BACKGROUND: Cryoballoon ablation is less operator-dependent than radiofrequency ablation. Recently, size-adjustable cryoballoons (SA-CBs) have become available. We sought to analyze the individual baseline operator experience's impact on procedural results. METHODS: This multicenter observational study included atrial fibrillation (AF) patients who underwent pulmonary vein (PV) isolation using SA-CBs capable of 28-mm or 31-mm balloon sizes. Experienced (E-group) or less experienced (LE-group) operators were defined as experiencing >
100 or ≤ 100 cryoballoon procedures, respectively. RESULTS: Among 510 patients (67 ± 11 years, 355 men, 325 paroxysmal AF [PAF]) who underwent an SA-CB ablation, 240 and 270 were in the E-group and LE-group, respectively. All cryoballoon parameters were similar between the groups, except for a significantly higher 31-mm balloon isolation rate in the E-group than LE-group, especially for right superior PVs. Cryoballoon-related phrenic nerve injury occurred in 34 (6.7%) patients and tended to be higher in the LE-group than E-group (8.1% vs. 5.0%, p = 0.16). The AF freedom was comparable between the groups for both PAF and non-PAF patients. A total of 36(7.1%) patients underwent re-do procedures at 5.2 ± 2.6 months post-index procedure. The PV reconnection rate was significantly higher in the LE-group than E-group (27.1% vs. 8.9%, p <
0.01), and this trend was more pronounced for right PVs than left PVs. CONCLUSIONS: In AF ablation using SA-CBs, the overall procedural efficacy and safety were comparable between the E-group and LE-group. However, 100 CB procedures seemed to still be in the middle of a learning curve for selecting the balloon size and balloon position, especially for right PVs.