Clot Composition Research Articles

Optimizing Tigertriever adjustable stentriever technique: Operators' experience.

The Tigertriever is a novel, radially adjustable stentriever that addresses limitations in traditional mechanical thrombectomy devices by providing enhanced user control over clot integration. This provides the ability to adapt to patient-specific factors such as varying vessel sizes and clot compositions and may be particularly crucial for ensuring efficacy and safety in distal locations. This consensus paper synthesizes the clinical techniques from a consortium of experienced international operators. It outlines the current data on the Tigertriever, discusses the new operator-controlled capabilities, and provides a recommended approach for both proximal and distal mechanical thrombectomy, emphasizing the "FLEX" approach (Fast Controlled Expansion with Relaxation) for optimal integration and reduced clot disruption.

A hyper-viscoelastic uniaxial characterization of collagenous embolus analogs in acute ischemic stroke

PurposeAcute ischemic stroke is a leading cause of death and morbidity worldwide. Despite advances in medical technology, nearly 30% of strokes result in incomplete vessel recanalization. Recent studies have demonstrated that clot composition correlates with success rates of mechanical thrombectomy procedures. To understand clot behavior during thrombectomy, which exerts considerable strains on thrombi, in vitro studies must characterize the rate-dependent high-strain behavior of embolus analogs (EAs) with different formation conditions, which can be used to fit models of hyper-viscoelasticity. MethodsIn this study, the effect of collagen infiltration as a carotid-induced collagen-rich thrombosis surrogate is considered as a contributor to embolus analog high-strain stiffness, when compared to 40% hematocrit EAs. ResultsEA high-strain stiffnesses, characterized on a uniaxial load frame, increase by an order of magnitude for collagenous clot analogs. Chandler loop analogs show high-strain stiffnesses and clot compositions commensurate with previous reports of stroke patient clots, and collagenous clots show significant increase in stiffness when compared to stroke patient clots. Finally, hyper-viscoelastic curve fitting demonstrates the asymmetry between tension and compression. Nonlinear, rate-dependent models that consider clot-stiffening behavior match the high strain stiffness of clots fairly well. Furthermore, we demonstrate that the stability of the elastic energy needs to be considered to obtain optimal curve fits for high-strain, rate dependent data. ConclusionThis study provides a framework for the development of dynamically formed EAs that mimic the mechanical and structural properties of in vivo clots and provides parameters for numerical simulation of clot behavior with hyper-viscoelastic models.

Trauma patients have reduced ex vivo flow-dependent platelet hemostatic capacity in a microfluidic model of vessel injury.

Trauma is the leading cause of death in individuals up to 45 years of age. Alterations in platelet function are a critical component of trauma-induced coagulopathy (TIC), yet these changes and the potential resulting dysfunction is incompletely understood. The lack of clinical assays available to explore platelet function in this patient population has hindered detailed understanding of the role of platelets in TIC. The objective of this study was to assess trauma patient ex vivo flow-dependent platelet hemostatic capacity in a microfluidic model. We hypothesized that trauma patients would have flow-regime dependent alterations in platelet function. Blood was collected from trauma patients with level I activations (N = 34) within 60 min of hospital arrival, as well as healthy volunteer controls (N = 10). Samples were perfused through a microfluidic model of injury at venous and arterial shear rates, and a subset of experiments were performed after incubation with fluorescent anti-CD41 to quantify platelets. Complete blood counts were performed as well as plasma-based assays to quantify coagulation times, fibrinogen, and von Willebrand factor (VWF). Exploratory correlation analyses were employed to identify relationships with microfluidic hemostatic parameters. Trauma patients had increased microfluidic bleeding times compared to healthy controls. While trauma patient samples were able to deposit a substantial amount of clot in the model injury site, the platelet contribution to microfluidic hemostasis was attenuated. Trauma patients had largely normal hematology and plasma-based coagulation times, yet had elevated D-Dimer and VWF. Venous microfluidic bleeding time negatively correlated with VWF, D-Dimer, and mean platelet volume (MPV), while arterial microfluidic bleeding time positively correlated with oxygenation. Arterial clot growth rate negatively correlated with red cell count, and positively with mean corpuscular volume (MCV). We observed changes in clot composition in trauma patient samples reflected by significantly diminished platelet contribution, which resulted in reduced hemostatic function in a microfluidic model of vessel injury. We observed a reduction in platelet clot contribution under both venous and arterial flow ex vivo in trauma patient samples. While our population was heterogenous and had relatively mild injury severity, microfluidic hemostatic parameters correlated with different patient-specific data depending on the flow setting, indicating potentially differential mechanistic pathways contributing to platelet hemostatic capacity in the context of TIC. These data were generated with the goal of identifying key features of platelet dysfunction in bleeding trauma patients under conditions of flow and to determine if these features correlate with clinically available metrics, thus providing preliminary surrogate markers of physiological platelet dysfunction to be further studied across larger cohorts. Future studies will continue to explore those relationships and further define mechanisms of TIC and their relationship with patient outcomes.

