ANTECEDENT ASPIRIN THERAPY INHIBITS BASE-LINE PLATELET ACTIVITY IN PATIENTS PRESENTING WITH ACUTE MYOCARDIAL-INFARCTION

Aspirin therapy and platelet inhibition reduce the risk for the develo pment of acute myocardial infarction (AMI). However, the effects of as pirin on baseline platelet activity in patients presenting with AMI ar e not known. We determined the effect of long-term aspirin use on base line platelet activity in patients presenting with AMI, enrolled in th e GUSTO-III Platelet Study. Platelet characteristics were investigated by aggregometry, flow cytometry and enzyme-linked immunosorbent assay in 23 patients before thrombolysis. Sixteen AMI patients were aspirin free, and 7 patients were using aspirin (81-500 mg/daily). The aspiri n-treated patients exhibited a mild but consistent reduction of platel et activity which reached significance for 5 mu M (p = 0.02), and 10 m u M (p = 0.01) adenosine diphosphate induced aggregation. The surface expression of P-selectin (p = 0.02) and PECAM-1 (p = 0.03) and the pla sma level of soluble P-selectin (p = 0.02) were also reduced. As previ ously observed in normal humans and patients with stable coronary arte ry disease, long-term aspirin therapy is also associated with diminish ed platelet activation in patients presenting with AMI. Long-term aspi rin therapy mildly reduces baseline pla.telet activity; however, this degree of relative platelet inhibition does not appear to be cardiopro tective.