Localization and Spread of Challenging Conduction Gaps of Pulmonary Veins for Atrial Fibrillation Cryoablation

Background: Cryoballoon ablation has been widely performed in patients with paroxysmal atrial fibrillation (AF). In some challenging pulmonary veins (PVs), the procedure requires additional touch-up applications against the residual conduction gaps. It implies that there could exist difficult sites to cover with standard cryoballoon applications (CBAs), resulting in resistant conduction gaps (RCGs). This study aims to characterize the RCGs after initial CBAs.

Methods: We retrospectively enrolled 90 consecutive paroxysmal AF patients in our institute from January 2018 to December 2021 (66.5 ± 8.9 [SD] year-old, male/female 58/32). The RCGs after initial CBAs were mapped and analyzed with a high-resolution mapping (HRM) catheter. The PVs isolated using HRM were classified as HRM group. The PVs isolated without HRM, if isolated with a total of one or two CBAs, were classified as Control group.

Results: Whereas 325 PVs were isolated without HRM, 29 PVs had RCGs which were mapped and identified with HRM (HRM group): 15 right inferior pulmonary veins (RIPVs), 11 left superior PVs (LSPVs), and 3 left inferior PVs (LIPVs). In HRM group, the rate of broad RCGs in each PV extending over 2 or 3 segments of PV was almost double that of one-segment RCGs. The width of RCGs significantly correlated with nadir balloon temperature (R = 0.42; p = 0.021) and iTT₁₅ (R = -0.44; p = 0.015).

Conclusions: After standard CBAs, most RCGs were demonstrated to spread from the bottom to the posterior wall of RIPV and from the roof to the anterior wall of LSPV. The width of the RCGs was found to be correlated with parameters of balloon temperature, such as T_nadir and iTT₁₅.