position and course of the AV node, bundle, and bundle branches in various congenitally abnormal hearts was systematically investigated and found to be in a normal location by Mönckeberg and to a lesser extent by Keith. The early operations for the closure of ventricular septal defects, however, resulted in a high incidence, approximately 12%, of complete heart block.2
Techniques for the surgical closure of ventricular septal defects were modified, perfusion techniques were improved, and the position of the conduction system