[Role of clopidogrel in acute coronary syndromes without ST-segment elevation].

Unstable angina and no ST-segment elevation myocardial infarction are acute coronary syndromes (ACS) typically characterized by minimal or little myocardial damage, but often heralding "classical" infarction or coronary death in the short or medium term. Coronary thrombi, mainly composed by platelets, are the major pathogenetic component of ACS and an effective therapeutic target. The hemostatic balance can be shifted towards an antithrombotic state in the clinical setting. Although the thrombogenic stimuli acting in each individual patient, their intensity as well as the prothrombotic factors that may contribute to an inappropriate thrombus growth, remain largely unknown. To this purpose the modulation of platelet aggregation is a particularly effective and practical therapeutic target. The availability of a new antiplatelet agent, clopidogrel, with a proven efficacy in the prevention of cardiovascular events, suggests the opportunity of reviewing the mechanisms of instability and the therapeutic strategies in patients with ACS. In this review we analyze: 1) the composition of coronary thrombi in patients with ACS, 2) the mechanisms of thrombus development and growth, 3) the mechanisms of platelet adhesion and aggregation, 4) the characteristics of clopidogrel, 5) the efficacy of the various therapeutic strategies, 6) the possible implications of the adjunctive therapy with clopidogrel for the treatment and prevention of cardiovascular events in ACS with no ST-segment elevation.