Macrophages are associated with lipid-rich carotid artery plaques, echolucency on B-mode imaging, and elevated plasma lipid levels

Objective. Atherosclerosis may be regarded as an inflammatory disease dominated by macrophages. We tested whether macrophages in carotid artery atherosclerotic plaques are associated with echolucency on B-mode ultrasound imaging, lipid levels, inflammatory markers, and aspirin use. Methods: We studied 106 patients undergoing carotid endarterectomy having 50% carotid artery stenosis and previous ipsilateral hemispheric neurologic symptoms. Results. Macrophages were particularly common in plaques with a high content of lipid and hemorrhage and, conversely, rare in plaques dominated by calcification and fibrous tissue. Macrophage density in carotid artery plaques classified by B-mode ultrasound imaging as echolucent (n = 56), intermediate (n = 25), or echorich (n = 25) was 1.8% +/- 0.2%, 1.5% +/- +/- 0.4%, and 1.0% +/- 0.2% ( SE), respectively (analysis of variance, P = .02). A computer-generated measure of plaque echolucency, gray-scale median, was associated with increased macrophage density (r = -0.31; P = .002). Furthermore, plasma and low-density lipoprotein cholesterol levels were associated with carotid artery macrophage density (r = 0.26, P = .008 and r = 0.23, P = .02), this was most pronounced in patients with lipid-rich plaques Macrophage density was not associated with plasma levels of acute-phase reactants. Finally, macrophage density in carotid artery plaques of users (n = 55) and nonusers of aspirin (n = 51) was 1.2% +/- 0.2% and 1.8% +/- 0.2% (t test, P = .01). Conclusions. Increased macrophage density in carotid atherosclerotic plaques was associated with lipid content, plaque echolucency, and increased plasma and low-density lipoprotein cholesterol levels. Furthermore, use of aspirin was associated with reduced macrophage density in carotid artery plaques.