Acute efficacy and mid-term clinical outcomes of expandable vs. fixed-size cryoballoon ablation for paroxysmal atrial fibrillation: a two-center randomized study

Background Cryoballoon (CB) pulmonary vein isolation (PVI) is a well-established treatment for paroxysmal atrial fibrillation (PAF). A novel expandable CB was developed to accommodate pulmonary vein anatomical variability, improve vein occlusion, and enable more consistent lesion delivery. However, randomized data comparing it to fixed-sized CB are limited. Purpose To compare acute procedural efficacy and mid-term clinical outcomes of expandable versus fixed-size CB ablation. Methods We conducted an unblinded, prospective, two-center randomized trial enrolling consecutive patients with PAF undergoing first-time CB PVI. Patients were randomized using a simple randomization tool (1:1 ratio) to ablation with an expandable CB (POLARx FIT™, Boston Scientific) or a fixed-size CB (Arctic Front Advance Pro™, Medtronic). Primary efficacy endpoints were acute pulmonary vein isolation and freedom from atrial fibrillation (≥30 seconds) after a 3-month blanking period at 1-year follow-up, assessed by periodic ECGs and 24-hour Holter monitoring. The safety endpoint was a composite of periprocedural complications (including phrenic nerve palsy, pericardial effusion, vascular complications, and stroke/TIA) occurring within 30 days. Results A total of 184 patients were enrolled and randomized (expandable CB: 82; fixed-size CB: 102). Baseline demographic and clinical characteristics were well balanced between the two groups. Acute PVI was achieved in 98.8% vs 97.1% (p = 0.63). Procedural characteristics were similar between groups: median procedure time was 60 minutes in both (IQR: 50–75 vs. 47.75–70; p = 0.307), and median fluoroscopy time was 10.12 minutes (IQR: 5.38–19.08) vs. 10.1 minutes (IQR: 5.4–17; p = 0.808). Freedom from atrial fibrillation at one year was 86.6% in the expandable CB group versus 89.2% in the fixed-size CB group (p = 0.582, log-rank test). Periprocedural complications occurred in 4.9% vs. 1% of patients (p = 0.174). The majority were vascular access site complications, with no cases of persistent phrenic nerve palsy, stroke, or TIA observed. Conclusion In this randomized cohort of patients with PAF, the expandable CB and fixed-size CB demonstrated comparable rates of acute isolation, 1-year freedom from AF, and procedural complications. Although underpowered to detect small differences, these findings do not suggest a clinical advantage of one device over the other, and adequately powered trials are needed to confirm these results.