title: Relationship of international normalized ratio to bleeding and thromboembolism rates in Taiwanese patients receiving vitamin K antagonist after mechanical valve replacement.
abstract: OBJECTIVE
  Asians may be less vulnerable to thrombotic disease than Caucasians. Optimum international normalized ratio (INR) anticoagulant therapy guidelines for Asian populations remain to be established. This study investigated the risk factors for major bleeding or thromboembolism (TE) in Taiwanese patients receiving mechanical aortic and/or mitral valve replacement, including INR < or > 2.0.
  
  
  METHODS
  The records of 563 Taiwanese patients receiving mechanical aortic and/or mitral valve replacement between 1996 and 2001 were retrospectively studied. Patient follow-up data was divided into several 6-month periods: 6-month increments after surgery if no bleeding or TE occurred and the 6 months preceding the adverse event when an event occurred. Data including warfarin sodium dosage and estimated INR unit for each time period were collected and analyzed.
  
  
  RESULTS
  A total of 3,391 records were retrieved for analysis with an average follow-up period of 3.3 +/- 1.4 years. The mean warfarin sodium dose was 2.86 +/- 1.09 mg/day and the INR was 1.86 +/- 0.66. Major bleeding events occurred in 20 patients (1.07% per patient-year) and TE events in 38 patients (2.04% per patient-year), accounting for a 3.11% rate of overall events (bleeding or TE) per patient-year. Multivariate risk analysis revealed follow-up age > 60 years and receiving mitral valve replacement were risk factors for overall events (odds ratio = 1.84, p = 0.021 for follow-up age > 60 years; odds ratio = 1.36, p = 0.019 for receiving mitral valve replacement), while gender, double valve replacement, valve type, INR < 2.0, and atrial fibrillation were not.
  
  
  CONCLUSIONS
  Our data suggest that low-intensity anticoagulant therapy (INR < 2.0) in Taiwanese patients was not associated with increased TE and bleeding rates compared to higher intensity anticoagulant therapy. Follow-up age over 60 years and valve replacement at the mitral site were associated with increased rate of overall events.
authors.affiliation: Department of Surgery, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan.
authors.forename: Hsi-Yu
authors.initials: HY
authors.lastname: Yu
authors.forename: Chih-Ho
authors.initials: CH
authors.lastname: Liu
authors.forename: Yih-Sharng
authors.initials: YS
authors.lastname: Chen
authors.forename: Shoei-Shen
authors.initials: SS
authors.lastname: Wang
authors.forename: Shu-Hsun
authors.initials: SH
authors.lastname: Chu
authors.forename: Fang-Yue
authors.initials: FY
authors.lastname: Lin
mesh_terms: D000925:Anticoagulants / Q000009:adverse effects / Q000627:therapeutic use*; D044466:Asian People; D005260:Female; D019918:Heart Valve Prosthesis Implantation / Q000009:adverse effects; D006470:Hemorrhage / Q000097:blood* / Q000139:chemically induced / Q000208:ethnology; D006801:Humans; D019934:International Normalized Ratio; D008297:Male; D008875:Middle Aged; D013923:Thromboembolism / Q000097:blood* / Q000208:ethnology / Q000517:prevention & control; D014812:Vitamin K / Q000037:antagonists & inhibitors*; D014859:Warfarin / Q000009:adverse effects / Q000627:therapeutic use*
chemical_list: D000925:Anticoagulants; D014812:Vitamin K; D014859:Warfarin