Oral Anticoagulant Stroke Risk in Atrial Fibrllation
Patients taking apixaban were more likely to experience ischemic stroke or systemic embolism vs patients taking warfarin.
Apixaban 2.5 mg twice daily was associated with higher rates of ischemic stroke or systemic embolism compared with warfarin in patients with nonvalvular atrial fibrillation, according to a study published in the BMJ. Rivaroxaban 15 mg once a day and dabigatran 110 mg twice a day showed evidence of lower thromboembolic rates.
Torben Bjerregaard Larson, from the Aalborg Thrombosis Research Unit, Department of Clinical Medicine, Faculty of Health, Aalborg University, Denmark, and colleagues sought to examine the effectiveness and safety of apixaban, dabigatran, and rivaroxaban compared with warfarin in patients with atrial fibrillation who had not previously taken an oral anticoagulant.
“It might be important to review concerns about safety of oral anticoagulant treatment in atrial fibrillation: ineffective or insufficient treatment for stroke prevention should be viewed as a safety issue itself, while the increase in the risk of bleeding is an inevitable consequence of a necessary treatment,” the study authors noted. “Thus, choosing the appropriate antithrombotic agent for each individual is paramount to reduce the stroke burden in atrial fibrillation, while a relative increase in risk of bleeding cannot be ruled out.”
The researchers included 55,644 patients (mean age, 73.9) with nonvalvular atrial fibrillation filling a first prescription for an oral anticoagulant from August 2011 to February 2016. The participants were treated with dabigatran 110 mg (n=8,875), rivaroxaban 15 mg (n=3,476), apixaban 2.5 mg (n=4,400), or warfarin (n=38,893).
After a 1-year follow-up period, apixaban was associated with a higher weighted event rate of ischemic stroke/systemic embolism (4.8%) than dabigatran (3.3%), rivaroxaban (3.5%), and warfarin (3.7%).
Compared with warfarin, apixaban was associated with a nonsignificant trend for higher rates of ischemic stroke or systemic embolism (1-year hazard ratio [HR], 1.19). In addition, rivaroxaban (HR, 0.89) and dabigatran (HR, 0.89) were associated with a nonsignificant trend with lower rates after 1 year compared with warfarin.
The weighted event rates for bleeding outcomes were 5.6% for rivaroxaban, 5.1% for apixaban, 5.1% for warfarin, and 4.1% for dabigatran. The 1-year HR for bleeding for dabigatran compared with warfarin was 0.80. The HRs for apixaban and rivaroxaban compared with warfarin were 0.96 and 1.06.
Nielsen PB, Sjoth F, Sogaard M. Effectiveness and safety of reduced dose non-vitamin K antagonist oral anticoagulants and warfarin in patients with atrial fibrillation: propensity weighted nationwide cohort study. BMJ. 2017;356:j510. doi:10.1136/bmj.j510