title: Meta-analysis: antithrombotic therapy to prevent stroke in patients who have nonvalvular atrial fibrillation.
abstract: BACKGROUND
  Atrial fibrillation is a strong independent risk factor for stroke.
  
  
  OBJECTIVE
  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.
  
  
  METHODS
  Randomized trials identified by using the Cochrane Stroke Group search strategy, 1966 to March 2007, unrestricted by language.
  
  
  METHODS
  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.
  
  
  METHODS
  Two coauthors independently extracted information regarding interventions; participants; and occurrences of ischemic and hemorrhagic stroke, major extracranial bleeding, and death.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  Methodological features and quality varied substantially and often were incompletely reported.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Medicine (Neurology), University of Texas Health Science Center, San Antonio, Texas 78229-3900, USA. hartr@uthscsa.edu
authors.forename: Robert G
authors.initials: RG
authors.lastname: Hart
authors.forename: Lesly A
authors.initials: LA
authors.lastname: Pearce
authors.forename: Maria I
authors.initials: MI
authors.lastname: Aguilar
mesh_terms: D000368:Aged; D000925:Anticoagulants / Q000008:administration & dosage / Q000009:adverse effects; D001281:Atrial Fibrillation / Q000150:complications*; D005343:Fibrinolytic Agents / Q000009:adverse effects / Q000627:therapeutic use*; D006470:Hemorrhage / Q000139:chemically induced; D006801:Humans; D010975:Platelet Aggregation Inhibitors / Q000009:adverse effects / Q000627:therapeutic use; D020521:Stroke / Q000150:complications / Q000517:prevention & control*; D014859:Warfarin / Q000008:administration & dosage / Q000009:adverse effects
chemical_list: D000925:Anticoagulants; D005343:Fibrinolytic Agents; D010975:Platelet Aggregation Inhibitors; D014859:Warfarin