Optimal International Normalized Ratio for Warfarin Therapy in Elderly Korean Patients with Non-Valvular Atrial Fibrillation

Background and Objectives: Optimal international normalized ratio (INR) in elderly atrial fibrillation (AF) patients at higher risk of hemorrhagic events remains unclear. We investigated the efficacy and safety of low-intensity warfarin therapy (target international normalized ratio [INR], 1.6–2.6) in elderly Korean patients with nonvalvular AF (NVAF). Subjects and Methods: We enrolled 528 NVAF patients (mean age, 67±9 years; 361 men) who were actively taking warfarin. Major events were defined based on the annual rates of ischemic stroke, systemic embolism, and major bleeding events requiring blood transfusion or hospitalization. Time in therapeutic range (TTR) was 45±19% for all patients. Results: Ischemic stroke and systemic embolism occurred in 20 patients with INR between 1.00 and 2.44 (16 ischemic strokes and 4 systemic embolisms) and major bleeding in 37 patients with INR between 1.74 and no coagulation (exceed laboratory detection capability, more than 10 [7 intracranial hemorrhages, 21 gastrointestinal bleedings, and 9 others]). Incidence rates of ischemic or hemorrhagic events at INR<2.00, 2–3, and >3 were 3.0%, 1.4%, and 20.1% per year, respectively. In patients who were ≥70 years old, CHADS2, CHA2DS2VASc, and HAS-BLED scores were significantly higher compared with those in patients who were <70 years old. When we applied the INR between 1.6 and 2.6, as recommended by the Japanese AF Guideline for patients≥70 years old, the TTR increased from 43.8% to 58.6%. In addition, ischemic or hemorrhagic event rates decreased from 1.9% to 1.2% within the optimal INR range. Conclusion: Low-intensity warfarin therapy (INR, 1.6-2.6) should be considered in elderly Korean patients with NVAF.