How Well Does the Target INR Level Maintain in Warfarin- Treated Patients with Non-ValvularAtrial Fibrillation?

Purpose: Although warfarin is an effective oral anticoagu-lation (OAC) drug to reduce the risk of thromboembolism in patients with non-valvular atrial fibrillation (NVAF), long term follow-up data are scarce to be certain whether the target INR level is maintained in warfarin-treated patients in Korea. The aim of this study was to evaluate how well INRs are maintained within the target range using a new index, INR stability ( = 100 × number of INRs within target range/ total number of INR measurements) which we made, and to find out any correlation between thromboembolic events and INR stability. Materials and Methods: This study was an observational analysis of retrospectively collected data of 129 patients with NVAF from April 2000 to December 2005 at a single tertiary hospital. All patients were registered at the anticoagulation service. Results: The median duration o