Determinants of Warfarin Use and International Normalized Ratio Levels in Atrial Fibrillation Patients in Japan: Subanalysis of the J-RHYTHM Registry

Background: Determinants of warfarin use and anticoagulation levels in atrial fibrillation (AF) patients have not been clarified thoroughly. Methods and Results: A total of 6,324 patients with non-valvular AF and congestive heart failure, hypertension, age, diabetes, prior stroke (CHADS2) score ≥1 were used to investigate determinants of warfarin use, and 6,932 patients with AF receiving warfarin were used to investigate determinants of international normalized ratio (INR) of prothrombin time. Target INR levels for non-valvular AF patients were 1.6-2.6 for patients aged ≥70 years and 2-3 for patients aged