Prognostic role of platelet reactivity in patients with acute coronary syndromes

Despite dual antiplatelet treatment with aspirin and clopidogrel, patients with acute coronary syndromes (ACSs) remain at risk for recurrent cardiovascular events. This may be due, at least in part, to an incomplete response to clopidogrel, which is more frequent in ACS patients compared to stable patients because of massive platelet activation and increased platelet turnover. Currently, numerous laboratory-based methods and point-of-care tests are available to assess platelet reactivity. Several studies have tried to establish a standardized definition of high on-treatment platelet reactivity and to evaluate a correlation between this aggregometric phenomenon and clinical outcomes. Indeed a strong relationship between high on-treatment platelet reactivity and ischemic events was found, especially in high-risk ACS patients undergoing percutaneous coronary revascularization. Therefore, evaluation of platelet reactivity in this subset of patients may guide physicians to choose the best antiplatelet regimen for the individual patient avoiding both ischemic and bleeding complications. This was the rationale for tailored antiplatelet therapy pursued by utilization of different clopidogrel regimens, more potent P2Y12 receptor antagonists, or more extensive administration of glycoprotein IIb/IIIa inhibitors. To date, data from randomized studies addressing the concept of tailored antiplatelet therapy did not show any clinical benefit from a strategy based on platelet reactivity monitoring. However, as predominantly elective and stable patients were included into the latter studies, these results cannot be completely transferred into an ACS setting. This review summarizes current evidence about the potential role of platelet reactivity in the therapeutic management of patients with ACS.