Dynamic Perviousness Has Predictive Value for Clot Fibrin Content in Acute Ischemic Stroke.

Dynamic perviousness is a novel imaging biomarker, with clot density measurements at multiple timepoints to allow longer contrast to thrombus interaction. We investigated the correlations between dynamic perviousness and clot composition in the setting of acute ischemic stroke. Thirty-nine patients with large vessel occlusion (LVO) undergoing mechanical thrombectomy (MT) were analyzed. Patients received a three-phase CT imaging pre-thrombectomy and histopathological analysis of retrieved clots. Clot densities for every phase and change in densities between phases were calculated, leading to four patterns of dynamic perviousness: no contrast uptake, early contrast uptake with and without washout and late uptake. Clots were categorized into three groups based on dominant histologic composition: red blood cell (RBC)-rich, fibrin/platelet-rich and mixed. Clot composition was correlated with dynamic perviousness using the Kruskal-Wallis test and Pearson's correlation analysis. The dynamic perviousness categories showed a significant difference between fibrin-rich clots when compared to RBC-rich plus mixed groups. The uptake without washout category had significantly fewer fibrin clots compared to the uptake with washout (p = 0.036), and nearly significantly fewer fibrin clots when compared to the no uptake category (p = 0.057). Contrast uptake with different patterns of contrast washout showed significant differences of the likelihood for fibrin-rich clots.

Computer based visualization of clot structures in extracorporeal membrane oxygenation and histological clot investigations for understanding thrombosis in membrane lungs.

Extracorporeal membrane oxygenation (ECMO) was established as a treatment for severe cardiac or respiratory disease. Intra-device clot formation is a common risk. This is based on complex coagulation phenomena which are not yet sufficiently understood. The objective was the development and validation of a methodology to capture the key properties of clots deposed in membrane lungs (MLs), such as clot size, distribution, burden, and composition. One end-of-therapy PLS ML was examined. Clot detection was performed using multidetector computed tomography (MDCT), microcomputed tomography (μCT), and photography of fiber mats (fiber mat imaging, FMI). Histological staining was conducted for von Willebrand factor (vWF), platelets (CD42b, CD62P), fibrin, and nucleated cells (4', 6-diamidino-2-phenylindole, DAPI). The three imaging methods showed similar clot distribution inside the ML. Independent of the imaging method, clot loading was detected predominantly in the inlet chamber of the ML. The μCT had the highest accuracy. However, it was more expensive and time consuming than MDCT or FMI. The MDCT detected the clots with low scanning time. Due to its lower resolution, it only showed clotted areas but not the exact shape of clot structures. FMI represented the simplest variant, requiring little effort and resources. FMI allowed clot localization and calculation of clot volume. Histological evaluation indicated omnipresent immunological deposits throughout the ML. Visually clot-free areas were covered with leukocytes and platelets forming platelet-leukocyte aggregates (PLAs). Cells were embedded in vWF cobwebs, while vWF fibers were negligible. In conclusion, the presented methodology allowed adequate clot identification and histological classification of possible thrombosis markers such as PLAs.

