title: Stability of High-Quality Warfarin Anticoagulation in a Community-Based Atrial Fibrillation Cohort: The Anticoagulation and Risk Factors in Atrial Fibrillation (ATRIA) Study.
abstract: Warfarin reduces ischemic stroke risk in atrial fibrillation (AF) but increases bleeding risk. Novel anticoagulants challenge warfarin as stroke-preventive therapy for AF. They are available at fixed doses but are more costly. Warfarin anticoagulation at a time in therapeutic range (TTR) ≥70% is similarly as effective and safe as novel anticoagulants. It is unclear whether AF patients with TTR ≥70% will remain stably anticoagulated and avoid the need to switch to a novel anticoagulant. We assessed stability of warfarin anticoagulation in AF patients with an initial TTR ≥70%.
  
  
  
  Within the community-based Anticoagulation and Risk Factors in AF (ATRIA) cohort followed from 1996 to 2003, we identified 2841 new warfarin users who continued warfarin over 9 months. We excluded months 1 to 3 to achieve a stable dose. For the 987 patients with TTR ≥70% in an initial 6-month period (TTR1; months 4-9), we described the distribution of TTR2 (months 10-15) and assessed multivariable correlates of persistent TTR ≥70%. Of patients with TTR1 ≥70%, 57% persisted with TTR2 ≥70% and 16% deteriorated to TTR2 <50%. Only initial TTR1 ≥90% (adjusted odds ratio 1.47, 95% CI 1.07-2.01) independently predicted TTR2 ≥70%. Heart failure was moderately associated with marked deterioration (TTR2 <50%); adjusted odds ratio 1.45, 95% CI 1.00-2.10.
  
  
  
  Nearly 60% of AF patients with high-quality TTR1 on warfarin maintained TTR ≥70% over the next 6 months. A minority deteriorated to very poor TTR. Patient features did not strongly predict TTR in the second 6-month period. Our analyses support watchful waiting for AF patients with initial high-quality warfarin anticoagulation before considering alternative anticoagulants.
authors.affiliation: Harvard Medical School, Boston, MA.
authors.forename: Liane O
authors.initials: LO
authors.lastname: Dallalzadeh
authors.affiliation: Division of Research, Kaiser Permanente of Northern California, Oakland, CA Department of Medicine, Epidemiology and Biostatistics, University of California, San Francisco, CA Department of Health Research and Policy, Stanford University School of Medicine, Stanford, CA.
authors.forename: Alan S
authors.initials: AS
authors.lastname: Go
authors.affiliation: Harvard Medical School, Boston, MA Division of General Internal Medicine, Massachusetts General Hospital, Boston, MA.
authors.forename: Yuchiao
authors.initials: Y
authors.lastname: Chang
authors.affiliation: Division of General Internal Medicine, Massachusetts General Hospital, Boston, MA.
authors.forename: Leila H
authors.initials: LH
authors.lastname: Borowsky
authors.affiliation: Division of Hospital Medicine, University of California, San Francisco, CA.
authors.forename: Margaret C
authors.initials: MC
authors.lastname: Fang
authors.affiliation: Harvard Medical School, Boston, MA Division of General Internal Medicine, Massachusetts General Hospital, Boston, MA desinger@mgh.harvard.edu.
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Singer
mesh_terms: D000368:Aged; D001281:Atrial Fibrillation / Q000150:complications / Q000188:drug therapy* / Q000453:epidemiology; D015331:Cohort Studies; D015897:Comorbidity; D003435:Crotalid Venoms / Q000627:therapeutic use*; D005260:Female; D006333:Heart Failure / Q000453:epidemiology; D006801:Humans; D016015:Logistic Models; D008297:Male; D015999:Multivariate Analysis; D016017:Odds Ratio; D020521:Stroke / Q000209:etiology / Q000517:prevention & control*; D014859:Warfarin / Q000627:therapeutic use*
chemical_list: D003435:Crotalid Venoms; C465285:anticoagulation factor I, Agkistrodon acutus; D014859:Warfarin
keywords: anticoagulants; arrhythmia; embolism; prevention; risk factors