RADIOFREQUENCY CATHETER ATRIOVENTRICULAR NODE ABLATION IN PATIENTS WITH PERMANENT CARDIAC PACING SYSTEMS

Following successful RF ablation of the atrioventricular node IA (AVN) , temporary pacing is necessary prior to insertion of a permanent pace maker. The risks and inconvenience of temporary pacing could be avoide d if a permanent pacemaker is already in place. This study reports the feasibility of RF ablation of the AVN in 27 patients (age 55 +/- 17 y ears, 15 males) with hypertrophic cardiomyopathy and pacemakers. Indic ations for AVN ablation were drug refractory atrial fibrillation in 24 patients, and rapid AVN conduction preventing septal pre-excitation b y DDD pacemaker, inserted for relief of left ventricular outflow obstr uction, in three cases. Sixteen patients had DDD devices and 11 patien ts had WI devices. During RF ablation, each pacemaker was programmed t o WI at 50 beats/min. The ablation catheter was manipulated with fluor oscopic control to avoid close contact with or disturbance of the paci ng leads. In 16 patients, RF ablation was performed immediately follow ing pacemaker implantation but in the remaining patients, the AVN was ablated 6-32 months after pacemaker implantation. The power applied wa s 25-50 watts for a duration of 15-60 seconds. AV block was achieved i n all cases but required 34 +/- 36 applications for 16.5 +/- 17.8 min/ case. RF ablation consistently caused reversion to magnet rate in one patient and temporarily inhibited appropriate pacemaker discharge in a nother. However, no other pacemaker or lead malfunction was detected s o that temporary pacing wets not required in any case. At 6 +/- 3 mont hs follow-up, all pacemakers were functioning normally without alterat ion in pacing parameters from baseline. Thus, RF ablation of the AVN c an be performed safely in the presence of a recently implanted permane nt pacemaker, without temporary pacing.