Comparison study of the quantitative and semi-quantitative analysis of pathological features of carotid atherosclerotic plaque instability Huaien Zheng1, Karina Gasbarrino1, Chi Lai2, John Veinot2, Stella S. Daskalopoulou1; 1) Research Institute of the McGill University Health Centre, Montréal, Québec; 2) Department of Pathology and Laboratory Medicine, University of Ottawa, Ontario, Canada Atherosclerosis and its thrombotic complications are a major cause of morbidity and mortality worldwide. Plaque instability and rupture is an important causative factor of these complications. To estimate plaque instability level, Lovett et al has proposed a histological classification that ranges from definitely stable to definitely unstable plaques based on semi-quantitative assessment of 10 plaque pathological features. However, semi-quantitative analysis can be subject to variability. Thus, herein, we aimed to develop a method to quantitatively measure plaque pathological features and validate it with established semi-quantitative results. Carotid surgical specimens were obtained from patients who underwent carotid endarterectomy (CEA). The atherosclerotic specimen sections were taken from the site of maximum stenosis, and stained with hematoxylin & eosin, smooth muscle cell actin, CD68 (for macrophages), and CD3 (for lymphocytes). Plaque features and stability were assessed by two vascular pathologists following Lovett’s semi-quantitative classification. Whole plaque specimen sections were scanned digitally. Pathological characteristics listed in the semi-quantitative classification were quantitatively measured using ImagePro Primer software. The quantitative image analysis results were analyzed and compared with the semi-quantitative pathological scores. The quantitative results of major pathologic features are significantly different between stable and unstable plaques and they are in accordance with the semi-quantitative analysis, performed by the pathologists. The quantitative results show that fibrous tissue occupies a major part of stable plaques (35-45%), while the lipid core occupies a large part of unstable plaques (40-47%). Furthermore, inflammatory cell infiltration is much greater in unstable plaques (P < 0.01). On the other hand, plaque calcification, neovascularization, and hemorrhage have no obvious differences between stable and unstable plaques. Our results demonstrate that quantitative image analysis can provide new insight into plaque morphology and composition: 1) the amount of fibrosis, necrotic core, fibrous cap, and inflammatory cell infiltration are major decisive factors of plaque instability; 2) Calcification and neovascularization are not closely related with plaque instability. Furthermore, quantitative image analysis of plaque features is a promising method for accurate classification of plaque instability. This new quantitative method needs to be externally validated in a larger subset of CEA plaques for future clinical practice.View Large Image Figure ViewerDownload Hi-res image Download (PPT)