Safety of Slow Pathway Ablation in Patients With Atrioventricular Node Reentrant Tachycardia and a Long Fast Pathway Effective Refractory Period

Abstract

Radiofrequency catheter ablation is an accepted primary therapy for atrioventricular (AV) node reentrant tachycardia (AVNRT). There is concern that slow pathway ablation in patients with a long anterograde fast pathway effective refractory period (ERP) may potentially impair subsequent node conduction. Eighteen patients (14 women; age 53 ± 20 years) with symptomatic AVNRT, whose fast pathway ERP at baseline was ≥500 ms, underwent slow pathway ablation. Their outcome was compared with 24 consecutive control patients (17 women; age 42 ± 17 years) who underwent ablation for AVNRT whose fast pathway ERP at baseline was <500 ms (controls). Slow pathway ablation was successful in 16 patients (90%). One patient had inadvertent fast pathway ablation. In a second patient the slow pathway could not be ablated because of recurrent transient AV block. Ablation was successful in all patients in the control group. Transient AV block related to current application occurred in 4 patients (22%) versus 1 control (4%) (p = 0.07). After ablation, the AV node refractory period increased in patients (368 ± 68 to 428 ± 92 ms, p = 0.02) and in controls (282 ± 35 to 336 ± 55 ms, p <0.0001), but the fast pathway ERP shortened in both groups (patients: 558 ± 63 to 428 ± 92 ms, p = 0.003; controls: 356 ± 53 to 336 ± 55 ms, p = 0.05). Furthermore, the slope of the regression line relating to shortening of the fast pathway ERP to the baseline ERP was markedly steeper in patients compared with controls (1.9 vs 0.4, p <0.0001). The shortening of the fast pathway ERP was greater in patients compared with controls (122 ± 130 vs 21 ± 50 ms, p = 0.001). During a mean follow-up of 18 ± 11 months, 1 patient with severe coronary artery disease died suddenly 2 years after ablation. There was no recurrence of clinical tachycardia, and none of the patients developed symptoms of bradycardia or required permanent pacing. Thus, slow pathway ablation in patients with AVNRT and a long fast pathway ERP is safe and effective.