Mechanical Characterization of Thrombi Retrieved With Endovascular Thrombectomy in Patients With Acute Ischemic Stroke

Abstract

Background and Purpose: Mechanical properties of thromboemboli play an important role in the efficacy of endovascular thrombectomy (EVT) for acute ischemic stroke. However, very limited data on mechanical properties of human stroke thrombi are available. We aimed to mechanically characterize thrombi retrieved with EVT, and to assess the relationship between thrombus composition and thrombus stiffness. Methods: Forty-one thrombi from 19 patients with acute stroke who underwent EVT between July and October 2019 were mechanically analyzed, directly after EVT. We performed unconfined compression experiments and determined tangent modulus at 75% strain (E t75 ) as a measure for thrombus stiffness. Thrombi were histologically analyzed for fibrin/platelets, erythrocytes, leukocytes, and platelets, and we assessed the relationship between histological components and E t75 with univariable and multivariable linear mixed regression. Results: Median E t75 was 560 (interquartile range, 393–1161) kPa. In the multivariable analysis, fibrin/platelets were associated with increased E t75 (aβ, 9 [95% CI, 5 to 13]) kPa, erythrocytes were associated with decreased E t75% (aβ, −9 [95% CI, −5 to −13]) kPa. We found no association between leukocytes and E t75 . High platelet values were strongly associated with increased E t75 (aβ, 56 [95% CI, 38–73]). Conclusions: Fibrin/platelet content of thrombi retrieved with EVT for acute ischemic stroke is strongly associated with increased thrombus stiffness. For thrombi with high platelet values, there was a very strong relationship with thrombus stiffness. Our data provide a basis for future research on the development of next-generation EVT devices tailored to thrombus composition.

Multimodality Characterization of the Clot in Acute Stroke

“…However, studying the effect of antithrombotic medication onto the thrombus composition can encounter several limitations, and must be cautiously interpreted even when larger sample sizes are studied (41). Polyhedrocites, often found in core regions of red clots, are recognized as markers of intravital contraction (42)(43)(44), and potential contributors to stiffness (45). Polyhedrocites were previously found to be the prevailing cell type in red clots, and can be related with clinical features such as stroke severity (44).…”

A high resolution scanning electron microscopy analysis of intracranial thrombi embedded along the stent retrievers

“…Knowledge about the deformability and friction properties of main components of thrombi, red blood cells 11 and fibrin 12 , 13 , enables scientists to design parametric studies in vascular phantoms and to anticipate the effectiveness of various thrombectomy techniques 14 , 15 . Nevertheless, compared to thrombi artificially generated in vitro, thrombi retrieved from patients are inherently more complex and diverse in terms of composition, morphology and mechanical properties 16 , 17 . A recent study, focused on mechanical properties of human stroke thrombi retrieved with endovascular techniques, reports that thrombi with increased fibrin/platelet content display an increase in stiffness, compared with thrombi rich in red blood cells 17 .…”

“…Nevertheless, compared to thrombi artificially generated in vitro, thrombi retrieved from patients are inherently more complex and diverse in terms of composition, morphology and mechanical properties 16 , 17 . A recent study, focused on mechanical properties of human stroke thrombi retrieved with endovascular techniques, reports that thrombi with increased fibrin/platelet content display an increase in stiffness, compared with thrombi rich in red blood cells 17 . The latter are also known to be more vulnerable to extraction with MTB 18 .…”

Fibrin to von Willebrand factor ratio in arterial thrombi is associated with plasma levels of inflammatory biomarkers and local abundance of extracellular DNA

“…The composition of these thrombi determines their structure, mechanical stability, susceptibility to lysis, and consequently, the clinical outcome [3]. Thus, fibrin content of thrombi retrieved with endovascular thrombectomy in AIS shows association with increased thrombus stiffness, whereas their red blood cell (RBC) content with decreased thrombus stiffness [4]. Consequently, the fibrin-rich thrombi are retrieved with higher number of passes in mechanical thrombectomy [5].…”