Lukas Urbanek, Boris Schmidt, Stefano Bordignon, David Schaack, Ramin Ebrahimi, Shota Tohoku, Jun Hirokami, Tolga H. Efe, Karin Plank, Britta Schulte‐Hahn, Bernd Nowak, Julian K. R. Chun, Shaojie Chen

• Background Management of atrial fibrillation (AF) in very severe obese patients is challenging. Cryoballoon ablation (CBA) represents an effective rhythm control strategy. However, data in this patient group were limited. Methods Highly symptomatic AF patients with body mass index (BMI) ≥ 40 kg/m2 who had failed antiarrhythmic drug therapy and electrocardioversion and failure to achieve targeted body‐weight‐reduction underwent CBA. Results Data of 72 very severe obese AF patients (Group A) and 129 AF patients with normal BMI (Group B, BMI &lt; 25 kg/m2) were consecutively collected. Group A had significantly younger age (60.6 ± 10.4 vs. 69.2 ± 11.2 years), higher BMI (44.3 ± 4.3 vs. 22.5 ± 1.6 kg/m2). Procedural pulmonary vein isolation (PVI) was successful in all patients (2 touch‐up ablation in Group A). Compared to Group B, Group A had similar procedural (61.3 ± 22.6 vs. 57.5 ± 19 min), similar fluoroscopy time (10.1 ± 5.5 vs. 9.2 ± 4.8 min) but significantly higher radiation dose (2852 ± 2095 vs. 884 ± 732 µGym2). We observed similar rates of real‐time‐isolation (78.6% vs. 78.5%), single‐shot‐isolation (86.5% vs. 88.8%), but significantly longer time‐to‐sustained‐isolation (53.5 ± 33 vs. 43.2 ± 25 s). There was significantly higher rate of puncture‐site‐complication (6.9% vs. 1.6%) in Group A. One‐year clinical success in paroxysmal AF was (Group A: 69.4% vs. Group B: 80.2%; p < .001), in persistent AF was (Group A: 58.1% vs. Group B: 62.8%; p = .889). In Re‐Do procedures Group A had a numerically lower PVI durability (75.0% vs. 83.6%, p = .089). Conclusion For very severe obese AF patients, CBA appears feasible, leads to relatively good clinical outcome.