Role of antiplatelet agents in the primary and secondary prevention of atherothrombotic events in high risk-patients.

Atherothrombosis describes the superimposition of a thrombus on a ruptured atherosclerotic plaque, and is the primary cause of acute ischemic events. Atherothrombosis is a generalized and progressive process with an inflammatory component. Patients with disease in one vascular bed are at risk of disease in another, a concept known as "cross-risk." Platelet adhesion, activation, and aggregation in the final stage of atherothrombosis are ultimately responsible for arterial occlusion and consequent ischemia. Therefore, antiplatelet therapy is an effective treatment choice for secondary prevention. Clopidogrel, an adenosine diphosphate receptor antagonist, given alone or in combination with aspirin, may benefit secondary prevention of ischemic events. Current treatment guidelines suggest the use of a combination of these two agents for secondary prevention where appropriate. However, data conflict regarding the efficacy of antiplatelet therapy for primary prevention. A recent meta-analysis demonstrated that aspirin significantly reduces the risk of first myocardial infarction in both men and women. The recent Clopidogrel for High Atherothrombotic Risk and Ischemic Stabilization, Management, and Avoidance trial, which evaluated the effects of clopidogrel plus aspirin compared with aspirin alone, seems to support the use of dual antiplatelet therapy in secondary prevention, but suggests that it may not be more effective than aspirin alone in primary prevention.