Heart Disease and Stroke

Evidence shows that warfarin is the drug of choice to prevent stroke in certain patients with atrial fibrillation

A common type of irregular heart beat, atrial fibrillation (AF), affects over 2 million people in the United States. Yet only one-third of AF patients, who are at risk of stroke, receive the anticoagulant warfarin to prevent stroke. Doctors may be underutilizing this drug, especially given the results of a recent study supported by the Agency for Healthcare Research and Quality (contract 290-97-0006). Scientific evidence gathered during the study suggests that physicians should prescribe warfarin to prevent a first stroke for patients with AF at average or greater risk of stroke. It also suggests that aspirin may prove useful in subgroups with a low risk of stroke, even though the evidence for this was inconclusive.

Doctors must trade off the benefits of anticoagulation that the drug warfarin provides to AF patients with its potential to cause hemorrhage due to blood thinning, notes Jodi B. Segal, M.D., M.P.H. Dr. Segal and colleagues at the Johns Hopkins University Evidence-based Practice Center recently conducted a meta-analysis of 11 trials of anticoagulants and antiplatelet agents to prevent stroke in adults with non-postoperative AF. Compared with patients taking placebo, those taking warfarin had a 70 percent less chance of a first stroke and a two-fold increased risk of minor hemorrhage. Thus, for AF patients at low risk of stroke, the benefit of warfarin may be offset by the increased risk of bleeding. Aspirin was inconclusively more efficacious than placebo for stroke prevention, and there was inconclusive evidence regarding more major bleeds. Assuming a baseline risk of a first stroke at 45 strokes per 1,000 patient-years, warfarin could prevent 30 strokes at the expense of only 6 additional major bleeds. Aspirin could prevent only 17 strokes but without increasing major hemorrhage. The studies that directly compared the two drugs suggested 25 percent fewer strokes among patients on warfarin than on aspirin, with only suggestive evidence for more major hemorrhage.

See "Prevention of thromboembolism in atrial fibrillation: A meta-analysis of trials of anticoagulants and antiplatelet drugs," by Jodi B. Segal, M.D., M.P.H., Robert L. McNamara, M.D., M.H.S., Marlene R. Miller, M.D., and others, in the January 2000 Journal of General Internal Medicine 15(1), pp. 56-67.

Editor's Note: The AHRQ-supported evidence report on which this journal article is based is being prepared for publication. We anticipate its release in late summer 2000. To add your name to the list to receive a copy of Evidence Report No. 12, Management of New Onset Atrial Fibrillation (AHRQ Publication No. 00-E007) when it is published, contact the AHRQ Publications Clearinghouse.

Return to Contents
Proceed to Next Article