Secondary Prevention of Stroke with Warfarin in Patients with Nonvalvular Atrial Fibrillation: Subanalysis of the J-RHYTHM Registry.

Background: Prior ischemic stroke or transient ischemic attack (TIA) is a high risk for thromboembolism in patients with nonvalvular atrial fibrillation (NVAF). To clarify rates of thromboembolic and hemorrhagic events, and target intensities of warfarin for secondary prevention, a subanalysis was performed using data from the J-RHYTHM Registry.

Methods: Of 7937 outpatients with atrial fibrillation, 7406 with NVAF (men 70.8%, 69.8 ± 10.0 years) were followed for 2 years or until an event occurred. Event rates and effect of warfarin were compared between patients with (secondary prevention) and without (primary prevention) prior stroke/TIA.

Results: Prevalence of male sex, diabetes mellitus, and mean age were higher in the secondary prevention group, showing a higher CHADS2 (congestive heart failure, hypertension, age 75 years or older, diabetes mellitus, and history of stroke or TIA) score than the primary prevention group (3.5 ± 1.0 versus 1.4 ± 1.0, P < .001). In the secondary prevention group, 93.4% of patients received warfarin and their time in therapeutic range was 62.8%. During follow-up, thromboembolism occurred more frequently in the secondary than in the primary prevention group (2.8% versus 1.5%, P = .004), especially in patients without warfarin. Major hemorrhage also occurred more frequently in the secondary prevention group (3.0% versus 1.7%, P = .006). Compared with patients not taking warfarin, combined rates of both events were lower at an international normalized ratio (INR) of 1.6-2.59 in patients taking warfarin in the secondary as well as in the primary prevention groups.

Conclusions: Both thromboembolism and major hemorrhage occurred more frequently in NVAF patients with prior ischemic stroke/TIA. Target INR should be 1.6-2.59 for secondary as well as primary prevention of thromboembolism in Japanese NVAF patients.