Macrophages are associated with lipid-rich carotid artery plaques, echolucency on B-mode imaging, and elevated plasma lipid levels*1

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. (J Vasc Surg 2002;35:137-45.)