COAGULANT ACTIVITIES OF PLATELETS IN CORONARY-ARTERY DISEASE

Platelets have been implicated in the pathogenesis of coronary artery disease, and a number of studies have examined platelet function and coagulation parameters in such patients. Platelet coagulant activities, volumes and aggregate ratios in 23 patients with chest pain, 7 of whom had normal coronary angiograms (group I) and 16 of whom had angiographically proven coronary artery disease (group II) were examined. There were no significant differences in the mean values for platelet volume or platelet aggregate ratios between the 2 groups. The platelet coagulant activities concerned with initiation and the early stages of intrinsic coagulation were significantly increased in patients in group II as compared with those in group I. No significant differences were noted between the 2 groups with respect to prothrombin time, partial thromboplastin time and plasma levels of fibrinogen and coagulation factors V and VIII. However, the mean activity in plasma of antithrombin III (but not the level of antithrombin III antigen) was significantly lower in patients of group II compared with group I. Overall, the observations provide evidence for an enhanced contribution of platelets to the intrinsic coagulation system in patients with coronary artery disease. The platelet coagulant hyperactivity noted in these patients may reflect a role of platelets in the pathogenesis of coronary artery disease or may be secondary to the underlying arterial disease.