Atrial fibrillation is associated with higher first pass effect following thrombectomy for large vessel occlusion

BackgroundFirst pass effect (FPE), defined as single-pass complete or near complete reperfusion during endovascular thrombectomy (EVT) for large vessel occlusion (LVO) strokes, is a critical performance metric. Atrial fibrillation (AF)-related...

Water content for clot composition prediction in acute ischemic stroke.

Mechanical thrombectomy (MT) has become the gold standard care for treating acute ischemic stroke (AIS) due to large vessel occlusion. Emerging evidence suggests that understanding the composition of clots prior to intervention could be useful for the selection of neuroendovascular techniques, potentially improving the efficacy of treatments. However, current imaging modalities lack the ability to distinguish clot composition accurately and reliably. Since water content can influence signal intensity on CT and MRI scans, its assessment may provide indirect clues about clot composition. This study aimed to elucidate the correlation between water content and clot composition using human clots retrieved from stroke patients and experimentally generated ovine clots. This study involved an analysis of ten clots retrieved from patients with AIS undergoing MT. Additionally, we created ten red blood cells (RBC)-rich and ten fibrin-rich ovine blood clots, which were placed in a human intracranial vascular model under realistic flow conditions. The water content and compositions of these clots were evaluated, and linear regression analyses were performed to determine the relationship between clot composition and water content. The regression analysis in human stroke clots revealed a significant negative association between RBC concentration and water content. We also observed a positive correlation between water content and both fibrin and platelets in ovine blood clots. Conclusion.

How Clot Composition Influences Fibrinolysis in the Acute Phase of Stroke: A Proteomic Study of Cerebral Thrombi.

The dramatic clinical improvement offered by mechanical thrombectomy raised questions about the relevance of prior intravenous thrombolysis in large-vessel occlusion strokes. Hence, studying intravenous thrombolysis susceptibility and its dependence on thrombus composition is crucial. We used an observational proteomic study of whole thrombi retrieved by mechanical thrombectomy to identify factors associated with fibrin content and fibrinolytic activity (FA). In 104 stroke patients, the thrombi proteome was established by mass spectrometry coupled to liquid chromatography. FA was estimated in clots both outside (FAout) by measuring D-dimer levels at the blood-thrombus interface and inside (FAin) by evaluating the ratio of fibrinogen α to its plasmin-cleaved forms using proteomics coupled with protein electrophoresis. The factors associated with fibrin content, FAin, and FAout were determined by intravenous thrombolysis-adjusted linear regression. FAout (P<0.0001) and FAin (P=0.0147) were driven by recombinant tissue-type plasminogen activator (r-tPA) administration (47/104) and thrombus composition. Indeed, FAout was greater with fibrin-rich than erythrocyte-rich thrombi, presumably because of more (r)tPA substrates. Thus, FAout was increased with cardioembolic thrombi (72/104), which are rich in fibrin (P=0.0300). Opposite results were found inside the thrombus, suggesting that (r)tPA penetrability was hampered by the density of the fibrinous cap. Moreover, blood cells had a strong impact on thrombus structure and susceptibility to (r)tPA. Indeed, fibrin content was negatively associated with erythrocyte-specific proteins in the thrombus, admission hematocrit (P=0.0139), and hemoglobin level (P=0.0080), which underlines the key role of erythrocytes in thrombus composition. Also, an increased number of neutrophils impaired FAout (P=0.0225), which suggests that their aggregation around the thrombus prevented the (r)tPA attack. Only FAout was significantly associated with reduced thrombus weight (P=0.0310), increased recanalization rate (P=0.0150), good clinical outcome (P=0.0480), and reduced mortality (P=0.0080). Proteomics can offer new insights into the close relationship between thrombus composition and susceptibility to fibrinolysis, paving the way for new adjuvant therapies.

Decoding Molecular Mechanisms Underlying Outcomes After Ischemic Stroke Thrombectomy by RNA Sequencing of Retrieved Clots.

