Warfarin anticoagulation intensity in Japanese nonvalvular atrial fibrillation patients: a J-RHYTHM Registry analysis.

BACKGROUND To maximize protection against stroke with minimal bleeding, warfarin therapy in nonvalvular atrial fibrillation (NVAF) requires tight control within a narrow therapeutic range, which might depend on racial variations. METHODS The J-RHYTHM Registry followed 6404 NVAF patients treated with warfarin for 2 years. Using international normalized ratios (INRs) at or closest to the embolic and intracranial hemorrhagic (ICH) events, we determined odds ratios for ischemic stroke/systemic embolism (SE) and ICH according to any given INR with a reference INR range including 2.0. RESULTS Ischemic stroke and SE occurred in 97 of the patients and ICH occurred in 49. The estimated INR-risk relationships showed characteristics of Japanese NVAF patients. Compared to INR-risk relationships reported for Westerners, those observed in Japanese patients were virtually identical for ischemic stroke/SE and shifted leftward by approximately 0.5 INR for ICH. CONCLUSION This is the largest Japanese study providing fundamental data necessary to establish optimal anticoagulation intensities. Japanese NVAF patients may require narrower therapeutic ranges than Westerners.