title: Systematic review of observational studies assessing bleeding risk in patients with atrial fibrillation not using anticoagulants.
abstract: BACKGROUND
  Patients with atrial fibrillation considering use of anticoagulants must balance stroke reduction against bleeding risk. Knowledge of bleeding risk without the use of anticoagulants may help inform this decision.
  
  
  OBJECTIVE
  To determine the rate of major bleeding reported in observational studies of atrial fibrillation patients not receiving Vitamin K antagonists (VKA).
  
  
  METHODS
  We searched MEDLINE, EMBASE and CINAHL to October 2011 and examined reference lists of eligible studies and related reviews.
  
  
  METHODS
  All longitudinal cohort studies that included over 100 adult patients with atrial fibrillation not receiving VKA.
  
  
  METHODS
  Teams of two reviewers independently and in duplicate adjudicated eligibility, assessed risk of bias and abstracted study characteristics and outcomes.
  
  
  RESULTS
  Twenty-one eligible studies included 96,448 patients. Major bleeding rates varied widely, from 0 to 4.69 events per 100 patient-years. The pooled estimate in 13 studies with 78839 patients was 1.59 with a 99% confidence interval of 1.10 to 2.3 and median 1.42 (interquartile range 0.62-2.70). Pooled estimates for fatal bleeding and non-fatal bleeding from 4 studies that reported these outcomes were, respectively, 0.40 (0.34 to 0.46) and 1.18 (0.30 to 4.56) per 100 patient-years. In 9 randomized controlled trials (RCTs) the median rate of major bleeding in patients not receiving either anticoagulant or antiplatelet therapy was 0.6 (interquartile 0.2 to 0.90), and in 12 RCTs the median rate of major bleeding in patients receiving a single antiplatelet agent was 0.75 (interquartile 0.4 to 1.4).
  
  
  CONCLUSIONS
  Results suggest that patients with atrial fibrillation not receiving VKA enrolled in observational studies represent a population on average at higher risk of bleeding.
authors: Pharmaceutical Sciences Postgraduate Course, University of Sorocaba, Sao Paulo, Brazil.
authors: Luciane Cruz
authors: LC
authors: Lopes
authors: Department of Medicine, Division of Cardiology, McMaster University, Hamilton, Ontario, Canada.
authors: Frederick A
authors: FA
authors: Spencer
authors: Internal Medicine Department, School of Medicine, Pontificia Universidad Catolica de Chile, Santiago, Chile ; Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Ontario, Canada.
authors: Ignacio
authors: I
authors: Neumann
authors: Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Ontario, Canada.
authors: Matthew
authors: M
authors: Ventresca
authors: Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Ontario, Canada ; Department of Anesthesia, McMaster University, Hamilton, Ontario, Canada ; Stanford Prevention Research Center, Stanford University, Stanford, California, United States of America.
authors: Shanil
authors: S
authors: Ebrahim
authors: Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Ontario, Canada.
authors: Qi
authors: Q
authors: Zhou
authors: Health Sciences Library McMaster University, Hamilton, Ontario, Canada.
authors: Neera
authors: N
authors: Bhatnagar
authors: Department of Medicine, McMaster University, Hamilton, Ontario, Canada ; Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Ontario, Canada.
authors: Sam
authors: S
authors: Schulman
authors: Department of Medicine, Division of Hematology and Thromboembolism, McMaster University, Hamilton, Ontario, Canada.
authors: John
authors: J
authors: Eikelboom
authors: Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Ontario, Canada.
authors: Gordon
authors: G
authors: Guyatt
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000925:Anticoagulants / Q000627:therapeutic use*; D001281:Atrial Fibrillation / Q000097:blood* / Q000150:complications / Q000188:drug therapy*; D005260:Female; D006470:Hemorrhage / Q000175:diagnosis*; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D064887:Observational Studies as Topic; D016032:Randomized Controlled Trials as Topic; D012306:Risk; D014812:Vitamin K / Q000037:antagonists & inhibitors
chemical_list: D000925:Anticoagulants; D014812:Vitamin K