Abstract WP302: Different Clot Characteristics According to the Clot Volume: A Microscopic Analysis of Clot Composition

Background and Objectives: Understanding the mechanisms of thrombosis is crucial for the future advancement in treating ischemic stroke. While many researches on thrombogenesis have been conducted, there was a limited data on thrombus growth. In this study, we investigated whether the clot composition or clot characteristics differed by the clot size using microscopic analysis of ischemic clot. Methods: We obtained the clots from 238 ischemic stroke patients who received endovascular treatment between July 2017 and July 2023 at Severance Stroke Center. We quantitatively analysed the clot components identified using immunohistochemistry. The fractions of each component such as fibrin, red blood cells (RBC), and platelets were calculated as the percentage pixel density of the total clot area. Clot volume was semiautomatically measured on thin-section computed tomography performed at stroke presentation using software. We determined the association between clot volume and histopathologic composition, arrangement patterns, and clinical or radiological features. Results: Among the 238 patients, the median (interquartile) of clot volume was 47.0 mm 3 (range 23.8-79.8). As the clot volume increased, the proportion of RBC became larger (r = 0.307. P <0.001) and the proportion of platelet became smaller (r = -0.150, p=0.029). In terms of RBC patterns, purely aggregated RBC patterns, rather than RBC-fibrin mixture patterns, was positively associated with the clot volume. After adjusting for potential confounders including posterior circulation occlusion, serum hemoglobin levels, serum albumin levels, and the presence of active cancer (all p<0.05 in univariable analysis), clot volume was independently related with the proportion of RBC (ß 0.726, SE 0.302, p =0.017) or the presence of purely aggregated RBC pattern (ß 59.182, SE 11.684, p <0.001). Conclusions: As the clot volume increased, the proportion of RBCs increases, and areas of purely packed with RBCs become larger. These findings suggest that as the clot grows, RBC mainly involved the clot volume growth.