Can NOACs 'Compete' with Well-Managed Warfarin Treatment? Retrospective Data from Swedish Registers
The efficacy and safety of new oral anticoagulants (NOACs) in stroke prevention in atrial fibrillation have been proven by numerous studies. The quality of warfarin treatment, assessed by the 'time in therapeutic range' (TTR), ranged between 55% and 65% in these studies. The work of Swedish authors provides a comparison of patients treated with NOACs to a group on warfarin whose average TTR reached 70%.
Stroke Prevention in Atrial Fibrillation
Atrial fibrillation is a significant risk factor for ischemic stroke. Administration of vitamin K antagonists reduces this risk by about two-thirds but also increases the risk of bleeding. In the last decade, 'new,' non-vitamin K-dependent anticoagulants (NOACs) have appeared on the market. These act through direct inhibition of thrombin (dabigatran) or coagulation factor Xa (rivaroxaban, apixaban, edoxaban). In numerous key clinical studies, these agents have demonstrated equal or better efficacy in preventing ischemic stroke and systemic embolization in atrial fibrillation while providing equal or higher safety compared to vitamin K antagonists.
Data from the Swedish Registry
Swedish authors utilized information from the national registry and conducted a retrospective study comparing the efficacy and safety of three NOACs (apixaban, dabigatran, and rivaroxaban) and warfarin in patients with non-valvular atrial fibrillation. The study included data on 12,694 patients who started NOAC therapy between July 2011 and December 2014. The control group consisted of 36,317 patients who initiated warfarin treatment. The number of thromboembolic events and bleeding incidents requiring hospitalization or leading to death were evaluated.
Findings
The average age of patients was 72.2 years in the NOAC group and 72.3 years in the warfarin group. The average duration of follow-up was 299 and 283 days, respectively. In the NOAC group, dabigatran was used in 40.3% of cases, rivaroxaban in 31.2%, and apixaban in 28.5%. In the warfarin-treated group, the time in therapeutic range, defined as the percentage of days with INR within the target range of 2.0–3.0, was around 70%.
No significant difference was found in the overall number of strokes and thromboembolic events or in the number of gastrointestinal bleeding episodes. However, patients treated with NOACs experienced less frequent severe bleeding overall (hazard ratio [HR] 0.78; 95% confidence interval [CI] 0.67–0.92), intracranial bleeding (HR 0.59; 95% CI 0.40–0.87), hemorrhagic stroke (HR 0.49; 95% CI 0.28–0.86), and other unspecified severe bleeding (HR 0.71; 95% CI 0.57–0.89).
Conclusion
The study demonstrated that NOACs are as effective as well-managed warfarin in preventing stroke in patients with atrial fibrillation, with fewer episodes of severe bleeding occurring during NOAC treatment.
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Source: Sjögren V., Byström B., Renlund H. et al. Non-vitamin K oral anticoagulants are non-inferior for stroke prevention but cause fewer major bleedings than well-managed warfarin: a retrospective register study. PLoS One 2017; 12 (7): e0181000, doi: 10.1371/journal.pone.0181000.
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