Electrophysiological determinants of persistent dual atrioventricular nodal pathway physiology after slow pathway ablation in atrioventricular nodal reentrant tachycardia

The purpose of this study was to examine the electrophysiological determina nts of the elimination of recurrent atrioventricular nodal reentrant tachyc ardia (AVNRT) despite the persistence of dual AV nodal pathway physiology o r single echo beats after ablation procedures. The study included 26 patien ts with common AVNRT who had undergone successful ablation treatment and no long-term recurrence of AVNRT. The slow pathway potential was targeted, an d the endpoint of ablation was one echo during atrial extrastimulus testing (ET) with isoproterenol. persistent dual pathways physiology or single ech oes were present in 12 patients (group I) and absent in 16 (group II) after ablation. The number of anterograde AV nodal pathways and maximum AH inter val (Max AH) during ET were measured before and after ablation, and ventric uloatrial conduction during ventricular pacing was examined. Results: (1) m ultiple AV nodal pathways were more frequently observed in group I than in group II (50.0% vs 7%, P < 0.05); (2) Max API decreased significantly after ablation in both groups (309 +/- 157 vs 171 +/- 53 ms in group II; P < 0.0 1, and 409 +/- 65 vs 274 +/- 86 ms in group I; P < 0.001); and (3) retrogra de dual pathway conduction was more common in group I than in group II. The se data suggest the presence of nonuniform conductive properties of the AV node in group I and that ablation targeting the slow pathway potential prev ents recurrences of AVNRT by eliminating the pathway with the longest condu ction time.