Renal Dysfunction Affects Anticoagulation Control With Warfarin and Outcomes in Japanese Elderly Patients With Non-Valvular Atrial Fibrillation

BACKGROUND: It is unclear whether renal dysfunction affects warfarin control in patients with non-valvular atrial fibrillation (NVAF). METHODS AND RESULTS: Using a dataset from the J-RHYTHM Registry, time in therapeutic range (TTR) of the international normalized ratio (INR) of prothrombin time, and creatinine clearance (CrCl) were determined in elderly patients aged ≥70 years. Target INR values were 1.6-2.6 following Japanese guidelines. Incidences of thromboembolism, major hemorrhage, and all-cause death were determined over 2 years. Of 7,406 NVAF patients enrolled in the registry, 2,782 elderly patients (mean age, 75 years) had data for CrCl measured at baseline and TTR. TTR values were lower in the lower CrCl groups (P<0.001 for trend). CrCl <30 mL/min was independently associated with TTR <65% (odds ratio, 1.49; 95% confidence interval, 1.13-1.95; P=0.004). In the multivariate analysis, TTR <65% was independently associated with thromboembolism (hazard ratio, 2.26; 95% confidence interval, 1.37-3.72; P=0.001), but CrCl was not (CrCl <30 mL/min, 1.68, 0.41-6.85, P=0.473). However, CrCl <30 mL/min and TTR <65% were independently associated with all-cause death (5.32, 1.56-18.18, P=0.008 and 1.60, 1.07-2.38, P=0.022, respectively) and the composite event (thromboembolism, major hemorrhage and all-cause death) (2.03, 1.10-3.76, P=0.024 and 1.58, 1.22-2.04, P=0.001, respectively). CONCLUSIONS: Elderly NVAF patients with renal dysfunction had poor warfarin control, which was associated with higher risk of thromboembolism and all-cause death.