Adding the oral anticoagulant rivaroxaban to standard therapy after a myocardial infarction (MI) or unstable angina significantly reduced the risk of death, according to a new study.

Researchers at Brigham and Women's Hospital (Boston, MA, USA) and in other institutions participating in the Anti-Xa Therapy to Lower Cardiovascular Events in Addition to Standard Therapy in Subjects with Acute Coronary Syndrome (ATLAS-ACS 2 TIMI 51) study randomized 15,526 patients to rivaroxaban 2.5 mg or 5 mg twice daily, or to matching placebo. The average age of the patients was 62, and about 75% were white males. About half of them had an ST-elevation MI (STEMI), 25% had non-ST-elevation MI, and 25% had unstable angina. Background medications included aspirin (99%), thienopyridine (93%), beta-blockers (66%), ACE inhibitor or ARB (40%), statin (84%), and calcium channel blocker (15%); 60% of the patients underwent revascularization with either coronary artery bypass graft (CABG) or stenting.

The results showed that patients randomized to 2.5 mg twice daily were 34% less likely to die from cardiovascular disease than patients in the placebo group were and 32% less likely to die from any cause. Analysis of the components of the primary efficacy endpoint showed that rivaroxaban had a hazard ratio of 0.80 for death from cardiovascular causes (included hemorrhage-related deaths), 0.85 for MI, and 1.24 for stroke (including ischemic hemorrhagic, and stroke of uncertain causes), when compared to placebo. There were more bleeding incidents in the rivaroxaban group (2.1% versus 0.6%) and the rate of intracranial bleeding was 0.6% versus 0.2%, but there was not a significant increase in fatal bleeding events. The study was published early online on November 2011, in the New England Journal of Medicine (NEJM).

“If the data from ATLAS ACS 2 TIMI 51 were extrapolated into clinical practice, we could potentially see one life saved for every 56 patients treated with this combination of therapies over a two year period,” said study coauthor C. Michael Gibson, MD.

Rivaroxaban is an oral anticoagulant invented and manufactured by Bayer (Leverkusen; Germany), which in a number of countries it is marketed as Xarelto. It is the first available orally active direct factor Xa inhibitor, acting directly upon Factor X in the coagulation cascade, without using antithrombin as a mediator. Rivaroxaban is well absorbed from the gut and maximum inhibition of factor Xa occurs four hours after a dose. The effects last 8–12 hours, but factor Xa activity does not return to normal within 24 hours, so once-daily dosing is possible.

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