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Abstract
Atrial fibrillation is a strong independent risk factor for stroke.
To 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.
Randomized trials identified by using the Cochrane Stroke Group search strategy, 1966
to March 2007, unrestricted by language.
All published randomized trials with a mean follow-up of 3 months or longer that tested
antithrombotic agents in patients who have nonvalvular atrial fibrillation.
Two coauthors independently extracted information regarding interventions; participants;
and occurrences of ischemic and hemorrhagic stroke, major extracranial bleeding, and
death.
Twenty-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.
Methodological features and quality varied substantially and often were incompletely
reported.
Adjusted-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.