[Differences between men and women in the composition of atherosclerotic plaque, as an explanation for the lower success rate of carotid endarterectomy in women]

Abstract

Objective: To determine whether men and women differ in the histological characteristics of plaque material removed at carotid endarterectomy.

Design: Observational and descriptive.

Methods: Carotid endarterectomy plaque specimens obtained from 45 degrees consecutive patients (135 women, 315 men) were assessed for the presence of macrophages, smooth muscle cells, collagen, calcifications, and luminal thrombus by means ofimmunohistochemical staining. The plaques were categorised in 3 phenotypes according to the overall presentation of histological characteristics and the lipid level. Protein was isolated from the plaques to determine the interleukin-6 (IL-6) and IL-8 concentrations and the activity of matrix metalloproteinase-8 (MMP-8) and MMP-9.

Results: Atheromatous plaques (> 40% fat) were less frequently observed in women than in men (22 versus 40%; p < 0.001). In addition, more women than men had a low macrophage staining (18 versus 11%; p = 0.05) and strong smooth muscle cell staining (38 versus 24%; p = 0.001). Compared with men, women had a lower plaque concentration of IL-8 and lower MMP-8 activity. The observed differences were most pronounced in the asymptomatic group. An atheromatous plaque occurred in 9% of asymptomatic women compared to 39% ofasymptomatic men (p = 0.02). Moreover, a large proportion of plaques obtained from asymptomatic women showed high smooth muscle cell content (53 versus 30%; p = 0.03) and high collagen content (55 versus 24%; p = 0.003). All relations between gender and plaque characteristics, except for MMP-8, remained the same in a multivariate analysis that was adjusted for clinical presentation and other cardiovascular risk factors.

Conclusion: Women with a carotid stenosis had more stable plaques than men, independent of clinical presentation and cardiovascular risk profile. Asymptomatic women demonstrated the highest prevalence of stable plaques. These findings may explain why women benefit less from carotid endarterectomy than men.