Possible existence of platelet activation before the onset of cerebral infarction.

To study the existence of platelet activation before the onset of cerebral infarction, the ultrastructural features of platelets (7-day survival) and coagulation-fibrinolytic markers (70-100-min life span) were measured 2-12 h (acute phase), 7 days (subacute phase) and 6 months (chronic phase) after onset in 18 patients with cerebral infarction. Seven patients with atherosclerosis but without cerebral infarction and eight healthy subjects were studied as controls. Ultrastructural study included folds, pseudopods, vacuoles and centralization in addition to immunochemical staining such as platelet peroxidase and fibrinogen. Furthermore, beta-thromboglobulin, platelet factor-4, thrombin antithrombin complex and alpha(2)-plasmin inhibitor plasmin complex were examined as coagulation-fibrinolytic markers. Ultrastructural study of circulating platelets demonstrated no difference between acute and chronic phases and little difference between cerebral infarction and atherosclerosis, although plasma coagulation-fibrinolytic markers showed an increase in cerebral infarction at the acute phase but no difference among the chronic phase of cerebral infarction, atherosclerosis and normal healthy subjects. It is considered that shape change in circulating platelets was caused by pre-existed atherosclerosis rather than the thrombotic event itself though coagulation-fibrinolytic markers were derived from the thrombotic event.