Transcriptomic profiling has emerged as a powerful tool for exploring the molecular landscape of ischemic stroke clots and providing insights into the pathophysiological mechanisms underlying stroke progression and recovery. In this study, we aimed to investigate the relationship between stroke clot transcriptomes and stroke thrombectomy outcome, as measured by early neurological improvement (ENI) 30 (i.e., a 30% reduction in NIHSS at 24 h post-thrombectomy). We hypothesized that there exist distinct clot gene expression patterns between good and poor neurological outcomes. Transcriptomic analysis of 32 stroke clots retrieved by mechanical thrombectomy was conducted. Transcriptome data of these clots were analyzed to identify differentially expressed genes (DEGs), defined as those with a log(fold-change) ≥ 1.5 and q < 0.05 between samples with good and poor early neurological outcomes. Gene ontology and bioinformatics analyses were performed on genes with p < 0.01 to identify enriched biological processes and Ingenuity Pathway Analysis canonical pathways. Moreover, AUC analysis assessed the predictive power of DEGs for 90-day function outcome (mRS ≤ 2) and cellular composition of clot was predicted using CIBERSORT. We also assessed whether differential enrichment of immune cell types could indicate patient survival. A total of 41 DEGs were identified. Bioinformatics showed that enriched biological processes and pathways emphasized the chronic immune response and matrix metalloproteinase inhibition. Moreover, 25 of the DEGs were found to be significant predictors of 90-day mRS. These genes were indicative of monocytes enrichment and neutrophil depletion in patients with poorer outcomes. Our study revealed a distinct gene expression pattern and dysregulated biological pathways associated with ENI. This expression pattern was also predictive of long-term outcome, suggesting a biological link between those ENIs and 90-day mRS.

Aging of deep venous thrombosis in-vivo using polarization sensitive optical coherence tomography.

Deep venous thrombosis (DVT) is a medical condition with significant post-event morbidity and mortality coupled with limited treatment options. Treatment strategy and efficacy are highly dependent on the structural composition of the thrombus, which evolves over time from initial formation and is currently unevaluable with standard clinical testing. Here, we investigate the use of intravascular polarization-sensitive optical coherence tomography (PS-OCT) to assess thrombus morphology and composition in a rat DVT model in-vivo, including changes that occur over the thrombus aging process. PS-OCT measures tissue birefringence, which provides contrast for collagen and smooth muscle cells that are present in older, chronic clots. Thrombi in the inferior vena cava of two cohorts of rats were imaged in-vivo with intravascular PS-OCT at 24 hours (acute, nrats = 3, 73 cross-sections) or 28 days (chronic, nrats = 4, 41 cross-sections) after thrombus formation. Co-registered histology was labelled by an independent pathologist to establish ground-truth clot composition. Automated analysis of OCT cross-sectional images differentiated acute and chronic thrombi with 97.6% sensitivity and 98.6% specificity using a linear discriminant model comprised of both polarization and conventional OCT metrics. These results support PS-OCT as a highly sensitive imaging modality for the assessment of DVT composition to differentiate acute and chronic thrombi. Intravascular PS-OCT imaging could be integrated with advanced catheter-based treatment strategies and serve to guide therapeutic decision-making and deployment, by offering an accurate assessment of DVT patients in real time.

