NEW ORLEANS – For patients with atrial fibrillation and either a recent acute coronary syndrome or percutaneous coronary intervention, combined treatment for 6 months with the anticoagulant apixaban and a P2Y12 inhibitor antiplatelet drug, but without aspirin, was safer than and as effective as a regimen that either also included aspirin or that substituted a vitamin K antagonist, such as warfarin, for the direct-acting oral anticoagulant, based on results from a multicenter, randomized trial with more than 4,600 patients.
The apixaban plus P2Y12 inhibitor (typically, clopidogrel) combination “resulted in less bleeding and fewer hospitalizations without significant differences in ischemic events than regimens that included a vitamin K antagonist, aspirin, or both,”, said at the annual meeting of the American College of Cardiology. Concurrently, his report of the results also appeared in an .
This finding in the AUGUSTUS trial gives clinicians more guidance for the long-standing dilemma of how to best prevent arterial thrombus formation in patients with atrial fibrillation (AFib). To prevent a stroke, these patients routinely receive treatment with an anticoagulant when they have an acute coronary syndrome (ACS) event or undergo percutaneous coronary intervention (PCI). Typically, they receive several months of dual antiplatelet therapy with aspirin plus a P2Y12 inhibitor to prevent a clot from forming in the stented or unstable region of a coronary artery.
These patients are not uncommon; this circumstance occurs for about 20% of all AFib patients, and poses the question of what is the safest and most effective way to treat them. Should they get triple therapy with an anticoagulant, aspirin, and a P2Y12 inhibitor, an option that could cause excess bleeding; or should one of the three drugs drop out with the potential for an increased rate of ischemic events? The AUGUSTUS findings suggest that one solution is treatment with a combination of the direct-acting oral anticoagulant apixaban () and the P2Y12 inhibitor clopidogrel ( ) but without aspirin.
For the majority of patients like the ones enrolled, “less is more.” By dropping aspirin from the treatment mix, patients did better, said Dr. Lopes, a professor of medicine at Duke University in Durham, N.C.
Dr. Lopes and his associates designed(A Study of Apixaban in Patients With Atrial Fibrillation, Not Caused by a Heart Valve Problem, Who Are at Risk for Thrombosis [Blood Clots] Due to Having Had a Recent Coronary Event, Such as a Heart Attack or a Procedure to Open the Vessels of the Heart) as a two-by-two factorial study to address two different questions: During 6 months of treatment, how did apixaban compare with a vitamin K antagonist (usually warfarin) in these patients for safety and efficacy, and how did aspirin compare with placebo in this setting for the same endpoints?
The trial enrolled 4,614 patients at 492 sites in 33 countries. All patients in the study received a P2Y12 inhibitor, with 93% treated with clopidogrel. The study had roughly as many patients as the combined total of patients enrolled in two smaller, prior studies that had looked at roughly the same questions in similar patients.
“The aspirin part is the more interesting, and probably more unique and important finding,”, a coinvestigator on the study, said in a video interview. Regardless of the anticoagulant used, patients who received aspirin had a 16% rate of major bleeds or clinically relevant non-major bleeds, compared with a 9% rate among those on placebo, a statistically significant result that underscored the bleeding risk posed by adding aspirin to an anticoagulant and a P2Y12 inhibitor.
The results also showed no statistically significant difference in any efficacy measure with or without aspirin, including the rate of death or hospitalization, or of any individual ischemic endpoint. However the results showed a signal of a small increase in the rates of each of three types of ischemic events – stent thrombosis, MI, and need for urgent revascularization, each of which showed a numerical increase when aspirin was dropped. But the increase was small.
Dr. Lopes calculated that, for example, to prevent one episode of stent thrombosis by treating with aspirin also would cause 15 major or clinically relevant non-major bleeds, which makes inclusion of aspirin something of a judgment call for each patient, said Dr. Alexander, a professor of medicine at Duke. An AFib patient with a high risk for thrombosis but a low risk for bleeding following PCI or an ACS event might be a reasonable patient to treat with aspirin along with apixaban and a P2Y12 inhibitor, he explained.
The rate of major or clinically relevant bleeds was 11% with apixaban and 15% with a vitamin K antagonist, a statistically significant difference. Patients treated with apixaban also had a significantly reduced rate of death or hospitalization, 24%, compared with 27% among those on the vitamin K antagonist, as well as a significantly lower rate of stroke.
Overall the lowest bleeding rate was in patients on apixaban but no aspirin, a 7% rate, while the highest rate was in patients on a vitamin K antagonist plus aspirin, a 19% rate.
Dr. Alexander said that it would be an overreach to extrapolate these findings to other direct-acting oral anticoagulants, compared with a vitamin K antagonist, but he believed that the findings the study generated about aspirin were probably relevant regardless of the anticoagulant used.