Higher Leukocyte Count Is Associated with Lower Presence of Carotid Lipid-Rich Necrotic Core: A Sub-Study in the Plaque at RISK (PARISK) Study

Abstract

Background: Increasing evidence suggests that inflammation inside the vessel wall has a prominent role in atherosclerosis. In carotid atherosclerosis in particular, vulnerable plaque characteristics are strongly linked to an increased stroke risk. An association between leukocytes and plaque characteristics has not been investigated before and could help with gaining knowledge on the role of inflammation in plaque vulnerability, which could contribute to a new target for intervention. In this study, we investigated the association of the leukocyte count with carotid vulnerable plaque characteristics.

Methods: All patients from the Plaque At RISK (PARISK) study whom had complete data on their leukocyte count and CTA- and MRI-based plaque characteristics were included. Univariable logistic regression was used to detect associations of the leukocyte count with the separate plaque characteristics (intra-plaque haemorrhage (IPH), lipid-rich-necrotic core (LRNC), thin or ruptured fibrous cap (TRFC), plaque ulceration and plaque calcifications). Subsequently, other known risk factors for stroke were included as covariates in a multivariable logistic regression model.

Results: 161 patients were eligible for inclusion in this study. Forty-six (28.6%) of these patients were female with a mean age of 70 [IQR 64-74]. An association was found between a higher leukocyte count and lower prevalence of LRNC (OR 0.818 (95% CI 0.687-0.975)) while adjusting for covariates. No associations were found between the leucocyte count and the presence of IPH, TRFC, plaque ulceration or calcifications.

Conclusions: The leukocyte count is inversely associated with the presence of LRNC in the atherosclerotic carotid plaque in patients with a recently symptomatic carotid stenosis. The exact role of leukocytes and inflammation in plaque vulnerability deserves further attention.

Keywords: atherosclerosis; carotid stenosis; ischemic stroke; leukocyte; vulnerable plaque.

Figure 1

(A) Axial view of a 3D T1-weighted fast spoiled gradient echo MR image showing a high-intense signal (asterisk) indicative of intraplaque hemorrhage. (B) Axial view of a carotid plaque depicted with 3D T1-weighted pre-contrast quadruple inversion recovery MR, which is delineated to measure different plaque components. The part surrounded with a yellow line is a lipid-rich necrotic core. (C) CTA image showing several calcifications (arrow heads) in a carotid plaque of the ICA. (D) CTA image with contrast material reaching into a carotid plaque (arrow head), which indicates plaque ulceration. (E) Post-contrast T1-weighted fast spin echo MR image, which shows an interrupted signal (arrow head) between the lipid-rich necrotic core (asterisk) and the lumen of the ICA. (F) The orange arrow in this 3D T1-weighted pre-contrast quadruple inversion recovery MR image represents the maximum vessel wall area of this carotid plaque. CCA = common carotid artery, ECA = external carotid artery, and ICA = internal carotid artery. These images and legends were previously published by Van Dam-Nolen et al. as part of another PARISK paper [12].