• O Benavente, R Hart, P Koudstaal, A Laupacis, and R McBride.
• Division of Neurology, Department of Medicine, University of Texas. Health Sciences Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, Texas 78284-7883, USA. benavente@uthscsa.edu
• Cochrane Db Syst Rev. 2000 Jan 1 (2): CD001925.

BackgroundAtrial fibrillation (AF) carries an increased risk of stroke; antiplatelet agents are proven effective for stroke prevention in other settings.ObjectivesThe objective of this review was to determine the efficacy and safety of antiplatelet therapy for prevention of stroke in patients with chronic non-valvular AF.Search StrategyWe searched the Cochrane Stroke Group Specialised Register of Trials, MEDLINE database (June 1999), and the database of the Antithrombotic Trialists Collaboration, as well as reference lists of relevant articles.Selection CriteriaAll randomized trials comparing antiplatelet therapies to placebo in patients with non-valvular AF and no history of transient ischemic attack (TIA) or stroke.Data Collection And AnalysisTrials for inclusion were independently selected by two reviewers who also extracted each outcome and double-checked the data. The Peto method was used for combining odds ratios. All analysis were, as far as possible, "intention-to-treat". Since the published results of two trials included 3-8% of participants with prior stroke or TIA, unpublished results excluding these participants were obtained from the Atrial Fibrillation Investigators.Main ResultsAmong 1680 participants without prior stroke/TIA, randomized to aspirin (N = 838) or placebo in two trials, aspirin was associated with nonsignificantly lower risks of ischemic stroke (OR = 0.71, CI 95% 0. 46 - 1.10), all stroke (OR = 0.70, CI 95% 0.45 - 1.08) all disabling/fatal stroke (OR =0.88, CI 95% 0.48 - 1.58) and the constellation of stroke, MI or vascular death (OR = 0.76, CI 95% 0. 54 - 1.05 ). Considering all randomized participants including those with prior stroke or TIA, reductions in these events by aspirin were consistently smaller and marginally statistically significant: ischemic stroke (OR = 0.77, CI 95% 0.60-1.00), all stroke (OR = 0.76, CI 95% 0.61 - 0.93), all disabling/fatal stroke (OR = 0.87, CI 95% 0.64 - 1.19) and the combined outcome (OR = 0.79, CI 95% 0.64 - 0. 99). No increase in major hemorrhage was seen, but the number of hemorrhagic events was small.Reviewer's ConclusionsConsidering all randomized data, aspirin modestly (by about 20%) reduces stroke and major vascular events in nonvalvular AF. For primary prevention among AF patients with an average stroke rate of 4.5%/year, about 10 strokes would be prevented yearly for every 1000 given aspirin.

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