Etiology of right bundle branch block pattern following surgical repair of atrioventricular cushion defects.

Electrocardiograms and surgical data from 12 patients with complete atrioventricular canal defects and 24 patients with ostium primum defects were evaluated before and after open heart surgery in order to document the incidence of postoperative right bundle branch block. The use and precise location of septal sutures utilized for repair were specifically noted in order to assess their possible role in the genesis of the postoperative right bundle branch block pattern. Septal sutures were placed in all patients with atrioventricular canal defects, and ten (83 percent) of these 12 patients developed right bundle branch block. Seven (29 percent) of the 24 patients with ostium primum defects developed a postoperative right bundle branch block, and in all seven patients, septal sutures were utilized. None of the patients with an ostium primum defect without septal sutures developed a right bundle branch block, and none of the patients in this series developed complete heart block.