NEW YORK - In the early months of anticoagulant treatment, patients with nonvalvular atrial fibrillation (nvAF) have similar rates of bleeding and arterial clots with dabigatran, rivaroxaban and vitamin K antagonists (VKA) like warfarin, researchers from France report.
Large randomized trials have shown the newer non-VKA oral anticoagulants (NOAC) to have superior safety and efficacy relative to warfarin, but subsequent observational studies have yielded conflicting results.
Dr. Géric Maura from National Health Insurance (CNAMTS) in Paris and colleagues used the French National Health Insurance information system to assess the bleeding and arterial thrombotic risks of dabigatran and rivaroxaban, each compared with VKA, during the first few months of therapy in 32,807 newly treated patients with nvAF.
There was no significant difference in bleeding between VKA- and dabigatran- or rivaroxaban-treated patients on propensity-matched analysis, regardless of whether patients were treated with low or high doses of each NOAC, the researchers report in Circulation, online July 21.
The composite outcome comprising hospitalization for bleeding and death occurred with similar frequency in the different treatment groups.
Among the secondary endpoints, there were no significant differences between treatments in arterial thromboembolic events or in the composite outcome comprising stroke, systemic embolism and death.
"Although our overall results are reassuring in relation to initiation of NOAC in nvAF patients in France with no marked excess thromboembolic or bleeding risk, they also suggest that particular caution is required when initiating NOAC," the researchers conclude. "But on the basis of this study comparing NOAC to VKA, NOAC cannot be considered to be safer than VKA during the early phase of treatment. On the contrary, the clinical implications of our results are that physicians must be just as cautious when initiating NOAC as when initiating VKA, particularly in view of the absence of an antidote and objective monitoring of the extent of anticoagulation."
"Similar analyses should be extended to other NOAC such as apixaban and observational studies should now focus on NOAC head-to-head comparison in a non-inferiority design," they suggest.
The study had no commercial funding and the authors reported no conflicts of interest.
Dr. Maura did not respond to a request for comment.