Study objective is to demonstrate that anticoagulation with the direct factor Xa inhibitor apixaban is not less safe than Vitamin-K-antagonists (VKA) therapy in patients undergoing catheter ablation of non-valvular AF in the prevention of peri-procedural complications.

The AXAFA trial will compare peri-ablational treatment with apixaban to peri-ablational treatment wit VKA in a randomized trial of patients undergoing catheter ablation of atrial fibrillation (AF).

AXAFA is an open-label trial designed to evaluate the safety and efficacy of two types of anticoagulant therapy, VKA therapy and therapy with the direct factor Xa inhibitor apixaban, in patients undergoing scheduled catheter ablation for AF. All patients will undergo the ablation procedure after pre-treatment with an anticoagulant (either apixaban in the "Xa group" or a vitamin K antagonist in the "VKA group").

Patients can undergo catheter ablation within the trial after at least 30 days of continuous effective anticoagulation. Ablation can be performed earlier when or timely after exclusion of atrial thrombi have been excluded by a clinically indicated by transthoracic echocardioggram (TEE). After TEE continuous effective anticoagulation must be ensured until the end of the trial.

In the MRI-substudy will be explored wether novel oral anticoagulants (NOAC) have the potential to reduce clinically silent brain lesions after catheter ablation of AF.

Inclusion Criteria:

I1. Non-valvular AF (ECG-documented) with a clinical indication for catheter ablation

I2. Clinical indication to undergo catheter ablation on continuous anticoagulant therapy

I3. Presence of at least one of the CHADS2 stroke risk factors

• Stroke or TIA
• age ≥ 75 years,
• hypertension, defined as chronic treatment for hypertension, estimated need for continuous antihypertensive therapy or resting blood pressure > 145/90 mm Hg,
• diabetes mellitus,
• symptomatic heart failure (NYHA ≥ II).

I4. Age ≥ 18 years

I5. Provision of signed informed consent

Exclusion Criteria:

General exclusion criteria

E1. Any disease that limits life expectancy to less than 1 year

E2. Participation in another clinical trial, either within the past two months or still ongoing

E3. Previous participation in AXAFA

E4. Pregnant women or women of childbearing potential not on adequate birth control: only women with a highly effective method of contraception (oral contraception or intra-uterine device) or sterile women can be randomised.

E5. Breastfeeding women

E6. Drug abuse or clinically manifest alcohol abuse

E7. Any stroke within 14 days before randomisation

E8. Coadministration with drugs that are strong dual inhibitors of cytochrome P450 3A4 (CYP3A4) and P-glycoprotein (P-gp) or strong dual inducers of CYP3A4 and P-gp (Appendix VIII).

Exclusion criteria related to a cardiac condition

E9. Valvular AF (as defined by the focussed update of the ESC guidelines on AF, i.e. severe mitral valve stenosis, mechanical heart valve). Furthermore, patients who underwent mitral valve repair are not eligible for AXAFA.

E10. Any previous ablation or surgical therapy for AF

E11. Cardiac ablation therapy for any indication (catheter-based or surgical) within 3 months prior to randomisation

E12. Clinical need for "triple therapy" (combination therapy of clopidogrel, acetylsalicylic acid, and oral anticoagulation)

E13. Other contraindications for use of VKA or apixaban

E14. Documented atrial thrombi less than 3 months prior to randomisation.

Exclusion criteria based on laboratory abnormalities

E15. Severe chronic kidney disease with an estimated glomerular filtration rate (GFR) < 15 ml/min