Echo-lucency of computerized ultrasound images of carotid atherosclerotic plaques are associated with increased levels of triglyceride- rich lipoproteins as well as increased plaque lipid content

Abstract

Background-Echo-lucency of carotid atherosclerotic plaques on computerized ultrasound B-mode images has been associated with a high incidence of brain infarcts as evaluated on CT scans. We tested the hypotheses that triglyceride-rich lipoproteins in the fasting and postprandial state predict carotid plaque echo-lucency and that echo-lucency predicts a high plaque lipid content. Methods and Results-The study included 137 patients with neurological symptoms and ≤50% stenosis of the relevant carotid artery. High-resolution B-mode ultrasound images of carotid plaques were computer processed to yield a measure of echogenicity (gray-scale level). Lipoproteins were measured before and hourly for 4 hours after a standardized fatty meal. A subgroup of 58 patients underwent endarterectomy. On linear regression analysis, echo-lucency (low gray-scale level) was associated with elevated levels of fasting and postprandial plasma triglycerides (P=.0002 and P=.002), IDL cholesterol (P=.0009 and P=.006), and VLDL/chylomicron remnant cholesterol (P=.0003 and P=.0004) and triglycerides (P=.0003 and P=.003), the area under the plasma triglyceride curve 0 to 4 hours after a fatty meal (P=.001), and body mass index (P=.0001). On ANCOVA, body mass index, fasting IDL cholesterol, and fasting plasma triglycerides were independent predictors of echo-lucency. Echo-lucency was associated with increased relative plaque lipid content (P=.02). Conclusions-Increased plasma levels of triglyceride-rich lipoproteins predict echo-lucency of carotid plaques, which is associated with increased plaque lipid content. Because echo-lucency has been associated with a high incidence of brain infarcts on CT scans, triglyceride-rich lipoproteins may predict a plaque type particularly vulnerable to rupture.