Clinical significance of thrombocytopenia during a non-ST-elevation acute coronary syndrome. The platelet glycoprotein IIb/IIIa in unstable angina: receptor suppression using integrilin therapy (PURSUIT) trial experience.

BACKGROUND The significance of thrombocytopenia in patients experiencing an acute coronary syndrome (ACS) has not been examined systematically. We evaluated this condition in a large non-ST-elevation ACS clinical trial, with particular interest paid to its correlation with clinical outcomes. METHODS AND RESULTS Patients presenting without persistent ST elevation during an ACS were randomized to receive a double-blind infusion of the platelet glycoprotein (GP) IIb/IIIa inhibitor eptifibatide or placebo in addition to other standard therapies including heparin and aspirin. The primary end point was death/nonfatal myocardial infarction (MI) at 30 days, whereas bleeding and stroke were the main safety outcomes. Thrombocytopenia (nadir platelet count <100x10(9)/L or <50% of baseline) occurred in 7.0% of enrolled patients. The time to onset was a median of 4 days in both treatment arms. Patients with thrombocytopenia were older, weighed less, were more likely nonwhite, and had more cardiac risk factors. These patients experienced significantly more bleeding events: they were more than twice as likely to experience moderate/severe bleeding after adjustment for confounders. Univariably, ischemic events (stroke, MI, and death) occurred significantly (P<0.001) more frequently in patients with thrombocytopenia; multivariable regression modeling preserved this association with death/nonfatal MI at 30 days. Neither the use of heparin or eptifibatide was found to independently increase thrombocytopenic risk. CONCLUSIONS Although causality between thrombocytopenia and adverse clinical events could not be established definitively, thrombocytopenia was highly correlated with both bleeding and ischemic events, and the presence of this condition identified a more-at-risk patient population.