The relationship between exercise and atrial fibrillation (AF) seems to follow a J-shaped curve: while moderate activity reduces AF risk, both insufficient and excessive endurance exercise increase susceptibility. In athletes, standard treatments such as antiarrhythmic drugs often provide only partial symptom control and may impair performance through fatigue, chronotropic incompetence and side effects. Pulmonary vein isolation (PVI) may offer a more definitive therapeutic option but carries risks of atrial fibrosis, stiffening, and altered autonomic regulation, which may also influence exercise capacity. The investigators hypothesize that ablation will have a significant impact-either beneficial or detrimental-on the physical performance of athletes with AF. However, existing evidence is limited to small studies with inconsistent findings, underscoring the need for a dedicated study.

This prospective, multicentre interventional study will assess the effects of cardiac ablation in 100 endurance athletes with AF. Participants will undergo comprehensive pre- and post-ablation phenotyping, including electrocardiogram (ECG), cardiopulmonary exercise testing (CPET), echocardiography, Holter monitoring, and detailed training data collection (efficiency factor, acute and chronic training load). Clinical follow-up will extend to 12 months post-ablation.

The primary endpoint is the change in peak VO₂ (mL/kg/min) measured before ablation and after the procedure.

Secondary analyses will explore:

• Autonomic adaptations: including changes in maximum heart rate, heart rate recovery, heart rate reserve, and heart rate variability.
• Cardiac function: alterations in diastolic and atrial function assessed by echocardiography.
• Training and performance: objective measures such as efficiency factor, decoupling, functional threshold power, critical power, and acute and chronic training load.
• Technique comparison: differences in outcomes between pulsed field and radiofrequency ablation (e.g. atrial function, troponin release, …).
• Sex-specific effects: recognising the underrepresentation of women in sports cardiology research, the investigators will include female athletes according to incidence and evaluate potential differences in treatment response between sexes.
• Predictors of AF recurrence in endurance athletes