Electrophysiological Delineation of the Specialized A-V Conduction System in Patients with Congenital Heart Disease

The course of the distal His bundle and the right bundle branch was electrophysiologically delineated during open heart surgery in nine patients with tetralogy of Fallot and in six other patients with various forms of congenital heart disease. In patients with tetralogy of Fallot, right bundle branch electrograms were usually recorded up to 25 mm from the plane of the tricuspid valve annulus and only rarely beyond this site, indicating that the electrical activity in the right bundle branch was isolated from right ventricular myocardium to a site 25 mm away from the tricuspid annulus in the patients studied. In one patient with right bundle branch block pattern on the electrocardiogram induced by a ventriculotomy, the right bundle branch was traced to the Purkinje fiber-ventricular muscle junction, supporting the observation that a right bundle branch block pattern induced by ventriculotomy does not indicate that injury to the proximal part of the right bundle branch occurred. In five patients with various forms of congenital heart disease we did not record electrical activity from the distal His and right bundle branch. The anatomic and functional reasons for this failure are discussed. In one patient with a common ventricle, the identification of the specialized atrioventricular (A-V) conduction system allowed for total surgical correction of this anomaly without injury to the conduction system. The electrophysiological delineation of the specialized atrioventricular conduction system is suggested for all patients undergoing open heart surgery who have complicated congenital heart disease on which no data are available regarding the exact location of the specialized atrioventricular conduction system, for patients with unusual ventricular anatomy, and for patients in whom the hemodynamic and angiographic studies do not correlate well with the electrocardiogram.