The primary objective of this trial is to assess the safety of an uninterrupted dabigatran etexilate periprocedural anticoagulant regimen compared to an uninterrupted warfarin regimen in Non-Valvular Atrial Fibrillation (NVAF) patients undergoing Atrial Fibrillation (AF) ablation in a PROBE (Prospective, randomized, open label, blinded end point) active controlled study.

Secondary objectives are to assess additional safety endpoints and efficacy in this clinical setting.

It is not intended to assess confirmatory hypothesis, this is an exploratory study.

Inclusion criteria:

• Male or female patients aged >= 18 years.
• Patients eligible for treatment with dabigatran etexilate 150 mg b.i.d. according to local label.
• Treatment naïve patients or patients on oral anticoagulant treatment with a Vitamin K Antagonist (VKA), dabigatran etexilate, rivaroxaban, apixaban or edoxaban.
• Patient with paroxysmal or persistent NVAF with a planned catheter ablation for AF unless it is performed an investigational ablation technique.
• AF must have been documented at least once either by ECG, Holter monitoring, loop recorder, telemetry, trans-telephonic monitoring, pacemaker or cardiac defibrillator read outs within 24 months prior to screening (Visit 1).
• The patient must be able to give informed consent in accordance with International Conference on Harmonisation (ICH) Good Clinical Practice (GCP) guidelines and local legislation and/or regulations.

Exclusion criteria:

• Patients with permanent AF.

• Patients with AF felt to be secondary to an obvious reversible cause such as, but not limited to, an acute myocardial infarction, pulmonary embolism, recent surgery, pericarditis or thyrotoxicosis.

• Patients with Left Atrium (LA) size >= 60 mm

• Patients with contraindications to systemic anticoagulation with heparin, warfarin or dabigatran etexilate

• Patients with a known allergy to warfarin tablets and it excipients or to dabigatran etexilate or its excipients

• Mechanical or biological heart valve prosthesis

• Severe renal impairment (estimated Creatinine Clearance (CrCl) calculated by Cockcroft-Gault equation) <30mL/min at screening

• Stroke within 1 month prior to screening visit

• Major surgery per investigator judgement within the previous month prior to screening.

• Patient has received an organ transplant or is on a waiting list for an organ transplant

• History of intracranial haemorrhage, intraocular, spinal, retroperitoneal or non-traumatic intra-articular bleeding

• Gastrointestinal haemorrhage within one month prior to screening, unless, in the opinion of the investigator, the cause has been permanently eliminated (e.g. by surgery).

• Major bleeding episode (ISTH definition) one month prior to the screening visit.

• Haemorrhagic disorder or bleeding diathesis (e.g. von Willebrand disease, haemophilia A or B or other hereditary bleeding disorder, history of spontaneous intra-articular bleeding, history of prolonged bleeding after surgery/intervention)

• Anaemia (haemoglobin <10g/dL) or thrombocytopenia including heparin-induced thrombocytopenia (platelet count <100 x 10^9/L) at screening

• Recent malignancy or radiation therapy (<=6 months prior to screening) unless, in the opinion of the Investigator, the estimated life expectancy is greater than 36 months

• Active liver disease as indicated by at least one of the following:

  -- Prior and persistent alanine aminotransferase or Aspartate transaminase or alkaline phosphatase >3x upper limit of normal and/or -- Known active hepatitis C and/or -- Known active hepatitis B and/or -- Known active hepatitis A

• Need for continued treatment with systemic ketoconazole, itraconazole, posaconazole, cyclosporine, tacrolimus, dronedarone, rifampicin, phenytoin, carbamazepine, St. John's Wort or any cytotoxic/myelosuppressive therapy.

• Pre-menopausal (last menstruation <=1 year prior to screening) who:

  • Are pregnant or breast-feeding or plan to become pregnant during study or
  • Are not surgically sterile or
  • Are of child bearing potential and not practising two acceptable method of birth control, or do not plan to continue practising an acceptable method of birth control throughout the trial

• Patients who have participated in another trial with an investigational drug or device within the past 30 days preceding the screening visit or are participating in another trial (patients participating in an observational study only will not be excluded)

• Patients not willing or able to comply with the protocol requirements or considered unreliable by the Investigator concerning the requirements for follow-up during the study and/or compliance with study drug administration, who have a life expectancy less than the expected duration of the trial due to concomitant disease and/or subjects who are institutionalised due to official or court orders and/or vulnerable subjects who are dependent on the Sponsor or the Investigator or the site, or patients who have any condition which in the opinion of the Investigator, would not allow safe participation in the study (e.g. drug addiction, alcohol abuse).