BackgroundResidual slow pathway conduction in the form of persistent jump in the atrioventricular (AV) conduction time or atrial echo beats is a common finding after successful radiofrequency (RF) ablation of the slow pathway in patients with AV nodal reentrant tachycardia (AVNRT). Sites of successful RF ablation of the slow pathway may be located anteriorly in the tricuspid annulus (cephalad to the coronary sinus os) or posteriorly (at, within, or caudal to the coronary sinus os). The aim of this study was to investigate whether arrhythmia recurrences correlate with persistent slow pathway conduction or site of successful ablation.Methods and ResultsAmong 55 patients with symptomatic AVNRT having RF ablation, 23 patients (42%) (group 1) had evidence of persistent dual AV nodal pathway physiology and/or echo beats, whereas in 32 patients (group 2), slow pathway conduction had been completely eliminated. With regard to ablation sites, 14 patients (25%) (group A) had their slow pathway successfully ablated at an inferoposterior site, whereas in 41 patients (group B), the ablation site was located anteriorly to the coronary sinus os. The study patients included 17 men and 38 women, aged 37 ± 18 years. The electrophysiological study and RF ablation were performed in a single session in 50 patients (91%). After the first session, the technique was successful in all patients (100%), with elimination of AVNRT and without affecting AV conduction. A mean of 9 ± 6 lesions were applied. The total procedure time averaged 4 ± 1 hours. Fluoroscopy time was 41 ± 25 minutes. Except for transient AV block in 1 patient, no other complications occurred. Over 12 ± 8 months, a total of 7 patients (13%) had recurrence of AVNRT, and 6 of them underwent successful repeat slow pathway RF ablation. Recurrence rate was 9% (2 patients) for group 1, with persistent jump or echo beats, and 16% (5 patients) for group 2, without residual slow pathway conduction (P= NS). Five of the recurrences (71%) were noted in group A and 2 in group B. Thus, the recurrence rate was 36% for group A (5 of 14 patients), with posterior ablations, and 5% for group B (2 of 41 patients), with anterior sites of successful RF ablation (P< .05).ConclusionsAfter successful RF ablation of the slow pathway in patients with AVNRT, residual slow pathway conduction does not correlate with clinical tachycardia recurrences. However, the site of successful RF ablation of the slow pathway does correlate with arrhythmia recurrences. More recurrences are observed when the site is located inferoposteriorly, at or below the os of the coronary sinus, as compared with medial and anterior locations of the ablation site.