The Correlation Between Collagen Types and Ultrasound Feature Score in Evaluating the Vulnerability of Carotid Artery Plaque

Objectives: To investigate whether ultrasound score has clinical value in identifying carotid artery-vulnerable plaque and the impacts of collagen distribution on the stability of plaque. Materials and Methods: Standard carotid artery ultrasound examinations were performed in 51 patients with carotid artery plaques before carotid endarterectomy. Hematoxylin-eosin staining and Sirius red–picric acid staining of plaque sections were performed to analyze the pathological features and collagen distribution. All plaques were classified into vulnerable and stable groups by pathological features. Ultrasound scores, cap thickness, and the ratios of different collagen types were recorded and analyzed between two groups and different parts of plaques. Results: Ultrasound scores of the vulnerable group were higher than those of the stable group (4.35 ± 1.23 vs. 2.09 ± 1.04, P = 0.001). AUC was 0.894 (best cutoff point three) in differentiating vulnerable and stable plaques. Compared with the stable group, the fibrous caps of the vulnerable group were thinner (P = 0.012); the area ratios of collagen type I to all collagen in the vulnerable group were lower (P = 0.033); however, the area ratios of collagen type IV to all collagen were higher (P = 0.026). Compared with downstream shoulders, the ultrasound scores of upstream shoulders of plaque were higher (P = 0.001), the fibrous caps of upstream shoulders were thinner (P = 0.001), and the area ratios of collagen type I to all collagen were lower (P = 0.022). Conclusion: Ultrasound score could have a clinical value in identifying vulnerable carotid artery plaque, and the collagen distribution could impact the stability of plaques, especially collagen type I and type IV. The results also prompted that the upstream shoulders were more vulnerable than the downstream shoulders.