Therapy and Prevention Cryosurgery

Paroxysmal supraventricular tachycardia most commonly arises from reentry within the atrioventricular (AV) node. Although ablation of the His bundle has gained popularity for treating patients with AV node reentrant tachycardia refractory to medical therapy, undesirable sequelae include complete heart block and the necessity for a permanent pacemaker. To obviate this limitation, we have developed a discrete cryosurgical procedure that interrupts the reentrant circuit responsible for AV node reentrant tachycardia without blocking AV conduction. After first characterizing the salutary effects of this approach in experimental animals, we performed this procedure in eight patients with AV node reentrant tachycardia. Preoperative, intraoperative, and postoperative electrophysiologic studies were performed in each patient. Under conditions ofnormothermic cardiopulmonary bypass and during atrial pacing at a constant rate with continuous monitoring ofAV conduction, nine separate 3 mm cryolesions (-60o C for 2 min) were placed at predetermined sites around the triangle of Koch in the lower right atrial septum. Postoperatively, each patient had a single AV node conduction curve. No patient had AV node reentrant tachycardia induced or has experienced AV node reentrant tachycardia clinically during a follow-up of up to 5 years. The cryosurgical procedure had no detrimental effects on the AH or HV interval or on the paced cycle length at which AV node Wenckebach occurred. Based on these results, this curative operation offers promise for patients with AV node reentrant tachycardia that is refractory to medical treatment. Circulation 76, No. 6, 1329-1336, 1987. PAROXYSMAL supraventricular tachycardia most commonly arises from reentry within the atrioventricular (AV) node.14 Before 1981, the only effective surgical treatment for medically refractory AV node reentrant tachycardia was surgical ablation of the His bundle.5 In 1982, Scheinman et al.6 demonstrated the feasibility of ablating the His bundle by passing an electric shock through a standard His bundle catheter. Although catheter ablation ofthe His bundle has gained popularity because it precludes the need for an open heart operation, undesirable side effects of the procedure are complete heart block and the necessity for a permanent pacemaker system. From the Division of Cardiothoracic Surgery, Department of Surgery, and the Division of Cardiology, Department of Medicine, Washington University School of Medicine, Barnes Hospital, St. Louis. Supported by NIH grant number ROI-HL 32257 and in part by NIH grant number HL-17646, SCOR in Ischemic Heart Disease. Address for correspondence: James L. Cox, M.D., Professor of Surgery, Chief, Division of Cardiothoracic Surgery, Washington University Medical Center, 4989 Barnes Hospital Plaza, Suite 3108, St. Louis, MO 63110. Received April 1, 1987; revision accepted Aug. 27, 1987. *All editorial decisions for this article, including selection of reviewers and the final disposition, were made by a guest editor. This procedure applies to all manuscripts with authors from the Washington University School of Medicine. Vol. 76, No. 6, December 1987 Because ablation of the His bundle replaces one problem (tachycardia) with another (heart block), we developed and tested a surgical technique capable of interrupting the reentrant circuit responsible for AV node reentry tachycardia without blocking normal AV conduction. In 1982, we reported that multiple discrete (3 mm) cryolesions placed around the triangle of Koch were capable of altering the input pathways of the AV node, resulting in permanent prolongation of AV conduction in experimental animals.7 Subsequent studies documented that in the presence of dual AV node conduction pathways, this discrete cryosurgical procedure was capable of selectively ablating only one of the pathways of conduction, thereby leaving normal AV conduction intact while interrupting the anatomicelectrophysiologic substrate responsible for AV node reentrant tachycardia.'10 After first developing and characterizing the salutary effects of this approach in experimental animals, we applied the procedure in patients with AV node reentrant tachycardia. This communication describes the clinical characteristics of this group of patients, the surgical technique used for the treatment of AV node reentrant tachycardia, and the results of surgery. 1329 by gest on A ril 3, 2017 http://ciajournals.org/ D ow nladed from