Platelet Function following Acute Cerebral Ischemia

BACKGROUND: Studies have previously identified increased levels of platelet activation following acute ischemic stroke. In order to evaluate new antiplatelet agents and their combinations, there is a need for accurate measures of platelet activation. METHODS: Blood was taken from 17 patients within 24 hours of an acute ischemic stroke, and then at 3, 7, 14 and 42 days. For comparison, a group of 18 stable arteriopaths had identical tests performed. Platelet aggregation was measured using a free platelet counting technique, and platelet surface P-selectin and monocyte platelet aggregates (MPAs) were measured using flow cytometry. Soluble P-selectin and D-dimers were measured by an enzyme linked immune assay. RESULTS: The initial level of MPAs was significantly raised in the stroke patients compared with the stable patients (p = 0.04, 14.2% vs. 9.3%); however, this difference was not significantly higher than later study points (14.2%, 10.1%, 9.3%, 11.9%, 11.3%; days 1, 3, 7, 14 and 42 respectively. Day 1 vs. day 7 p = 0.07 ANOVA). No changes in P-selectin or platelet aggregation were identified. D-dimer levels were significantly higher on day 7 than day 42 (p < 0.01), and fibrinogen levels were elevated on both days 3 and 14 compared with day 42. Fibrinogen levels were not elevated compared with stable patients. CONCLUSIONS: MPA levels are elevated following an acute ischemic stroke compared to stable patients, but no significant change was seen with other platelet markers. This study suggests MPAs are a more sensitive marker of platelet activation than either P-selectin or aggregation.