• Robert G Hart, Lesly A Pearce, and Maria I Aguilar.
• Department of Medicine (Neurology), University of Texas Health Science Center, San Antonio, Texas 78229-3900, USA. hartr@uthscsa.edu
• Ann. Intern. Med. 2007 Jun 19; 146 (12): 857867857-67.

BackgroundAtrial fibrillation is a strong independent risk factor for stroke.PurposeTo characterize the efficacy and safety of antithrombotic agents for stroke prevention in patients who have atrial fibrillation, adding 13 recent randomized trials to a previous meta-analysis.Data SourcesRandomized trials identified by using the Cochrane Stroke Group search strategy, 1966 to March 2007, unrestricted by language.Study SelectionAll published randomized trials with a mean follow-up of 3 months or longer that tested antithrombotic agents in patients who have nonvalvular atrial fibrillation.Data ExtractionTwo coauthors independently extracted information regarding interventions; participants; and occurrences of ischemic and hemorrhagic stroke, major extracranial bleeding, and death.Data SynthesisTwenty-nine trials included 28,044 participants (mean age, 71 years; mean follow-up, 1.5 years). Compared with the control, adjusted-dose warfarin (6 trials, 2900 participants) and antiplatelet agents (8 trials, 4876 participants) reduced stroke by 64% (95% CI, 49% to 74%) and 22% (CI, 6% to 35%), respectively. Adjusted-dose warfarin was substantially more efficacious than antiplatelet therapy (relative risk reduction, 39% [CI, 22% to 52%]) (12 trials, 12 963 participants). Other randomized comparisons were inconclusive. Absolute increases in major extracranial hemorrhage were small (< or =0.3% per year) on the basis of meta-analysis.LimitationMethodological features and quality varied substantially and often were incompletely reported.ConclusionsAdjusted-dose warfarin and antiplatelet agents reduce stroke by approximately 60% and by approximately 20%, respectively, in patients who have atrial fibrillation. Warfarin is substantially more efficacious (by approximately 40%) than antiplatelet therapy. Absolute increases in major extracranial hemorrhage associated with antithrombotic therapy in participants from the trials included in this meta-analysis were less than the absolute reductions in stroke. Judicious use of antithrombotic therapy importantly reduces stroke for most patients who have atrial fibrillation.

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