Clinical outcome in Japanese elderly patients with non-valvular atrial fibrillation taking warfarin: A single-center observational study

Background: Although a lower target prothrombin time-international normalized ratio (PT-INR) with warfarin therapy is recommended in Japan for atrial fibrillation (AF) patients ≥ 70 years of age, few studies have provided supporting data. The current study aimed to evaluate the clinical outcome in elderly Japanese patients with non-valvular AF who were taking warfarin. Methods: We conducted a cohort study of 845 consecutive non-valvular AF patients ≥ 70 years of age who were taking warfarin (median age, 74 years; 30.5% women) with a median follow-up period of 27 months (4-69 months). Of these patients, 29.7% had a history of stoke/transient ischemic attack (TIA), and 73.1% of the patients had a CHADS ₂ score ≥ 2. The occurrence of thromboembolic events, including ischemic stroke, TIA and other systemic embolisms, and major bleeding events were validated through a review of medical records. Results: The incidence of thromboembolic and major bleeding events were 3.8 and 2.1% per year, respectively. A higher incidence of both events was observed in patients with a CHADS ₂ score ≥ 3. The multivariate analysis showed that prior stroke/TIA (odds ratio 1.7, 95% CI 1.0-2.7) and diabetes (odds ratio 1.7, 95% CI 1.0-2.8) were independent risks of thromoembolic events. A HAS-BLED score ≥ 3 represented a risk for major bleeding (hazard ratio 2.8, 95% CI 1.7-4.6). A PT-INR of 1.5-2.5 indicated a low incidence of thromboembolic and major bleeding events in patients with a CHADS ₂ score ≥ 2. Conclusions: Our results demonstrate that a target PT-INR of 2.0 and a range of 1.5-2.5 may be safe for elderly Japanese patients with non-valvular AF.