Late Postoperative Conduction Disturbances After Repair of Ventricular Septal Defect and Tetralogy of Fallot

Abstract

His bundle electrograms were recorded in five children who developed complete heart block (CHB) five months to five years after cardiac surgery. In four children who had an electrocardiographic pattern of right bundle branch block and left axis deviation (RBBB and LAD) preceding the appearance of CHB, the site of block was distal to the area generating the His potential. The fifth child, who had an electrocardiographic pattern of RBBB with normal axis prior to the development of CHB, had block occurring proximal to the area generating His potential. All five children had had transient CHB in the immediate postoperative period. In an additional 17 postoperative patients, His bundle recordings were obtained during sinus rhythm. Five out of ten patients with RBBB and LAD on the electrocardiogram and one patient with LBBB had H-V interval prolongation, a recording suggesting incomplete bilateral bundle branch block or trifascicular block. Six patients with RBBB only on the electrocardiogram had normal H-V intervals. All the patients with H-V interval prolongation had had CHB transiently in the immediate postoperative period. This study suggests that patients with an electrocardiographic pattern of RBBB and LAD who have had transient CHB postoperatively may have, more extensive residual damage to the conduction system than suspected on the basis of the surface electrocardiogram alone and because of the risk of late recurrence of CHB should be given a guarded prognosis.