All consecutive patients with paroxysmal or persistent atrial fibrillation undergoing pulmonary vein isolation with the radiofrequency balloon catheter (RFB) "Heliostar" (Biosense Webster) will be included in a multicenter observational registry. The aim of the study is to assess the safety and arrhythmic outcome of atrial fibrillation ablation with the RFB in a real-world setting.

All consecutive atrial fibrillation patients undergoing pulmonary vein isolation (PVI) with the novel radiofrequency balloon catheter (RFB) "Heliostar" (Biosense Webster) will be prospectively included in a multicenter observational registry.

PVI with the RFB will be performed as previously described. Briefly, after optimal RFB positioning, confirmed through the correct alignment between the RFB and the pulmonary vein and sufficient electrode-tissue contact, ablation is performed in temperature-controlled mode with unipolar radiofrequency energy. Typically, >2 posterior electrodes are identified on the RFB. The power setting is 15 W and the target electrode temperature is 55° C. The same energy is simultaneously delivered to all electrodes, with a duration of 15-20 s for the posterior and 45-60 s for the non-posterior electrodes. During ablation, pulmonary vein potentials are monitored on the circular diagnostic catheter to evaluate real-time isolation. In the case of pulmonary vein acute reconnection, additional applications are delivered to achieve durable PVI. An esophageal temperature probe will be used to monitor any increase in esophageal temperature.

Follow-up will be performed according to each standard institutional protocol.

Safety endpoints include any major periprocedural complications [e.g. death, atrioesophageal fistula, stroke/transient ischaemic attack, pericardial effusion/tamponade with/without surgical treatment, myocardial infarction, and persistent phrenic palsy] occurring within 7 days post-procedure (except for atrioesophageal fistula). Minor complications will also be reported, including vascular access complications requiring treatment, pericarditis, and transient phrenic palsy.

Efficacy outcome is defined as arrhythmia-free survival during the follow-up. Arrhythmia recurrence is defined as any atrial tachyarrhythmias ≥30 s after a 90-day post-ablation blanking period.

Inclusion Criteria:

• symptomatic atrial fibrillation with indication to catheter ablation

Exclusion Criteria:

• age <18 years old
• pregnancy
• any contraindications to catheter ablation

All consecutive patients with symptomatic paroxysmal or persistent atrial fibrillation undergoing a first-time pulmonary vein isolation with the multielectrode radiofrequency balloon catheter (HELIOSTAR, Biosense Webster, CA, USA) will be prospectively included.