An electrophysiologic technique has been described to localize the atrioventricular (A-V) conduction system during cardiac surgery. The method utilizes atrial pacing with an electrode plaque to insure a supraventricular rhythm, and an electrode probe to localize the specialized A-V pathways. Atrial pacing assures unchanging antegrade conduction to the ventricles, which permits beat-to-beat observation of changes in the P-R interval or QRS configuration that might result from surgical manipulation. The anatomic course of the His bundle and bundle branches is delineated by observing a typical "His spike" during the P-R interval in the electrogram. While heart block is uncommon following repair of uncomplicated ventricular septal defect, this technique has been a distinct aid in the repair of ostium primum atrial septal defects (four cases) and fourteen other complex congenital anomalies.
Kaiser GA, Waldo AL, Beach PM, Bowman FO, Hoffman BF, Malm JR. Specialized Cardiac Conduction SystemImproved Electrophysiologic Identification Technique at Surgery. Arch Surg. 1970;101(6):673-676. doi:10.1001/archsurg.1970.01340300029006