Inclusion Criteria- Patients with non valvular atrial fibrillation and any of the following:
- = 60 years old with no heart disease.
- 60 years old with heart disease but no risk factors.
- >/=60 years old and =75 years old with no risk factors and no heart disease.
- Must be able to take aspirin.
Exclusion Criteria- Previous heart attack or stroke.
- History of high blood pressure, diabetes or a prior blood clot.
- Liver or kidney disease.
- Need for anti-thrombotic or anti-platelet drugs.
- Need for cardiovascular medicines.