Histologic observations of the cardiac conduction system in a patient with postoperative bilateral bundle branch block

Abstract

It has been suggested that the postoperative development of a right bundle branch block pattern is due to injury of peripheral rather than proximal parts of the right bundle branch and does not affect the prognosis for the later development of complete heart block. However, the occurrence of complete heart block in a patient with postoperative right bundle branch block who later has left bundle branch block has not previously been documented. The entire specialized cardiac conduction system of a patient who had two operations for repair of double outlet right ventricle and multiple ventricular septal defects was serially sectioned. In the first operation, which resulted in a right branch block pattern, a subaortic ventricular septal defect was repaired through a right ventriculotomy. In the second operation complete heart block occurred after multiple muscular ventricular septal defects were repaired with a patch inserted through a left ventriculotomy. Examination of the conduction system showed that the right bundle branch was completely interrupted by the patch used to repair the subaortic ventricular septal defect and the left bundle branch was completely severed by the patch used to repair the muscular ventricular septal defects. This case proves that some patients who have a right bundle branch block pattern after repair of a ventricular septal defect may later have complete heart block if left bundle branch block develops as a result of sclerodegenerative or atherosclerotic heart disease or other cause.