Results from the ANTARCTIC study, which was simultaneously presented at the 2016 European Society of Cardiology congress (27–31 August, Rome, Italy) and published in The Lancet, indicate that monitoring platelet function in elderly patients with acute coronary syndromes does not significantly improve clinical outcomes. Previous studies have shown that platelet monitoring does not benefit younger, lower risk patients.
A previous study—ARCTIC—has already shown that platelet function monitoring does not improve clinical outcome in low-risk patients undergoing elective percutaneous coronary intervention (PCI). But Guillaume Cayle (Service de Cardiologie, Centre Hospitalier Universitaire de Nimes, Université de Montpellier, Nimes, France) and others, writing in The Lancet, note that a limitation of this study was that the patients were lower risk and that platelet monitoring may be more beneficial for higher risk patients. Therefore in ANTARCTIC, they evaluated the use of platelet monitoring in patients aged 75 years or older undergoing PCI for acute coronary syndrome.
Of the 877 patients enrolled in the study, 442 were randomised to conventional therapy (no adjustment) and 435 were randomised to monitoring and treatment adjustment (if needed). All patients were started on 5mg prasugrel (Efient, Daiichi Sankyo), but treatment was changed in approximately 45% of patients in the monitoring group—with 39% of patients being switched to clopidogrel because they were found to have low on-treatment platelet reactivity and 4% being switched to 10mg prasugrel because they were found to have high platelet reactivity.
The primary endpoint was a composite of cardiovascular death, myocardial infarction, stroke, stent thrombosis, urgent revascularisation and bleeding complication at one year. Cayle et al report that there were no significant differences between groups in this endpoint: 27.6% for the monitoring group vs. 27.8% for the conventional group (p=0.98). Additionally, there was not a significant difference in rate of the main secondary endpoint (a composite of cardiovascular death, myocardial infarction, stent thrombosis or urgent revascularisation), which occurred in 9.9% and 9.3%, respectively (P=0.80).
Gilles Montalescot (Hôpital Pitié-Salpêtrière, in Paris, France), who presented the study during a hot line session at the ESC, says: “Platelet function testing is still being used in many centres to measure the effect of antiplatelet drugs and adjust the choice of these drugs and their doses. Our study does not support this practice and these recommendations. Although measuring the effect of antiplatelet agents makes sense in order to choose the best drugs or doses, this costly and more complex strategy does not appear to benefit patients, even when they present with extremely high risk of ischaemic and bleeding events liked those enrolled in ANTARCTIC.”
He adds: “ANTARCTIC confirms the ARCTIC study in a different population with a different drug, and has addressed the potential limitations of the ARCTIC study, but finally reached the same conclusion. I expect there will be adjustments of guidelines and practice in light of this.”