The conduction system in simple, regular (D-), complete transposition with ventricular septal defect.

This is a serial section study of the conduction system in 5 cases of complete (d-) transposition with ventricular septal defect (VSD) . In 3 of the cases with infracristal or intracristal VSD, the bundle lay in the posterior (inferior) wall on the left side of the defect. In the fourth case with infracristal VSD it was on the right side of this wall. In the case with a more distally situated VSD, the bundle branches skirted the anterior and distal walls of the defect. This study shows that in closure of the VSD in complete transposition, the posterior wall of the defect in some cases, and in others the anterior and distal walls of the defect are to be handled judiciously. The right side of this wall is probably safer to handle from the standpoint of block than the left side in most cases. His bundle recording during open-heart surgery may be indicated in large or unusually located VSD's to delineate the course of the conduction system and thereby to avoid atrioventricular (A-V) block.