The present study describes a surgical method for the permanent prolongation of atrioventricular (AV) conduction. In 22 dogs, a series of 9 discrete cryolesions were placed along the perimeter of the triangle of Koch while the His bundle electrogram was being monitored continuously. Ten dogs underwent a sham operation to control for the effects of cardiopulmonary bypass and atriotomy on AV conduction. The conduction time through the AV nodal region was significantly (p < 0.01) prolonged acutely (3 hours postoperatively) and chronically (14 weeks postoperatively) in the animals subjected to cryosurgery. Thus selective cryosurgery in the AV nodal region produces a permanent alteration in AV conduction. This cryosurgical technique may result in ablation of the electrophysiological substrate required for paroxysmal supraventricular tachycardia resulting from AV nodal reentry.
