Higher Levels of Interleukin-6 Are Associated With Lower Echogenicity of Carotid Artery Plaques

Abstract

Echo-lucent carotid plaques can be fragile and vulnerable to rupture, representing a risk factor for ischemic stroke. Given the studies showing that elevated levels of circulating inflammatory markers are predictive of cardiovascular events, we sought to determine whether higher levels of serum interleukin-6 (IL-6) and high-sensitivity C-reactive protein (hsCRP) are associated with lower echogenicity of carotid plaques. The study comprised 246 patients who had carotid atherosclerotic plaques as evidenced by ultrasound. Using acoustic densitometry, we quantified the echogenicity of the largest plaque in each patient by integrated backscatter analysis. Serum IL-6 and hsCRP levels were determined in all patients. Both log-transformed IL-6 and hsCRP concentrations were negatively correlated with carotid plaque echogenicity (r=-0.28, P<0.001, and r=-0.14, P<0.05, respectively). When traditional atherosclerotic risk factors, plaque thickness, and medication use were controlled for, IL-6 levels were inversely associated with plaque echogenicity (beta=-0.21, P<0.01), whereas such an association was of borderline significance for hsCRP (beta=-0.12, P=0.06). Higher IL-6 levels, in addition to hsCRP levels, appear to be associated with lower echogenicity of carotid plaques, suggesting a link between inflammation and potential risk of plaques.