Characteristics of atrioventricular block during slow pathway ablation for atrioventricular nodal re‐entrant tachycardia: A comparative study of cryoablation and radiofrequency ablation

Introduction Slow‐pathway ablation with cryoablation is a useful tool for treating atrioventricular nodal re‐entrant tachycardia (AVNRT). However, reports on the characteristics of atrioventricular block (AVB) during cryoablation are limited. Therefore, we investigated the differences in the appearance of AVB between cryoablation and radiofrequency ablation (RFA). Methods This dual‐center retrospective study included 341 patients who underwent slow‐pathway ablation of AVNRT using cryoablation or RFA. Results A total of 137 patients underwent cryoablation (CRYO group, n = 137), and 204 underwent RFA (RF group, n = 204). Transient AVB during slow‐pathway ablation occurred in 33 patients (24.1%) in the CRYO group and 13 patients (6.4%) in the RF group. The time from the beginning of the P‐R interval prolongation to the occurrence of second‐ or third‐degree AVB was significantly longer in the CRYO group (6.6 ± 3.7 s) compared to the RF group (1.2 ± 0.3 s, p < 0.01). Three patients in the RF group developed complete AVB requiring pacemaker implantation, whereas none of the patients in the CRYO group developed permanent AVB. After a median follow‐up of 221 ± 186 days, AVNRT recurred in 13 patients (9.5%) in the CRYO group and in 7 patients (3.4%) in the RF group ( p < 0.01). Conclusion Cryoablation gradually induces atrioventricular conduction disturbances when AVB occurs inadvertently, taking longer than RFA. Compared to RFA, cryoablation has a relatively high incidence of transient AVB during slow‐pathway ablation but does not result in permanent AVB.