Abstract 1069: Novel Approaches Dissecting Human Thrombus Composition

Introduction: Thrombus formation is a key contributor to ischemic stroke and cardiovascular diseases. Variations in thrombus composition involving platelets, fibrin, and leukocytes play a pivotal role in the pathophysiology, impacting clinical outcomes. Understanding its character and the interplay with Neutrophil Extracellular Traps (NETs) is clinically vital due to treatment response and outcome. This study introduces light-sheet microscopy and holotomography to dissect clot composition, aiming to enhance clinical insights into thrombosis. Unraveling these complexities holds promise for targeted interventions and improved patient outcomes. Aims: This study aimed to enhance our understanding of human blood thrombus composition by employing a novel approach using light-sheet microscopy and holotomography. Methods: Human thrombus samples were obtained by mechanical thrombectomy from acute ischemic stroke patients. To access the thrombus structure, the samples were cleared by a tissue-clearing rapid system, and light-sheet microscope imaging was obtained with CitH3, CD45, P-selectin, and fibrin. Holotomography images were obtained from cryosectioned thrombus at 5μm thickness and stained with DAPI and CitH3. Holotomography provided quantitative information on the refractive index of thrombus components. Comparative analysis with traditional imaging methods was performed to assess the advantages of the novel approaches. Results: The results revealed a comprehensive visualization of the spatial arrangement of human thrombus composition through light-sheet microscopy imaging. Holotomography successfully acquired a three-dimensional image of a thrombus section sample. HT images were used to qualitatively distinguish differences in neutrophil RI distribution by NETosis and differences in RI values within the immune cell population. Conclusion: This study demonstrates the efficacy of combining light sheet microscopy and holotomography to comprehensively dissect human thrombus composition. The integration of these advanced imaging techniques provides an understanding of thrombosis, surpassing the limitations of traditional methods.

Clot composition and recanalization outcomes in mechanical thrombectomy

BackgroundMechanical thrombectomy (MT) has become standard for large vessel occlusions, but rates of complete recanalization are suboptimal. Previous reports correlated radiographic signs with clot composition and a better response to...

Multimaterial decomposition in dual-energy CT for characterization of clots from acute ischemic stroke patients

BackgroundNowadays, there is no method to quantitatively characterize the material composition of acute ischemic stroke thrombi prior to intervention, but dual-energy CT (DE-CT) offers imaging-based multimaterial decomposition. We retrospectively investigated the material composition of thrombi ex vivo using DE-CT with histological analysis as a reference.MethodsClots of 70 patients with acute ischemic stroke were extracted by mechanical thrombectomy and scanned ex vivo in formalin-filled tubes with DE-CT. Multimaterial decomposition in the three components, i.e., red blood cells (RBC), white blood cells (WBC), and fibrin/platelets (F/P), was performed and compared to histology (hematoxylin/eosin staining) as reference. Attenuation and effective Z values were assessed, and histological composition was compared to stroke etiology according to the Trial of ORG 10172 in Acute Stroke Treatment (TOAST) criteria.ResultsHistological and imaging analysis showed the following correlation coefficients for RBC (r = 0.527, p < 0.001), WBC (r = 0.305, p = 0.020), and F/P (r = 0.525, p < 0.001). RBC-rich thrombi presented higher clot attenuation in Hounsfield units than F/P-rich thrombi (51 HU versus 42 HU, p < 0.01). In histological analysis, cardioembolic clots showed less RBC (40% versus 56%, p = 0.053) and more F/P (53% versus 36%, p = 0.024), similar to cryptogenic clots containing less RBC (34% versus 56%, p = 0.006) and more F/P (58% versus 36%, p = 0.003) than non-cardioembolic strokes. No difference was assessed for the mean WBC portions in all TOAST groups.ConclusionsDE-CT has the potential to quantitatively characterize the material composition of ischemic stroke thrombi.Relevance statementUsing DE-CT, the composition of ischemic stroke thrombi can be determined. Knowledge of histological composition prior to intervention offers the opportunity to define personalized treatment strategies for each patient to accomplish faster recanalization and better clinical outcomes.Key points• Acute ischemic stroke clots present different recanalization success according to histological composition.• Currently, no method can determine clot composition prior to intervention.• DE-CT allows quantitative material decomposition of thrombi ex vivo in red blood cells, white blood cells, and fibrin/platelets.• Histological clot composition differs between stroke etiology.• Insights into the histological composition in situ offer personalized treatment strategies.Graphical

