Effect of increased time in the therapeutic range on atrial fibrillation outcomes within a centralized anticoagulation service

Abstract

BackgroundClinical pharmacy anticoagulation services have improved the quality of anticoagulant therapy and are associated with lower rates of bleeding and thromboembolism compared to usual care. Several studies have found that higher time-in-therapeutic range (TTR) during warfarin therapy is associated with better warfarin outcomes. However, whether increasing TTR over time within an established anticoagulation service is associated with further reduction in bleeding and thromboembolic outcomes is unknown. MethodsThis was a retrospective cohort study of patients with atrial fibrillation conducted at an integrated healthcare delivery system with a centralized, pharmacist-managed anticoagulation service. Clinical outcomes (clinically-relevant bleeding, ischemic stroke or systemic embolism, and all-cause mortality) and TTR were compared between two distinct time periods: 1/1/2006 through 12/31/2007 (control group) and 1/1/2012 through 12/31/2013 (observation group) with regression modeling to adjustment for potential confounders. ResultsThere were 3641 and 4764 patients in the control and observation groups, respectively. The mean age was 74.3 years and 54.4% of the cohort was female. Mean TTR was higher in the observation group (70.5% vs. 63.4%, p < 0.001). The composite outcome of clinically-relevant bleeding, thromboembolism and all-cause mortality occurred in 4.6% and 3.6% of the control and observation groups, respectively (adjusted odds ratio = 0.69; 95% confidence interval 0.54–0.87). Individual rates of stroke/systemic embolism and all-cause mortality were each lower in the observation group (both p < 0.05) while clinically-relevant bleeding was not significantly different (p = 0.256). ConclusionIncreased TTR within a clinical pharmacy anticoagulation management service was associated with a lower risk of the composite outcomes of bleeding, thromboembolism and death in a large atrial fibrillation population receiving warfarin.