Antiplatelet drug response variability and the role of platelet function testing: a practical guide for interventional cardiologists.

Antiplatelet therapy is the cornerstone of treatment for patients with acute coronary syndrome and is also of particular importance in those who undergo percutaneous coronary intervention with stent implantation. Dual antiplatelet therapy with aspirin and clopidogrel is associated with improvement in long-term clinical outcomes in such patients and is presently the antiplatelet therapy of choice for secondary prevention of thrombotic events. However, a significant number of patients experience recurrent events despite antiplatelet therapy. Although poor patient compliance can account for some of these events, particularly in those patients who receive a drug-eluting stent, increasing evidence indicates that there is variability in response to antiplatelet therapy and patients who have higher levels of platelet reactivity are at increased risk for recurrent ischemic events. However, the lack of a consistent definition of inadequate platelet response, as well as the lack of a standardized measurement technique, has made it difficult to define how to treat these patients. To translate findings associated with variability in platelet response into improved patient care, it is necessary to gain a better understanding of what variable platelet response is, how it is measured, who it should be measured in, and what its clinical relevance is. The objective of this review is to evaluate the data regarding interindividual response variability to antiplatelet therapy with the aim of providing practical considerations and where possible, recommendations, regarding this topic for interventional cardiologists.