Morphological organization of thrombus after endovascular thrombus extraction in patients with ischemic heart disease

Relevance: Ischemic heart disease (IHD) claims the lives of approximately 18 million people annually. The vascular damage that occurs during this process is the primary cause of clinical manifestations, with the thrombus being one of the material substrates. Venous and atherothrombosis initiate inflammation with the participation of immune cells, cytokines, and chemokines. Therefore, understanding the molecular and cellular mechanisms of thrombosis is crucial and requires further research to address this issue. Furthermore, studying the morphological features of the removed thrombus and identifying the specific cell type that forms it will help identify potential predictors of the risk of complications during thrombosis treatment. The aim of this study was to investigate the morphological and immunohistochemical characteristics of thrombi after endovascular thrombectomy in patients with coronary artery disease.

Materials and methods: Morphological examination was performed on biopsy specimens obtained by aspiration of thrombotic masses from the occluded artery. The obtained biomaterial was fixed in 10 % buffered neutral formalin and embedded in paraffin using standard techniques. Histological sections were prepared and stained with hematoxylin and eosin, using the Picro-Mallory method, and immunohistochemistry was performed using monoclonal antibodies to CD68, CD45RA, and MPO. All obtained slides were examined under a light microscope and photographed. Morphometric analysis was performed using ImagoJ software, and statistical processing was performed using the MS Excel 2010 statistical analysis package.

Results: The quality of thrombus organization and the rate of its formation depend on the duration and severity of coronary heart disease. The observed maximum leukocyte count on the first day, primarily due to neutrophils, and the maximum surface area (61.2 %) occupied by fibrin indicate an early stage of thrombus organization. A dynamic two-fold decrease in neutrophils and a 1.5-fold increase in macrophages, accompanied by a 1.6-fold decrease in the area occupied by fibrin on day 3, indicated active thrombus resorption and tissue remodeling – an intermediate stage of thrombus organization. A 2.2-fold decrease in macrophages, accompanied by a significant 1.9-fold increase in endothelial cells and fibroblasts and minimal fibrin area (a 2.9-fold decrease compared to day 3) on day 7, indicated the formation of granulation tissue, scar tissue, vascular wall remodeling, and active angiogenesis – a late stage of thrombus organization.

Conclusions: The obtained morphological data regarding the cellular component of the thrombus complement the picture of thrombosis dynamics and can be considered when developing strategies to improve preventive and therapeutic measures for patients with coronary artery disease.