A new study claims that atrial fibrillation (AF) patients treated with the investigational factor Xa inhibitor apixaban had fewer strokes or embolic events, fewer major bleeding events, and were less likely to die when compared to treatment with warfarin.

Researchers at Duke University Medical Center (DUMC; Durham, NC, USA) and other institutions participating in the Apixaban for the Prevention of Stroke in Subjects with Atrial Fibrillation (ARISTOTLE) study conducted a randomized, double-blind trial to compare apixaban with warfarin in 18,201 patients with AF, and at least one additional risk factor for stroke. The primary outcome was ischemic or hemorrhagic stroke, or systemic embolism, with key secondary objectives of testing for superiority with respect to the primary outcome and to the rates of major bleeding and death from any cause. The median duration of follow-up was 1.8 years.

The results showed that the rate of the primary outcome was 1.27% per year in the apixaban group, as compared with 1.60% per year in the warfarin group. The rate of major bleeding was 2.13% per year in the apixaban group, compared to 3.09% per year in the warfarin group; the rates of death from any cause were 3.52% and 3.94%, respectively, and the rate of hemorrhagic stroke was 0.24% per year in the apixaban group, as compared with 0.47% per year in the warfarin group. Finally, the rate of ischemic or uncertain type of stroke was 0.97% per year in the apixaban group, and 1.05% per year in the warfarin group. The study was published early online on August 27, 2011, in the New England Journal of Medicine.

“The primary outcome of stroke or systemic embolism occurred in 212 patients in the apixaban group as compared with 265 patients in the warfarin group,” concluded lead author Christopher Granger, MD, of the DUMC, and colleagues. “The lower risk of hemorrhagic stroke suggests there is a specific risk associated with warfarin, possibly related to its inhibition of multiple coagulation factors or interaction between warfarin and tissue factor VIIa complexes in the brain.”

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