316 Acute Ischemic Stroke Presentation Labs and Imaging Can Be Used to Model Thrombus Proteomic Composition

INTRODUCTION: The literature points to a strong relationship between the composition of acute ischemic stroke thrombi and their susceptibility to thrombolytic or endovascular treatment. Composition can be determined by molecular studies of the clot itself, but there is tremendous utility in being able to predict clot composition solely on data available at patient presentation. METHODS: Quantitative proteomes were generated using mass spectrometry of thromboembolic material retrieved by thrombectomy from 59 stroke patients. Of the 2,790 total identified proteins, marker proteins were selected to identify broad groups of thrombus components: RBCs (12 proteins), platelets (9 proteins), histones (23 proteins) and neutrophils (13 proteins). Dimensional reduction of marker proteins was done by principal component (PC) analysis for each group. A broad survey of demographic, lab, and radiographic data was gathered by retrospective chart review. Regression analysis was used to identify the combination of the four variables on chart review that most strongly associated with the PCs for each thrombus component group. RESULTS: After dimensional reduction, a significant amount of the variance in marker protein abundance for each group was represented by the first PC for each group (R2 &gt; 0.94 for all). It was possible to generate linear models representing the PC associated with RBCs (R2 = 0.37, p = 0.02), platelets (R2 = 0.40, p = 0.0004), histones (R2 = 0.52 and p = 0.001), and neutrophils (R2 = 0.81, p = 1E-12) using combinations of four data points at presentation. CONCLUSIONS: This preliminary work suggests that the abundance of clot components may be predicted by modeling patient data available at presentation, which has the potential to drive future choice of therapy. Next steps include refining and validating the models on a prospectively maintained stroke database at our home institution.

Electrical impedance measurements can identify red blood cell–rich content in acute ischemic stroke clots ex vivo associated with first-pass successful recanalization

BackgroundElectrochemical impedance spectroscopy can determine characteristics such as cell density, size, and shape. The development of an electrical impedance–based medical device to estimate acute ischemic stroke (AIS) clot characteristics could improve stroke patient outcomes by informing clinical decision making. ObjectivesTo assess how well electrical impedance combined with machine learning identified red blood cell (RBC)–rich composition of AIS clots ex vivo, which is associated with a successfully modified first-pass effect. MethodsA total of 253 clots from 231 patients who underwent thrombectomy in 5 hospitals in France, Japan, Serbia, and Spain between February 2021 and October 2023 were analyzed in the Clotbase International Registry. Electrical impedance measurements were taken following clot retrieval by thrombectomy, followed by Martius Scarlet Blue staining. The clot components were quantified via Orbit Image Analysis, and RBC percentages were correlated with the RBC estimations made by the electrical impedance machine learning model. ResultsQuantification by Martius Scarlet Blue staining identified RBCs as the major component in clots (RBCs, 37.6%; white blood cells, 5.7%; fibrin, 25.5%; platelets/other, 30.3%; and collagen, 1%). The impedance-based RBC estimation correlated well with the RBC content determined by histology, with a slope of 0.9 and Spearman’s correlation of r = 0.7. Clots removed in 1 pass were significantly richer in RBCs and clots with successful recanalization in 1 pass (modified first-pass effect) were richer in RBCs as assessed using histology and impedance signature. ConclusionElectrical impedance estimations of RBC content in AIS clots are consistent with histologic findings and may have potential for clinically relevant parameters.

Development of a super-hydrophilic anaerobic tube for the optimization of platelet-rich fibrin

Horizontal platelet-rich fibrin (H-PRF) contains a variety of bioactive growth factors and cytokines that play a key role in the process of tissue healing and regeneration. The blood collection tubes used to produce Solid-PRF (plasmatrix (PM) tubes) have previously been shown to have a great impact on the morphology, strength and composition of the final H-PRF clot. Therefore, modification to PM tubes is an important step toward the future optimization of PRF. To this end, we innovatively modified the inner wall surface of the PM tubes with plasma and adjusted the gas environment inside the PM tubes to prepare super-hydrophilic anaerobic plasmatrix tubes (SHAP tubes). It was made anaerobic for the preparation of H-PRF with the aim of improving mechanical strength and bioactivity. The findings demonstrated that an anaerobic environment stimulated platelet activation within the PRF tubes. After compression, the prepared H-PRF membrane formed a fibrous cross-linked network with high fracture strength, ideal degradation characteristics, in addition to a significant increase in size. Thereafter, the H-PRF membranes prepared by the SHAP tubes significantly promoted collagen synthesis of gingival fibroblast and the mineralization of osteoblasts while maintaining excellent biocompatibility, and advantageous antibacterial properties. In conclusion, the newly modified PRF tubes had better platelet activation properties leading to better mechanical strength, a longer degradation period, and better regenerative properties in oral cell types including gingival fibroblast and alveolar osteoblasts. It also improves the success rate of H-PRF preparation in patients with coagulation dysfunction and expands the clinical application scenario.

