Key result
Warfarin with a target INR of 1.6-2.6 in Japanese patients with NVAF was associated with lower thromboembolic events compared to no warfarin (1.3-1.5% vs 3.0%; P=0.0059).
Why the study?
Does warfarin at specific target INR levels prevent thromboembolic events without excessive hemorrhage in Japanese patients with non-valvular atrial fibrillation?
Cohort (n=7,527)
Does warfarin at specific target INR levels prevent thromboembolic events without excessive hemorrhage in Japanese patients with non-valvular atrial fibrillation?
In Japanese patients with non-valvular atrial fibrillation, an INR of 1.6-2.6 is safe and effective for preventing thromboembolic events, while higher INRs increase the risk of major hemorrhage.
Answers are grounded in this paper and cite their sources.
May support lower INR targets in Japanese NVAF; hypothesis-generating and requires randomized confirmation before practice change.
BACKGROUND: Target anticoagulation levels for warfarin in Japanese patients with non-valvular atrial fibrillation (NVAF) are unclear. METHODS AND RESULTS: Of 7,527 patients with NVAF, 1,002 did not receive warfarin (non-warfarin group), and the remaining patients receiving warfarin were divided into 5 groups based on their baseline international normalized ratio (INR) of prothrombin time (≤1.59, 1.6-1.99, 2.0-2.59, 2.6-2.99, and ≥3.0). Patients were followed-up prospectively for 2 years. Primary endpoints were thromboembolic events (cerebral infarction, transient ischemic attack, and systemic embolism), and major hemorrhage requiring hospital admission. During the follow-up period, thromboembolic events occurred in 3.0% of non-warfarin group, but at lower frequencies in the warfarin groups (2.0, 1.3, 1.5, 0.6, and 1.8%/2 years for INR values of ≤1.59, 1.6-1.99, 2.0-2.59, 2.6-2.99, and ≥3.0, respectively; P=0.0059). Major hemorrhage occurred more frequently in warfarin groups (1.5, 1.8, 2.4, 3.3, and 4.1% for INR values ≤1.59, 1.6-1.99, 2.0-2.59, 2.6-2.99, and ≥3.0, respectively; P=0.0041) than in non-warfarin group (0.8%/2 years). These trends were maintained when the analyses were confined to patients aged ≥70 years. CONCLUSIONS: An INR of 1.6-2.6 is safe and effective at preventing thromboembolic events in patients with NVAF, particularly patients aged ≥70 years. An INR of 2.6-2.99 is also effective, but associated with a slightly increased risk in major hemorrhage. (UMIN Clinical Trials Registry UMIN000001569)
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Inoue et al. (2013) conducted a cohort in Non-valvular atrial fibrillation (NVAF) (n=7,527). Warfarin vs. No warfarin was evaluated on Thromboembolic events (cerebral infarction, transient ischemic attack, and systemic embolism), and major hemorrhage requiring hospital admission (p=0.0059). Warfarin with a target INR of 1.6-2.6 in Japanese patients with NVAF was associated with lower thromboembolic events compared to no warfarin (1.3-1.5% vs 3.0%; P=0.0059).
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