Risk of ischemic stroke may be higher in afib patients on newer anticoagulants vs. on warfarin
The increase in stroke risk was particularly high among patients taking apixaban and dabigatran, whereas the results for rivaroxaban and edoxaban were more ambiguous.
The well-documented lower risk of bleeding with novel oral anticoagulants (NOACs) compared to warfarin may come at the price of a higher risk of ischemic stroke, according to a retrospective study.
Researchers used data from all patients with a diagnosis of atrial fibrillation who were hospitalized in 2015 and 2016 throughout the Hospital Corporation of America Healthcare network of U.S. hospitals. They compared the relative incidence of acute ischemic stroke among patients taking NOACs (n=67,262) and those taking warfarin (n=59,066) as home medications. They also compared individual NOACs to warfarin, as well as stroke severity between the two groups using National Institutes of Health Stroke Scale (NIHSS) scores at admission.
Results were published online on Oct. 15 by Stroke.
Overall, 3,812 NOAC patients and 2,626 warfarin patients had ischemic stroke. Patients with atrial fibrillation who were taking NOACs had a significantly higher incidence of ischemic stroke compared to those taking warfarin (odds ratio, 1.29; P<0.001). Patients taking warfarin had marginally greater stroke severity than those taking NOACs (mean NIHSS score, 5.23 vs. 4.78; P=0.011). In addition, the frequency of intracranial hemorrhages was consistently lower in those taking NOACs than in those taking warfarin (odds ratio, 0.71; P<0.001).
In comparisons of individual NOACs to warfarin, significantly more patients taking apixaban and dabigatran had ischemic stroke (odds ratios, 1.45 [P<0.001] and 1.29 [P<0.001], respectively). Odds ratios of stroke for patients taking rivaroxaban and edoxaban were also higher compared to warfarin (1.07 and 1.40, respectively) but were not statistically significant, although the small sample size of patients taking edoxaban accounted for the lack of difference.
The results suggest that compared to patients taking warfarin, “NOAC patients may be less strongly or less consistently anticoagulated, an interpretation consistent with lower ischemic stroke risk and elevated intracranial hemorrhage risk in patients who are strongly anticoagulated,” the study authors concluded. They added that monitoring levels of anticoagulation among patients taking NOACs “may be an important unfilled need in stroke prevention” and that phasing out warfarin use among patients with atrial fibrillation may be contraindicated in some circumstances.