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 &lt;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&lt;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 &lt;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.

Abstract TMP87: Thrombus Age in Ischemic Stroke With Atrial Fibrillation

Background and purpose: Because the biochemical composition of thrombus changes after formation over time, thrombus maturation in the left atrium may affect clot compositions in ischemic stroke with atrial fibrillation (AF). We aimed to investigate the association of the age of retrieved thrombi with clinical features and outcomes after MT for ischemic stroke with AF. Methods: We retrospectively reviewed consecutive patients with ischemic stroke with known AF or AF diagnosed after stroke onset who underwent MT and whose retrieved thrombi were pathologically analyzed. Thrombi were classified as fresh (&lt;1 day) and older (1-5 days) based on the areas (≤20 % or &gt;20 %) of lytic features of granulocytes in the section. Components of thrombi were quantified using immunostaining. Outcomes included first pass effect (FPE, extended Thrombolysis in Cerebral Infarction [eTICI] 2c/3 after first pass) and favorable outcome (3-month modified Rankin Scale score of 0 to 2 or equal to premorbid mRS score). Results: Of 168 patients, 62 patients (37%) had older thrombi. The presence of older thrombi was independently associated with the higher CHADS 2 score (adjusted OR [aOR], 1.46; 95% confidence interval [CI], 1.07-1.99). Older thrombi had the higher proportion of fibrin, platelets, von Willebrand factor, and neutrophil extracellular traps than fresh thrombi. FPE was less frequently achieved in patients with older thrombi than those with fresh thrombi (21% versus 43%; aOR, 0.36; 95% CI, 0.17-0.77). Favorable outcomes were fewer in patients with older thrombi than those with fresh thrombi (40% versus 73%; aOR, 0.37; 95% CI, 0.16-0.85). Conclusions: In patients with ischemic stroke with AF, older thrombi was associated with cardiovascular risk factors and included abundant amounts of components associated with the thrombectomy resistance. Patients with older thrombi had poorer functional outcomes presumably due to concomitant risk factors and worse revascularization outcomes.

MicroCT and Histological Analysis of Clot Composition in Acute Ischemic Stroke : AComparative Study of MT-Retrieved Clots and Clot Analogs.

Assessing clot composition on prethrombectomy computed tomography (CT) imaging may help in stroke treatment planning. In this study we seek to use microCT imaging of fabricated blood clots to understand the relationship between CT radiographic signals and the biological makeup. Clots (n = 10) retrieved by mechanical thrombectomy (MT) were collected, and 6clot analogs of varying RBC composition were made. We performed paired microCT and histological image analysis of all 16clots using aScanCo microCT 100 (4.9 µm resolution) and standard H&E staining (imaged at 40×). From these data types, first order statistic (FOS) radiomics were computed from microCT, and percent composition of RBCs (%RBC) was computed from histology. Polynomial and linear regression (LR) were used to build statistical models based on retrieved thrombus microCT and %RBC that were evaluated for their ability to predict the %RBC of clot analogs from mean HU. Correlation analyses of microCT FOS with composition were completed for both retrieved clots and analogs. The LR model fits relating MT-retrieved clot %RBC with mean (R2 = 0.625, p = 0.006) and standard deviation (R2 = 0.564, p < 0.05) in HUs on microCT were significant. Similarly, LR models relating analog histological %RBC to analog protocol %RBC (R2 = 0.915, p = 0.003) and mean HUs on microCT (R2 = 0.872, p = 0.007) were also significant. When the LR model built using MT-retrieved clots was used to predict analog %RBC from mean HUs, significant correlation was observed between predictions and actual histological %RBC (R2 = 0.852, p = 0.009). For retrieved clots, significant correlations were observed for energy and total energy with %RBC and %FP (|R| > 0.7, q < 0.01). Analogs further demonstrated significant correlation between FOS energy, total energy, variance and %WBC (|R| > 0.9, q < 0.01). MicroCT can be used to build models that predict AIS clot composition from routine CT parameters and help us to better understand radiomic signatures associated with clot composition and first pass outcomes. In future work, such observations can be used to better infer clot composition and inform thrombectomy prognostics from pretreatment CTs.

