SLOW PATHWAY ABLATION IN PATIENTS WITH ATRIOVENTRICULAR NODE REENTRANT TACHYCARDIA AND A PROLONGED PR INTERVAL

Objectives. We sought to assess the safety and efficacy of selective s low pathway ablation using radiofrequency energy and a transcatheter t echnique in patients with a prolonged PR interval and atrioventricular (AV) node reentrant tachycardia. Background. Although both fast and s low AV node pathways can be ablated in patients with AV node reentrant tachycardia, slow pathway ablation, by obviating the risk of AV block , appears to be safer. However, the safety and efficacy of selective s low pathway ablation using transcatheter radiofrequency energy in pati ents with a prolonged PR interval during sinus rhythm are unclear. Met hods. The seven study patients with a prolonged PR interval (mean +/- SD 237 +/- 26 ms) comprised three women and four men with a mean age o f 31 +/- 15 years. The slow pathway was targeted in all seven patients at the posterior/inferior interatrial septal aspect of the tricuspid annulus. Two patients presented with the uncommon variety of AV node r eentrant tachycardia after initial fast pathway ablation; in the remai ning five patients, the AV node reentrant tachycardia was of the commo n variety. Results. A single radiofrequency pulse at 30 W successfully abolished the slow pathway in both the anterograde and the retrograde direction in the two patients with uncommon AV node reentrant tachyca rdia. A mean of 5 +/- 3 radiofrequency pulses were required in the rem aining five patients with reentrant tachycardia of the common variety. The postablation PR interval and AH interval remained unchanged. The shortest cycle length of 1:1 AV conduction was prolonged significantly (from 327 +/- 31 to 440 +/- 59 ms, p < 0.01, as was the AV node effec tive refractory period (from 244 +/- 35 to 344 +/- 43 ms, p < 0.01). D uring a mean follow-up interval of 20 +/- 6 months, no patient develop ed symptoms suggestive of AV node reentrant tachycardia or had evidenc e of second- or third-degree AV block. Conclusions. These data suggest that the AV node slow pathway can be ablated in patients with AV node reentrant tachycardia who demonstrate a prolonged PR interval during sinus rhythm.