Abstract

Antiplatelet therapy is the keystone in secondary prevention of the patients with cardiovascular diseases. The efficacy of aspirin, clopidogrel and novel oral antiplatelets like prasugrel and ticagrelor in atherotrombotic events has been shown in several landmark clinical trials and meta-analyses. Nevertheless, a significant number of patients experience recurrent events despite antiplatelet therapy. Increasing evidence indicates that there is considerable variability in response to antiplatelet therapy among patients and those who have higher levels of platelet reactivity are at increased risk for recurrent ischaemic events. These findings raised the possibility that decreased response, or ‘resistance’ to oral antiplatelet drugs may underlie many subsequent major cardiovascular events (MACE). The main problem with ‘resistance’ is the lack of a clear definition. In this chapter, aspirin, clopidogrel and glycoprotein IIb/IIIa receptor inhibitor resistance in patients with acute coronary syndromes will be discussed by the concept of residual platelet activity.