Effects of slow pathway ablation on fast pathway function in patients with atrioventricular nodal reentrant tachycardia: Cryo- vs. radiofrequency ablation

Background: In typical atrioventricular nodal reentrant tachycardia, radiofrequency (RF) ablation of the slow pathway (SP) is known to change the effective refractory period of the fast pathway (ERP _FP) after successful RF ablation of the SP. The purpose of this study was to ascertain the mechanism of the ERP _FP changes after SP ablation by comparing the results of both cryo- and RF ablation. Methods and Results: A total of 112 patients were enrolled prospectively and their electrophysiological properties analyzed before and after successful SP ablation. Patients were grouped into cryoablation (n=54) and RF ablation (n=58) groups and each group was subdivided into complete ablation (CG) and modification (MG) based on the presence of the SP after successful ablation. CG was performed in 64 patients: 30 by cryoablation and 34 by RF ablation. In patients who underwent complete SP ablation, the ERP _FP was shortened significantly after cryoablation (375±74 vs. 281±39 ms, P<0.01), without significant change in the atrio-His (AH) or sinus cycle length (SCL) interval. Similarly, the ERPFP was shortened significantly (358±106 vs. 289±84 ms, P=0.01) also after RF ablation without change in AH or SCL interval. Conclusions: ERP _FP shortening was observed after complete SP ablation with both cryo- and RF ablation without significant changes in indices of autonomic activity.