SPONTANEOUS PLATELET-AGGREGATION IN CEREBROVASCULAR-DISEASE .2. FURTHER CHARACTERIZATION OF THE PLATELET DEFECT

  • 1 January 1979
    • journal article
    • research article
    • Vol. 41  (3) , 512-522
Abstract
Of 187 patients with transient ischemic attacks (TIA) or cerebral infarction (CI), 39% demonstrated in vitro spontaneous platelet aggregation (SPA). Of 176 normal subjects the incidence of in vitro SPA was 5%. SPA is associated with ADP-induced-hyperaggregability, i.e., the threshold concentration to induce 2nd wave aggregation is decreased. SPA depends on pH increase in platelet-rich plasma stirring in an aggregometer while concurrent ADP-induced-hyperaggregability is independent of pH change. SPA is associated with malondialdehyde production and the release of endogenous 5-hydroxytryptamine [5-HT] and Km and Vmax values for [14C]-5HT incorporation are normal. No gross abnormalities of the platelet membrane glycoproteins were apparent although occasionally glycoprotein III was increased. Abnormal platelet behavior in patients with TIA and CI was demonstrated in which the enzyme system involved in thromboxane production is sufficiently stimulated by stirring alone to induce aggregation of platelets and the release reaction. Acetylsalicylic acid abolished SPA and prolonged the bleeding time with characteristics similar to normal individuals. Plasma .beta.-thromboglobulin levels were significantly increased in the patients studied. No correlation was established with the incidence of in vitro SPA.