Key result
Poor INR control in patients with atrial fibrillation taking warfarin was associated with higher rates of stroke or systemic embolism compared to good control (2.10% vs 1.07%, P=.02).
Why the study?
Does the level of INR control affect the rates of death, bleeding, MI, and stroke or SEE in patients with atrial fibrillation taking warfarin?
RCT (n=3,587)
Does the level of INR control affect the rates of death, bleeding, MI, and stroke or SEE in patients with atrial fibrillation taking warfarin?
Absolute Event Rate: 2.1% vs 1.07%
p-value: p=.02
In patients with atrial fibrillation taking warfarin, poor INR control is associated with significantly higher risks of mortality, major bleeding, MI, and stroke compared to good control.
Supports closer INR monitoring in warfarin-treated AF; leaves open whether targeted interventions reduce events.
Background: Warfarin sodium reduces stroke risk in patients with atrial fibrillation, but international normalized ratio (INR) monitoring is required. Target INRs are frequently not achieved, and the risk of death, bleeding, myocardial infarction (MI), and stroke or systemic embolism event (SEE) may be related to INR control. Methods: We analyzed the relationship between INR control and the rates of death, bleeding, MI, and stroke or SEE among 3587 patients with atrial fibrillation randomized to receive warfarin treatment in the SPORTIF (Stroke Prevention Using an Oral Thrombin Inhibitor in Atrial Fibrillation) III and V trials. The mean±SD follow-up was 16.6±6.3 months. Patients were divided into 3 equal groups (those with good control [75%], those with moderate control [60%-75%], or those with poor control [60%]) according to the percentage time with an INR of 2.0 to 3.0. Outcomes were compared according to INR control. The main outcome measures were death, bleeding, MI, and stroke or SEE. Results:The poor control group had higher rates of annualmortality(4.20%)andmajorbleeding(3.85%)comparedwiththemoderatecontrolgroup(1.84%and1.96%, respectively) and the good control group (1.69% and 1.58%, respectively) (P.01 for all). Compared with the good control group, the poor control group had higher ratesofMI(1.38%vs0.62%,P=.04)andofstrokeorSEE (2.10% vs 1.07%, P=.02). Conclusions: In patients with atrial fibrillation taking warfarin,therisksofdeath,MI,majorbleeding,andstroke or SEE are related to INR control. Good INR control is important to improve patient outcomes.
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Harvey D. White (2007) conducted an RCT in atrial fibrillation (n=3,587). Poor INR control (<60% time in therapeutic range) vs. Good INR control (>75% time in therapeutic range) was evaluated on stroke or systemic embolism event (SEE) (p=.02). Poor INR control in patients with atrial fibrillation taking warfarin was associated with higher rates of stroke or systemic embolism compared to good control (2.10% vs 1.07%, P=.02).
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