Background:
Cryoballoon (CB)-guided pulmonary vein isolation (PVI) represents the cornerstone in the treatment of atrial fibrillation (AF). In addition to the established AFA CB ablation system (Arctic Front Advance Pro, AFA, Medtronic), a novel balloon-guided single shot device (POLARx, Boston Scientific) for PVI was designed. 

Objectives:
Aim of this observational single center study was to evaluate ablation efficacy and outcome using the novel POLARx CB system compared to the established AFA system and to access the impact of the individual PV anatomy on freedom from arrhythmia recurrence.

Methods:
A total number of 596 patients treated with CB-guided ablation for AF were included. 65 consecutive patients undergoing ablation with the POLARx were compared to a cohort of 531 patients treated with AFA. Pre-procedural cardiac magnetic resonance imaging (MRI) was performed to assess individual anatomical characteristics of the left atrium and PVs. For each PV, the cross-sectional orifice area (CSOA) was determined. Follow-up examinations were scheduled after 3 and 6 months.

Results:
Acute PVI was achieved in all patients (n=596, 100%). AF-free survival rates were significantly higher in the POLARx group compared to patients from the AFA group (POLARx, n=20, 31%; AFA, n=208, 39%; p=0.049*). In both groups, MRI revealed a comparable percentage of patients with normal PV anatomy (2 left- and two right-sided PVs) (p=0.141). Variant PV anatomy was identified in 65 AFA treated patients (12%) and in 8 POLARx patients (12%) (left common ostium: POLARx, n=4, 6%; AFA, n=51, 10%; right sided accessory vein: POLARx, n=4, 6%; AFA, n=8, 2%; right common ostium: AFA, n=6, 1%). Left sided pulmonary vein CSOA differed significantly between POLARx and AFA group patients (LSPV: POLARx, 190.2±60.8 mm2; AFA, 226.9±69.7 mm2, p<0.001*; LIPV: POLARx, 178.2±47.0 mm2; AFA, 149.2±60.5 mm2, p<0.001*). Concerning the suspected PV-occlusion rate and thus the efficacy of PVI no significant CSOA differences were observed in POLARx group patients with AF recurrence compared to those without. Similar results were calculated for AFA patients. Beyond that, in both groups (POLARx and AFA) variant PV anatomy was not predictive for AF recurrence.

Conclusion:
PVI using the POLARx system improves freedom from AF recurrence compared to previous single-shot ablation devices. This observation was independent of individual anatomical considerations and PV occlusion rates. Further studies are required to confirm this initial observation.