Cryosurgical ablation of the A V node his bundle. A new method for producing A V block

Abstract

Supraventricular arrhythmias arising at the atrial or junctional level can be disabling or lifethreatening if associated with a rapid ventricular response. Usually, these dysrhythmias can be managed successfully by pharmacologic or pacemaker techniques. In refractory cases, surgical creation of a complete atrioventricular (A-V) block offers another approach to the treatment of such intractable supraventricular arrhythmias. Previous attempts to ablate atrioventricular conduction in clinical and experimental situations have included ligation of tissue near the A-V node, electrocautery of the A-V node His bundle, injection of formalin into the tissue surrounding the His bindle, surgical transection of the His bundle, mechanical crushing, and septal infarction. These interventions have been associated with variable success in achieving permanent ablation of conduction. In some cases tricuspid insufficiency, ventriculo septal defects, and injury to the aortic sinuses have resulted. The purpose of this communication is to describe results of animal and clinical experience with the cryosurgical instrument which was devised to effect a reversible or a permanent A-V block with a stable subsidiary rhythm. The instrument (and the procedure) was used in 20 dogs and subsequently in 3 patients with drug resistant, life threatening supraventricular tachycardias. In the patients, the cryosurgical unit lowered the temperature of the His bindle area to 0°C, effecting complete but reversible heart block. Rewarming resulted in resumption of normal atrioventricular conduction. The His bundle region then was cooled to -60°C; complete heart block was produced with 2 or more 90-120 sec. freezes. Postoperative evaluations revealed a persistent a.v. block. The lesion showed no tendency to rupture, form aneurysm, or interfere with valvular function. In the clinical cases, postoperative studies demonstrated a stable pacemaker arising proximal to the branching portion of the His bundle. A potential application of the cryosurgical technique might be ablation of sites of dysrhythmia (i.e., ectopic foci, re-entry circuits, accessory pathways).