Multimodality Quantification of Thrombus Deposition in Extracorporeal Membrane Oxygenation (ECMO); Correlating Oxygenator Computed Tomography Imaging, Electron Microscopy and Histology to Clinical Outcomes

Introduction: Extracorporeal membrane oxygenation (ECMO) is essential for supporting cardiopulmonary function in critically ill patients, However, ECMO incurs thrombogenic risks due to activation of coagulation factors and blood cells by the biomaterial surfaces. This leads to complications such as frequent device replacement and systemic embolization despite the use of anticoagulation, suggesting additional mechanisms contribute to medical device-associated thrombosis. We propose that the geometry of the ECMO oxygenator significantly influences the structure and extent of clot formation and stability. To investigate this, we employed quantitative imaging and histologic techniques for a high-resolution, three-dimensional analysis of clot morphology in ECMO components, aiming to enhance our understanding of clot formation mechanisms, correlate these observations to clinical outcomes, and develop effective mitigation strategies. Methods: We developed a prospective study in which patients consented to the collection of blood samples, used ECMO components, and collection of relevant clinical variables. Computed tomography (CT) images were acquired using an Inveon microCT. H&amp;E stains, scanning electron microscopy (SEM), and CT images were processed through the Dragonfly software to accomplish a 3D visualization and analysis of clot composition. Clinical demographics and ECMO characteristics were recorded for each patient. Results: Digital photographs of used oxygenators are displayed in figure (A). Through CT scans, we quantified clot formation of distinct densities across the layers of the ECMO oxygenator (D). The results were able to quantify intraoxygenator thrombosis with high fidelity (27.65%, 14.56%, and 26.35% of the available membrane area was thrombosed across three representative oxygenators). Using a frontal CT scan to investigate clot formation identified five layers of varying structures across the intended path of blood flow (B). Clot formation was observed in layer 4 and layer 5, in which thrombosis occluded up to 12.2% of the layer on average. The overall ranking of clot formation under hemodynamic performance changes for all five layers was as follows: layer 5 &amp;gt; layer 4 &amp;gt; layer 1 = layer 2 &amp;gt;&amp;gt; layer 3. The use of anticoagulation at the time of ECMO decannulation significantly reduced the content of clot formation (P&amp;lt;0.0001). We then correlated digital biomarkers from imaging with thrombus composition. Detailed histological examination (HE) and SEM was undertaken on dismantled oxygenators (B &amp; C). We focused on thrombi at the interfaces and within the hollow fibers of the oxygenator. SEM and HE staining illustrated increased thickness, length, and density of fibrin structures in the thrombi from layer 5 to layer 4, whereas the numbers of platelets and cells decreased. Overall, layer 5 exhibited the most diverse types of thrombi, including blood cell-rich, platelet-rich, and fibrin-rich clots. We also observed aligned clots and significant clot formation in the hollow fiber area of layer 4, reflecting the geometry of the specific layer. Discussion: This pilot study examined the potential for imaging-based modalities to evaluate device associated thrombosis ex vivo, correlating these imaging findings to direct observations of thrombus composition and location. This methodology provides a platform to investigate ECMO device failure, identifying the key locations within select oxygenators where local device modification may be of most benefit. Future research will prioritize designing membrane oxygenator properties to minimize thrombus deposition, and will allow us to incorporate the use of serial imaging endpoints in future clinical trials evaluating medical device-associated thrombosis.