title: Accumulation of risk factors increases risk of thromboembolic events in patients with nonvalvular atrial fibrillation.
abstract: BACKGROUND
  Accumulation of risk factors could increase thromboembolic event rates in patients with nonvalvular atrial fibrillation (NVAF). To validate this hypothesis, a post hoc analysis was performed to determine the relationship of risk levels and thromboembolic events in patients with NVAF from our previous prospective study.
  
  
  RESULTS
  Risk levels were quantified using the CHADS2 index in 509 patients with NVAF (66.3+/-10.3 years old). One point each was given for patients with advanced age (>or=75 years), hypertension, congestive heart failure, and diabetes mellitus, and 2 points, to those with prior ischemic stroke or transient ischemic attack. Patients with a CHADS2 score of 0 were classified as low risk, 1 to 2 a moderate risk and 3 or more were high risk. Because hypertrophic cardiomyopathy had emerged as an independent risk factor for thromboembolism, the original CHADS2 score was modified by adding 1 point to patients with hypertrophic cardiomyopathy. Warfarin was given to 263 patients (mean international normalized ratio (INR) at enrollment, 1.86), antiplatelets (aspirin or ticlopidine) to 163 patients and no antithrombotic therapy to 83. During a mean follow-up period of 2 years, 31 thromboembolic events occurred. As the risk level (modified CHADS2 score) increased, the event rate increased for both the patient groups receiving warfarin (p=0.035) and those not receiving warfarin (p=0.048). When a thromboembolic event occurred in patients who had been treated with warfarin, the mean INR level was 1.41. Twelve (75%) of 16 patients complicated with thromboembolism during warfarin treatment had INR levels below the optimal levels (1.6-2.6) for Japanese patients.
  
  
  CONCLUSIONS
  Accumulation of risk factors could increase risk of thromboembolic events in patients with NVAF. Adherence to the guidelines for anticoagulation therapy is recommended.
authors.affiliation: Second Department of Internal Medicine, University of Toyama, Toyama, Japan. hiroshi@med.u-toyama.ac.jp
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Inoue
authors.forename: Takashi
authors.initials: T
authors.lastname: Nozawa
authors.forename: Tadakazu
authors.initials: T
authors.lastname: Hirai
authors.forename: Atsushi
authors.initials: A
authors.lastname: Iwasa
authors.forename: Ken
authors.initials: K
authors.lastname: Okumura
authors.forename: Jong-Dae
authors.initials: JD
authors.lastname: Lee
authors.forename: Akihiko
authors.initials: A
authors.lastname: Shimizu
authors.forename: Motonobu
authors.initials: M
authors.lastname: Hayano
authors.forename: Katsusuke
authors.initials: K
authors.lastname: Yano
mesh_terms: D000368:Aged; D000925:Anticoagulants / Q000008:administration & dosage; D001281:Atrial Fibrillation / Q000150:complications / Q000453:epidemiology*; D009202:Cardiomyopathies / Q000150:complications / Q000453:epidemiology*; D005260:Female; D006801:Humans; D019934:International Normalized Ratio; D007564:Japan; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012307:Risk Factors; D013923:Thromboembolism / Q000188:drug therapy / Q000453:epidemiology* / Q000209:etiology
chemical_list: D000925:Anticoagulants