Modification of Atrioventricular Conduction Using a Combined Laser-Electrode Catheter ANNE B. CURTIS, MICHAEL MANSOUR, STEPHAN E. FRIEDL,* TAKANOBU TOMARU,** GERALD R. BARBEAU.t SIGURD J. NORMANN, and GEORGE S. ABELA* From the Departments of Medicine and Pathology, University of Florida, and the Gainesville Veterans Administration Medical Center, Gainesville, Florida; and the *Department of Medicine, Harvard Medical School and the Deaconess Hospital. Boston. Massachusetts; and the **Second Department of Medicine, University of Tokyo, Tokyo, Japan; and the tDepartment of Medicine, Laval University, Quebec, Canada CURTIS, A.B., ETAL.: Modification of Atrioventricular Conduction Using a Combined Laser-Electrode Catheter. Ablation of the AV junction is an accepted technique for the management of selected supraven- tricular tachyarrhythmias. Radiofrequency ablation appears to be safe and effective for AV junction abla- tion in most patients, but the need for firm tissuecontact may make it less effective for ventricular tachycar- dia and certain ectopic atrial tachycardias. Laser energy can also be delivered through a catheter, and thus it may be an attractive alternative energy source for ablation. A new laser-electrode catheter was developed for modification of conduction through the AV node as a model for ablation of an arrhythmia substrate. A window for delivery of continuous-wave Nd:YAC laser energy was placed between the two electrodes of a bipolar electrode catheter. In vitro studies using a matrix of power versus time were per- formed to determine the energy that would create lesions of the appropriate size in vivo. Using this information, advanced AV block was successfully created in 16 of 17 dogs (94%) with the laser-electrode catheter. Advanced AV block was successfully created in all four dogs in the chronic study, and it persisted for 1-24 weeks of follow-up until sacrifice of the animals. Histologic examination demonstrated discrete thermal damage at the AV junction with no instances of septal perforation in the acute studies or progres- sive necrosis in chronically maintained dogs. Advanced AV block may be produced consistently and safely in dogs using a combined laser-electrode catheter. (PACE, Vol. 17, March 1994, Part I) atrioventricular node, laser, ablation, supraventricular tachycardia This study was supported in part by grants-in-aid from the American Heart Association, Central Florida Affiliate, the Flor- ida High Technology and Industry Council, Tallahassee. Flor- ida, and the National Institutes of Health, Bethesda, Maryland (RO1-HL30320 and R43-HL44273}, Dr. Ahela and S.K. Friedl hold executive positions and arR entitled to royalties from Aheta Laser Sysfems, Fresented as an abstract at the American College of Cardiology, New Orleans, Louisiana, March. 1990, Address for reprints: Anne B. Curtis, M.D.. Division of Cardiol- ogy, University of Florida, Box 100277. Gainesville. FL 32610. Fax: (904) 371-0370, Received January 26,1993; revision June 15,1993; revision July 31, 1993; accepted September 27, 1993. Introduction Transvenous catheter ablation of the atrioven- tricular [AV) junction has become an accepted method of treatment for selected patients with sn- praventricular tachyarrhythmias.'"'' Although AV nodal ablation was first accomplished surgically, the catheter technique has an eqnal success rate with lower morbidity, mortality, and cost.^^ Cathe- ter ablation of the AV junction has become the pre- ferred mode of therapy for patients with atriai fi- brillation who have failed to respond to or have been intolerant of pharmacological therapy. PACE, Vol, 17 March 1994, Part I 337