8. Patients with risk factors of stroke may be enrolled in the study, provided that the disease process has been stable or controlled on medication for greater than 3 months prior to Screening. Patients receiving anticoagulation with warfarin are eligible for inclusion in the study if the International Normalized Ratio (INR) for prothrombin time is within the therapeutic range for prophylaxis (1.4-3.0) and the dose of warfarin is stable.