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Reviews: Robert G. Hart, Lesly A. Pearce, and Maria I. Aguilar Meta-analysis: Antithrombotic Therapy to Prevent Stroke in Patients Who Have Nonvalvular Atrial Fibrillation Ann Intern Med 2007; 146: 857-867 [Abstract] [Full text] [PDF]

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Adjusted-dose warfarin vs. aspirin for prevention of stroke in patients with atrial fibrillation

Robert G. Hart   (27 August 2007)

Adjusted-dose warfarin vs. aspirin for prevention of stroke in patients with atrial fibrillation 27 August 2007
Robert G. Hart, MD University of Texas Health Science Center Send rapid response to journal: Re: Adjusted-dose warfarin vs. aspirin for prevention of stroke in patients with atrial fibrillation HARTR{at}uthscsa.edu Robert G. Hart	To The Editor: The recently published randomized Birmingham Atrial Fibrillation Trial of the Aged (BAFTA) compared adjusted-dose warfarin (target INR 2-3) with aspirin (75 mg per day) in 973 atrial fibrillation patients age >75 years (mean = 81.5 years) managed by U.K. general practitioners (1). The important results indicate that the relative efficacy and safety of warfarin for stroke prevention can be extended to very elderly patients managed by non-specialists. Since BAFTA appears likely to be the last large trial comparing adjusted-dose warfarin with aspirin (and addition of BAFTA results increases the total number of stroke events available for meta-analysis by 42%), here we add the BAFTA results to our updated meta- analysis of antithrombotic trials in patients who have atrial fibrillation (2). Including BAFTA, nine randomized trials enrolling 4620 participants compared adjusted-dose warfarin with aspirin. By meta-analysis, the relative risk reduction by warfarin over aspirin is 39% (CI 19 to 53) in these eight predominantly primary prevention trials and single secondary prevention trial and remained at 39% when three comparisons of warfarin with non-aspirin antiplatelet agents were included (1). The meta-analytic estimate for the absolute risk reduction by warfarin over aspirin for primary prevention is about 1% per year (Table). Based on all available randomized data, the relative risk reduction in all strokes by adjusted-dose warfarin vs. antiplatelet therapy is about 40%. Despite some inconsistencies in results of earlier, smaller trials (Figure will appear in print), this number appears to be stable and is the best available estimate. Study N Strokes / Patients / Patient-Years Relative Risk Reduction (95% CI) Absolute Risk Reduction for Primary Prevention (%/yr)# Adjusted-dose warfarin vs. aspirin 8 previous trials (2) 3647 91/1803/3740 vs. 142/1844/3730 38% (18 to 52) 0.7% per yr BAFTA ^(1) 973 35/488/1333 vs. 62/485/1263 47% (19 to 66) 2.3% per yr 9 aspirin trials+ 4620 126/2291/5073 vs. 204/2329/4993 39% (19 to 53) 0.9% per yr Adjusted-dose warfarin vs. aspirin or non-aspirin antiplatelet agents 12 antiplatelet trials+ 12721 215/6353/10279 vs. 344/6368/10209 39% (27 to 49) 1.0% per yr Robert G. Hart, M.D. Lesly A. Pearce, M.S. Maria I. Aguilar, M.D. References: 1. Mant J, Hobbs FD, Fletcher K, Roalfe A, Fitzmaurice D, Lip GYH et al. on behalf of the BAFTA investigators and the Midland Research Practices Network. Warfarin versus aspirin for stroke prevention in an elderly community population with atrial fibrillation (the Birmingham Atrial Fibrillation Treatment of the Aged Study, BAFTA): a randomised controlled trial. Lancet 2007; 370: 493-503. 2. Hart RG, Pearce LA, Aguilar MI. Meta-analysis: Antithrombotic therapy to prevent stroke in patients who have nonvalvular atrial fibrillation. Ann Intern Med 2007: 146: 857-67. Conflict of Interest: None declared