Inclusion Criteria- Nonvalvular AF (NVAF) verified by at least two ECGs in the last year separated by at least one week.
- Previous cerebral ischemic attack (stroke or TIA, >30 days prior to randomization)
- Previous systemic embolism.
- Symptomatic congestive heart failure (CHF)
- Impaired left ventricular systolic function
- Diabetes mellitus
- Hypertension requiring anti-hypertensive treatment.
Exclusion Criteria- AF secondary to reversible disorders, eg hyperthyroidism, drugs and pulmonary embolism
- Known contraindication to VKA treatment
- Presence of a valvular heart disease, mechanical heart valves, active endocarditis, left ventricular aneurysm or thrombus, atrial myxoma or any condition other than AF requiring chronic anticoagulation treatment
- Conditions associated with increased risk of major bleeding for example: history of intracranial bleeding, history of bleeding gastrointestinal disorder or major surgical procedure or trauma two weeks prior to randomization