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.