• Jun Hyung Kim, Young Bin Song, Dae Hee Shin, Je Sang Kim, Jin-Oh Choi, Young Kun On, and June Soo Kim.
• Division of Cardiology, Department of Medicine, Cardiac and Vascular Center, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
• Yonsei Med. J. 2009 Feb 28; 50 (1): 83-8.

PurposeAlthough warfarin is an effective oral anticoagulation (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 x 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 MethodsThis 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.ResultsThe median duration of follow up was 2.03 years (interquartile range 1.35 - 2.96). During the follow-up period, 60.9 +/- 14.9% of the INR were within the target INR range. INR stability was not significantly different between patients without and with stroke (61.2 +/- 15.0% vs 53.3 +/- 4.9%). Among the known factors affecting fluctuations of the INR value, the most frequent factor was noncompliance (41.8%).ConclusionThe present study showed that it was not enough to maintain INR values within the target range in warfarin-treated patients with NVAF even at a tertiary hospital. Noncompliance is an important problem which interferes with maintaining target INR range.

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