Aspirin and Clopidogrel Resistance in Drug Eluting Stent Era

Platelets play a central role in the pathogenesis of atherothrombosis.Dual antiplatelet therapy with clopidogrel plus aspirin has been shown to reduce ischemic events in patients undergoing percutaneous coronary intervention (PCI) and stenting.Although dual antiplatelet therapy reduces the risk of cardiovascular episodes after PCIs, a substantial number of incidents continue to occur.Many cardiologists have focused their attention to the relationships between the interindividual variability of platelet inhibition after aspirin or clopidogrel administration and major cardiac adverse events such as stent thrombosis.Recent evidence has suggested that "aspirin or clopidogrel resistance" is associated with poor health outcomes (recurrent atherothrombotic events and stent thrombosis) after drug eluting stent (DES) implantation.However, the current clinical guidelines do not support routine screenings for antiplatelet resistance because standardized objective screening has not yet been established.Thus, this review describes the antiplatelet therapy used in PCI and it outlines the mechanism, laboratory tests, clinical impact and treatment options for aspirin and clopidogrel resistance in the DES era.(Korean Circulation J 2007;37:135-147) KEY WORDSPlateletsAspirinClopidogrelDrug resistanceStentsAngioplasty. Platelet activation and antiplatelet therapy in PCIPlatelet activation occurs in the patients who undergo PCI as a result of the PCI procedure itself and the underlying atherothrombotic disease.PCI techniques cause denudation of the arterial endothelium and mechanical disruption of the coronary plaque.Following exposure of the subendothium to circulating blood, there is extensive platelet adhesion, platelet activation and platelet aggregation(Fig.1). 12)13)Vascular injury and the accom-