The "window" of slow pathway conduction after ablation and recurrence of atrioventricular nodal reentrant tachycardia.

INTRODUCTION: Slow pathway (SP) conduction often persists following radiofrequency (RF) catheter ablation of atrioventricular nodal reentrant tachycardia (AVNRT). An association between persistent SP conduction, as evidenced by discontinuous AV nodal conduction curves, and recurrent tachycardia has not been established. Of note, the segment of the curve attributable to SP conduction (the "window" of SP conduction) varies. This study examined whether the maximal post-ablation SP conduction window length differs in patients who later have recurrent tachycardia when compared with those who do not recur. METHODS AND
RESULTS: Electrophysiologic study data were compared in two groups who had undergone RF ablation of the SP for typical AVNRT at a single center from 1992-1998. The groups, consisting of seven known recurrences (Group A) and 50 non-recurrences confirmed through a follow-up survey and phone contact (Group B), were similar in gender proportion, age, baseline electrophysiologic data, and number of RF deliveries. Four patients (57%) from Group A and 26 (52%) from Group B exhibited discontinuous AV nodal conduction curves after ablation. The maximum post-ablation window lengths among patients with dual AV nodal physiology varied widely and similarly in the two groups, and the means did not significantly differ (53 +/- 47 msec in Group A vs. 36 +/- 31 msec in Group B; p=0.36).
CONCLUSION: Persistent SP conduction post-ablation in this series was a common finding not predictive of recurrence. No difference in the maximum SP conduction window post-ablation was evident between recurrences and non-recurrences.