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OASIS-6: Fondaparinux superior to unfractionated heparin
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ATLANTA — The low-molecular weight heparin fondaparinux significantly reduced mortality and recurrent myocardial infarction in STEMI patients without increasing bleeding in comparison with unfractionated heparin in the OASIS-6 trial.
OASIS-6 (MICHELANGELO: Organization to Assess Strategies in Ischemic Syndromes) was a double-blind, double-dummy trial that included 12,000 patients with STEMI reporting <12 hours from symptom onset. Shamir P. Mehta, MD, and Salim Yusuf, MD, both from McMaster University, Canada, presented the trial design and results at the American College of Cardiology Scientific Session 2006.
Factor Xa inhibitor
Mehta said that fondaparinux (Arixtra, GlaxoSmithKline) was a factor Xa inhibitor that is given in a once-daily fixed 2.5 mg dose without monitoring. It has previously demonstrated efficacy in patients with peripheral artery disease and acute coronary syndromes. In both venous thromboembolism prevention and bleeding risks in patients with unstable angina/NSTEMI, fondaparinux has shown superiority to enoxaparin. However, the role of current antithrombotics in STEMI remains unclear, and there are concerns about increased bleeding and intracranial hemorrhage, he said.
The OASIS-6 evaluated the safety and efficacy of fondaparinux vs. usual care with unfractionated heparin or placebo. Initial treatment was lytics, primary PCI or no reperfusion. Patients with a contraindication for unfractionated heparin were randomized to 2.5 mg of fondaparinux or placebo. Patients who had indications for unfractionated heparin were randomized to fondaparinux 2.5 mg or unfractionated heparin. Death or MI at 30 days was the primary efficacy outcome, and severe bleeding the primary safety outcome.
Bleeding rate lower
The primary efficacy outcome occurred in 11.2% of control group patients and in 9.7% of patients given fondaparinux (HR 0.86, P=.008). Differences were apparent for fondaparinux vs. both unfractionated heparin and placebo controls. Death was 8.9% in the control groups and 7.8% for fondaparinux (P=.026).
Significant differences (P=.003) were apparent by the end of treatment at day nine. Bleeding — severe hemorrhage at nine days — was lower in the fondaparinux arms (HR, 0.77, P=.13) and intracranial hemorrhage was similar for both groups. There was no benefit with fondaparinux in primary PCI.
Yusuf concluded that fondaparinux significantly reduced mortality and recurrent MI in STEMI without increasing bleeding compared to placebo or unfractionated heparin. Mortality was significantly reduced. – by Walter Alexander
For more information:
- Yusuf S, Mehta SR. The impact of fondaparinux, a synthetic factor Xa inhibitor on mortality and reinfarction in patients with acute ST segment elevation myocardial infarction: results of the Michelangelo-Organization to Assess Strategies for Ischemic Syndromes (OASIS)-6 trial. Presented at the American College of Cardiology Scientific Session 2006. March 11-14, 2006. Atlanta.