A trial fibrillation (AF) continues to be a leading cause of cerebrovascular morbidity and mortality resulting from cardioembolic stroke. When used appropriately, oral anticoagulation therapy has been shown to decrease the incidence of cardioembolic stroke in patients with AF by 50% to 60%.1 Appropriate use of warfarin anticoagulation requires precise adherence and monitoring to optimize the risk to benefit ratio associated with therapy and to ensure that therapy can be safely continued throughout the prescribed duration.