Management of Patients following Correction of Tetralogy of Fallot and Ventricular Septal Defect

Abstract

In a recent review article, Dr. Krongrad discussed the management of patients with intraventricular conduction defects developing after repair of tetralogy of Fallot or ventricular septal defect (Chest 1984; 85:107-13). It was pointed out that the group of patients who developed late complete heart block includes a disproportionate number whose standard electrocardiogram shows the pattern of right bundle branch block, left axis deviation and PR prolongation. However, if clinicians rely on the presence of these three features of the standard electrocardiogram to identify patients at risk for late complete heart block, then some high risk patients would be overlooked. Presumably the PR prolongation is the result of a prolonged HV interval, indicative of conduction abnormality distal to the His bundle and of increased likelihood of late surgical block; the usual site of surgical complete heart block, early or late, is distal to the His bundle. Since prolonged HV interval may occur with a normal PR interval, 1 Pahlajani DB Serratto M Mehta A Miller RA Hastreiter A Rosen KM Surgical bifascicular block. Circulation. 1975; 52: 82-87 Crossref PubMed Scopus (14) Google Scholar the PR interval may be less definitive than the HV interval in identifying the high risk group. Dr. Krongrad has previously reported 2 Krongrad E Prognosis for patients with congenital heart disease and post-operative intraventricular conduction defects. Circulation. 1978; 57: 867-870 Crossref PubMed Scopus (91) Google Scholar the potential usefulness of measuring HV interval, which can now be done noninvasively. I believe a better appraisal of the risk of late postoperative complete heart block would be obtained if such electrophysiologic investigation was included in the management at least of patients with the pattern of right bundle branch block and left axis deviation whether or not the PR interval is prolonged.