Background: Ischemic stroke remains a major global health threat and a leading cause of mortality. Although advancements have been made in acute ischemic stroke treatment, challenges persist in achieving efficient recanalization and improved outcomes. Research on the mechanical characterization of ex vivo thrombi is limited. This paper aims to investigate the compositional and mechanical characterization of acute ischemic stroke thrombi retrieved in a per pass method and determine the relationship between composition and mechanical properties.
Methods: Thrombi fragments were collected per pass and segmented into samples. Larger fragments were sectioned into 1 mm pieces for cyclic unconfined compression testing, assessing hysteresis and tangent modulus as a measure of stiffness. The remaining pieces post-sectioning were combined into a single offcut sample, while smaller fragments were labeled as extra samples and kept for histology. Following mechanical testing, compositional analyses quantified the percentages of red blood cells, fibrin, and platelets in each sample.
Results: In 34 passes, a total of 108 thrombus fragments from 20 patients were successfully retrieved. Compositional heterogeneity was observed both between patients and within a single patient. Higher red blood cells (RBC) and lower fibrin/platelet contents were associated with Pass 1. The results showed a mean hysteresis area of 1.6 kPa and a mean hysteresis ratio of 37%. The median low strain stiffness was 1.76 kPa and the median high strain stiffness was 576.4 kPa. RBC and fibrin/platelets concentration had a linear relationship with high strain stiffness. Low strain stiffness, hysteresis area, and ratio changed with varying quantities of fibrin/platelets, RBC, and platelets composition.
Conclusion: This study enhances understanding of the relationship between thrombus composition and mechanical properties. The findings highlight the significant heterogeneity in thrombi and the non-linear viscoelastic behavior. Stiffness is highly corelated to strain levels, and the hysteresis amount depends on structural changes and varying compositional concentrations.