Quality of Anticoagulation with Warfarin in Korean Patients with Atrial Fibrillation and Prior Stroke: A Multicenter Retrospective Observational Study

BACKGROUND AND PURPOSE: The quality of anticoagulation is critical for ensuring the benefit of warfarin, but this has been less well studied in Korean ischemic stroke patients with atrial fibrillation (AF). METHODS: This study retrospectively analyzed the data of patients who had an AF-related ischemic stroke and were treated with long-term warfarin therapy in 16 Korean centers. The quality of warfarin therapy was primarily assessed by the time in therapeutic range [TTR; international normalized ratio (INR), 2.0–3.0] and additionally by the proportion of INR values within the therapeutic range. RESULTS: The long-term warfarin-treated cohort comprised 1,230 patients. They were aged 70.1±9.7 years (mean±SD), 42.5% were female, and their CHA(2)DS(2)-VASc score was 4.75±1.41. The TTR analysis included 33,941 INR measurements for 27,487 months: per patients, 27.6 (SD, 22.4) INR measurements for 22.4 (SD, 12.9) months. The mean TTR of individual patients was 49.1% (95% confidence interval, 47.9–50.3%), and the TTR quartiles were <34.5, 34.5–49.1, 49.1–64.5%, and >64.5%. None of the 16 centers achieved a mean TTR of >60%. Of all INR measurements, 44.6% were within the therapeutic range, 41.7% were <2.0, and 13.7% were >3.0. CONCLUSIONS: In Korean ischemic stroke patients who had AF, the quality of warfarin therapy was low and might be inadequate to effectively prevent recurrent stroke or systemic embolism.