Coagulation activation and ultrasound characteristics in patients with carotid artery disease

INTRODUCTION: Elevated levels of markers for thrombin activation are associated with plaque echogenicity and degree of stenosis in patients with carotid artery stenosis. The Activated Protein C-Protein C Inhibitor (APC-PCI) complex reflects activation of the Protein C system and is a measure of thrombin generation. The aim of the present study was to examine APC-PCI complex in patients undergoing thrombendartherectomy for carotid artery stenosis, and to relate the findings to clinical characteristics and plaque morphology as determined by ultrasound.

MATERIALS AND METHODS: Blood was obtained from 125 patients (39 female, median age 71 years) with carotid artery stenosis admitted from September 2005 to May 2007. The APC-PCI complex was measured using a sandwich immunofluorometric method and compared to an age- and sex-matched healthy control-group. Clinical and demographic characteristics, routine laboratory markers and ultrasound characteristics were analysed using univariate and multivariate analysis.

RESULTS: APC-PCI complex concentration was significantly increased in patients with carotid artery stenosis (median 0.21 microg/L; 10th to 90th percentile 0.15-0.36) compared to a healthy control-group (0.19 microg/L; 0.11-0.31; P=.009). There was no significant difference in APC-PCI-values between asymptomatic (n=48) and symptomatic (n=77) patients with carotid artery stenosis (0.22 vs. 0.20 microg/L; p=0.626). Patients with minor stroke (n=31) had a higher median APC-PCI-concentration (0.27 microg/L; 0.15-0.63) than patients with amaurosis fugax (0.19 microg/L; 0.15-0.36) or transient ischemic attack (0.21 microg/L; 0.12-0.36) (p=0.016). No association was found between APC-PCI-values and the degrees of carotid artery stenosis or the time from the latest neurological symptoms to blood sampling. Patients with echolucent plaques had significantly lower APC-PCI concentrations (0.20 microg/L; 0.14-0.35 vs. 0.24 microg/L; 0.15-0.60; p=0.043), according to the Gray-Weale classification.

CONCLUSIONS: Patients with carotid artery disease exhibit increased concentrations of APC-PCI compared to a healthy control-group, particularly those patients with echogenic plaques, who have significantly higher APC-PCI levels than patients with echolucent plaques.