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NOACs vs. Warfarin in Nonvalvular AF and Stroke/TIA Patients
Study Questions:
In patients with prior transient ischemic attack (TIA)/stroke and atrial fibrillation, what is the effectiveness and safety of each novel oral anticoagulant (NOAC) versus warfarin in routine clinical practice?
Methods:
The REAFFIRM study investigators queried a large administrative claims database, representing about 170 million insured US lives, using International Classification of Diseases, Ninth Revision codes and prescription records from January 2012 to June 2015. Patients included in this analysis had nonvalvular atrial fibrillation and a history of previous ischemic stroke or TIA and were newly initiated on one of apixaban, dabigatran, rivaroxaban, or warfarin. Given the retrospective design of this study, each NOAC patient was propensity score matched 1:1 to a warfarin patient in an attempt to minimize baseline differences between treatment groups. The primary effectiveness endpoint was combined ischemic stroke/intracranial hemorrhage (ICH).
Results:
The mean follow-up for each matched cohort was about 0.5 years. A total of 2,514 patients were included in the apixaban versus warfarin cohort, 1,962 patients were included in the dabigatran versus warfarin cohort, and 5,208 patients were included in the rivaroxaban versus warfarin cohort. There was no significant difference in the primary endpoint of combined ischemic stroke/ICH in the apixaban versus warfarin cohort (hazard ratio [HR], 0.70; 95% confidence interval [CI], 0.33-1.48) nor in the dabigatran versus warfarin cohort (HR, 0.53; 95% CI, 0.26-1.07). There was a lower risk of ischemic stroke/ICH in the rivaroxaban group compared with the warfarin group (HR, 0.45; 95% CI, 0.29-0.72). There was no significant difference in major bleeding or ICH between any NOAC and warfarin.
Conclusions:
Rivaroxaban was associated with a significantly lower risk of ischemic stroke/ICH compared with warfarin. Apixaban and dabigatran were associated with a nonsignificantly lower risk of ischemic stroke/ICH compared with warfarin. The statistical significance observed in the rivaroxaban versus warfarin cohort may be a result of its larger sample size. There was no significant difference in safety between any NOAC and warfarin.
Perspective:
This study, using insurance claims data, corroborates the results of the TIA/stroke subgroup analyses of the three previous randomized clinical trials of each NOAC versus warfarin (apixaban in ARISTOTLE, dabigatran in RE-LY, and rivaroxaban in ROCKET-AF), which suggested that NOACs are reasonable alternatives to warfarin in patients with atrial fibrillation and prior TIA/stroke. This study does not permit comparisons between the NOACs; only between each NOAC and warfarin.
Keywords: Anticoagulants, Arrhythmias, Cardiac, Atrial Fibrillation, International Classification of Diseases, Intracranial Hemorrhages, Ischemic Attack, Transient, Secondary Prevention, Stroke, Warfarin, Vitamin K, Vascular Diseases
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