A Cochrane review [Abstract] 1 included 3 studies with a total of 1 965 subjects with atrial firillation (AF) with no prior stroke or TIA. The studies compared aspirin in dosages ranging from 75 mg to 325 mg per day and 125 mg every other day to placebo (in 2 studies) or control (in 1 study). The mean duration of follow up was 1.3 years. Aspirin was associated with nonsignificantly lower risk of ischaemic stroke (OR 0.70, 95% CI 0.46 to 1.07), all stroke (OR 0.70, 95% CI 0.47 to 1.07), all disabling or fatal stroke (OR 0.86, 95% CI 0.50 to 1.49) and all-cause death (OR 0.75, 95% CI 0.54 to 1.04). The combination of stroke, myocardial infarction or vascular death was significantly reduced (OR 0.71, 95% CI 0.51 to 0.97 ). No increase in intracranial hemorrhage or major extracranial hemorrhage was observed.
A meta-analysis 2 included 16 studies with a total of 9 874 subjects (mean follow-up 1.7 years) in order to characterize the efficacy and safety of anticoagulants and antiplatelet agents for prevention of stroke in patients with atrial fibrillation. Aspirin (6 studies, n=3 119) reduced stroke by 22% (95% CI 2% to 38%). Adjusted-dose warfarin (6 studies, n=2 900) reduced stroke by 62% (95% CI 48% to 72%). Adjusted-dose warfarin (5 studies, n=2 837) was more efficacious than aspirin (RRR 36%, CI 14% to 52%).
A double-blind study 3 randomized 5 599 subjects with AF who were at increased risk for stroke and for whom vitamin K antagonist therapy was unsuitable to receive apixaban 5 mg twice daily or aspirin (81 to 324 mg per day). The mean follow up period was 1.1 years. The data and safety monitoring board recommended early termination of the study because of a clear benefit in favor of apixaban. Stroke or systemic embolism occurred 1.6% per year in the apixaban group and 3.7% per year in the aspirin group (HR 0.45, 95% CI 0.32 to 0.62). Major bleeding occurred 1.4% per year in the apixaban group and 1.2% per year in the aspirin group (HR 1.13, 95% CI 0.74 to 1.75).
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