Abstract WP146: Degree of Carotid Stenosis is Associated with Coated-platelet Levels

Abstract

Background: Coated-platelets, a subset of procoagulant platelets observed upon dual agonist stimulation with collagen and thrombin, support a robust prothrombinase activity and provide a unique measure of platelet thrombotic potential. Coated-platelet levels are elevated in patients with non-lacunar ischemic stroke and decreased in patients with spontaneous intracerebral hemorrhage compared to controls. Because these findings suggest that extremes in coated-platelet levels may be associated with either thrombotic or hemorrhagic events, we investigated coated-platelet synthesis in symptomatic and asymptomatic patients with carotid artery stenosis. Methods: Coated-platelet levels were determined in 3 consecutively recruited groups: 1) patients with acute transient ischemic attack or stroke and ≥50% ipsilateral internal carotid artery stenosis (n=45); 2) asymptomatic patients with ≥50% carotid stenosis (n=68), and 3) asymptomatic patients with <50% carotid stenosis (n=92). Results are reported as percent of cells converted to coated-platelets. Differences between groups were assessed using independent t-tests and Fisher’s exact tests. The relationship between group and coated-platelet levels was assessed with a three-way ANOVA and Tukey’s HSD test. Results: Coated-platelet levels (mean±SD) differed among the groups (F = 5.12, p = 0.007) with significant elevations among symptomatic carotid stenosis patients (39.5±16.3, p = 0.003) and asymptomatic ≥50% carotid stenosis patients (37.1±12.6, p = 0.028) compared to <50% carotid stenosis patients (32.5 ± 11.5).These differences remained significant after adjusting for age and medication use (F=5.07, p<0.0001). No significant difference was noted between symptomatic and asymptomatic carotid stenosis patients with ≥50% stenosis (p = 0.33). Conclusions: These results suggest that the presence of ≥50% carotid stenosis is associated with an increase in platelet prothrombotic potential. Further study of coated-platelet levels in patients with asymptomatic carotid stenosis is warranted to assess for an association with stroke incidence.