title: Implications of stroke risk criteria on the anticoagulation decision in nonvalvular atrial fibrillation: the Anticoagulation and Risk Factors in Atrial Fibrillation (ATRIA) study.
abstract: BACKGROUND
  Warfarin dramatically reduces the risk of stroke in patients with nonvalvular atrial fibrillation (NVAF) but increases the likelihood of bleeding. Accurately identifying patients who need anticoagulation is critical. We assessed the potential impact of prominent stroke risk classification schemes on this decision in a large sample of patients with NVAF.
  
  
  RESULTS
  We used clinical and electrocardiographic databases to identify 13 559 ambulatory patients with NVAF from July 1996 through December 1997. We compared the proportion of patients classified as having a low enough stroke risk to receive aspirin using published criteria from the Atrial Fibrillation Investigators (AFI), American College of Chest Physicians (ACCP), and the Stroke Prevention in Atrial Fibrillation Investigators (SPAF). In this cohort, AFI criteria classified 11% as having a low stroke risk, compared with 23% for ACCP and 29% for SPAF (kappa range, 0.44 to 0.85). This 2- to-3-fold increase in low stroke risk patients by ACCP and SPAF criteria primarily resulted from the inclusion of many older subjects (65 to 75 years+/-men >75 years) with no additional clinical stroke risk factors.
  
  
  CONCLUSIONS
  The age threshold for assigning an increased stroke risk has a dramatic impact on whether to recommend warfarin in populations of patients with NVAF. Large, prospective studies with many stroke events are needed to precisely determine the relationship of age to stroke risk in AF and to identify which AF subgroups are at a sufficiently low stroke risk to forego anticoagulation.
authors.affiliation: Division of Research, Kaiser Permanente Medical Care Program, Oakland, CA 94611, USA. axg@dor.kaiser.org
authors.forename: A S
authors.initials: AS
authors.lastname: Go
authors.forename: E M
authors.initials: EM
authors.lastname: Hylek
authors.forename: K A
authors.initials: KA
authors.lastname: Phillips
authors.forename: L H
authors.initials: LH
authors.lastname: Borowsky
authors.forename: L E
authors.initials: LE
authors.lastname: Henault
authors.forename: Y
authors.initials: Y
authors.lastname: Chang
authors.forename: J V
authors.initials: JV
authors.lastname: Selby
authors.forename: D E
authors.initials: DE
authors.lastname: Singer
mesh_terms: D000368:Aged; D000925:Anticoagulants / Q000627:therapeutic use*; D001241:Aspirin / Q000627:therapeutic use; D001281:Atrial Fibrillation / Q000188:drug therapy*; D015331:Cohort Studies; D005343:Fibrinolytic Agents / Q000627:therapeutic use; D006351:Heart Valves; D006801:Humans; D012307:Risk Factors; D020521:Stroke / Q000453:epidemiology*; D014859:Warfarin / Q000627:therapeutic use*
chemical_list: D000925:Anticoagulants; D005343:Fibrinolytic Agents; D014859:Warfarin; D001241:Aspirin