Clot Composition Analysis as a Diagnostic Tool to Gain Insight into Ischemic Stroke Etiology: A Systematic Review

Procedural and Clinical Outcome of Stroke after thrombectomy according to etiology: results from a nationwide registry

BACKGROUND

The impact of stroke etiology on outcomes in patients who underwent endovascular thrombectomy (EVT) is still a matter of debate. We studied the effect of aterosclerotic versus cardioembolic etiology on the clinical and radiological outcome of patients with stroke due to large vessel occlusion (LVO) treated with EVT on a large sample of stroke patients enrolled in a nationwide registry.

METHODS

The source of data was the Italian Registry of Endovascular Stroke Treatments, a national, prospective, observational internet-based registry including patients treated with EVT since 2011. We extracted and compared data of patients suffering from large atherosclerosis (LAA) or cardioembolic (CE) stroke.

RESULTS

We included 5193 patients, 3899 CE, and 1294 LAA stroke. Patients with CE were significantly older (p < 0.001), and their stroke severity at admission was significantly higher (p < 0.001). Moreover, patients with LAA had significantly longer onset to end of procedure time, and procedure duration than CE patients. Good outcome at three months was reported in 45.2% of LAA and 45.4% of CE patients (p = 0.89). In the multivariable analysis, patients with CE had higher odds of achieving successful (OR = 1.61; 95% CI 1.35-1.92) or complete (OR = 1.40; 95% CI 1.21-1.62) recanalization Futile recanalization was detected more frequently in CE patients (OR = 1.35; 95% CI 1.18-1.61). There were no statistically significant differences in clinical outcomes (mRS 02: OR = 1.12; 95% CI 0.92-1.36). LAA patients had higher odds of sICH (OR = 0.65; 95% CI 0.49-0.85). The shift analysis showed a trend toward a better outcome in CE patients (OR = 1.19; 95% CI 0.99-1.35), which was statistically significant in subjects with anterior circulation stroke. (OR = 1.21; 95% CI 1.04-1.35).

CONCLUSIONS

The study showed a better chance of successful recanalization in CE patients, a slightly better outcome in CE patients with anterior circulation stroke after adjusting for baseline confounders, despite their more unfavourable risk factor profile, and a higher chance of futile recanalization.

Histopathological composition of thrombus material in a large cohort of patients with acute ischemic stroke: a study of atypical clots

Introduction

Clot composition appears to be associated with outcomes in stroke recanalization therapy. This study aims to analyze thrombus composition and assess the relationship between atypical clot composition and clinical parameters, laboratory markers, and recanalization strategies in a series of patients with acute ischemic stroke (AIS) undergoing endovascular treatment (EVT).

Methods

This is a prospective single-center registry conducted from December 2014 to July 2022. All retrieved clots were examined under an established protocol and classified as follows: red blood cell-rich clots (RBC), fibrin/platelet-rich clots (FPC), mixed clots (MC), septic emboli (SE), atheroma emboli (AE), fatty emboli (FE), and calcium emboli (CE). We categorized them into two groups: atypical clot composition (ACC: SE, AE, FE, and CE) and usual clot composition (UCC: RBC, FPC, and MC). A subgroup of 10 ACC (four SE, three AE, two FE, and one CE) and nine UCC (three RBC, three FPC, and three MC), matched by age and sex, was analyzed using immunohistochemistry to detect neutrophil extracellular traps (NETs).

Results

A total of 606 patients were assessed for EVT, with 448 (73.92%) meeting the inclusion criteria. The clot categorization was as follows: FPC 211 (47.1%), RBC 105 (23.4%), MC 104 (23.2%), SE 16 (3.6%), AE 5 (1.1%), CE 4 (0.9%), and FE 3 (0.7%). Consequently, we classified 420 (93.75%) patients into the UCC group and 28 (6.25%) into the ACC group. Bivariate analysis revealed that the ACC group had a significantly higher number of leukocytes (11.40 leukocytes/mm3 vs. 9.49, p = 0.005), a greater frequency of TICA occlusion (28.6% vs. 9.8%, p = 0.006), and higher mortality at three months (28.6% vs. 12.4%, p = 0.038). Multivariate analysis indicated that atypical clot composition was significantly associated with a higher prevalence of diabetes mellitus, smoking, occlusion of the terminal internal carotid artery, and an increased number of passes. Immunohistochemical studies showed the presence of neutrophil extracellular traps (NETs) in all 19 thrombi that were analyzed.

Conclusion

Diabetes and TICA occlusion were the strongest predictors of atypical clot composition. We also observed a significant association between atypical composition and an increased number of passes. Furthermore, the presence of NETs in all thrombi analyzed, regardless of their composition, indicates inflammatory mechanisms associated with clot formation and consolidation in AIS.

Proteomic Analyses of Clots Identify Stroke Etiologies in Patients Undergoing Endovascular Therapy

AIMS

This study aimed to investigate the correlation between clot composition and stroke mechanisms in patients undergoing endovascular therapy (EVT), using proteomic analysis.

METHODS

This study included 35 patients with ischemic stroke (cardioembolism [CE], n = 17; large artery atherosclerosis [LAA], n = 6; cancer-related [CR], n = 4; and undetermined (UD) cause, n = 8) who underwent EVT. Retrieved clots were proteomically analyzed to identify differentially expressed proteins associated with the three stroke mechanisms and to develop the machine learning model.

RESULTS

In the discover stage, 3838 proteins were identified using clot samples from 27 patients with CE, LAA, and CR mechanisms. Through functional enrichment and network analysis, 149 proteins were identified as potential candidates for verification studies. After verification experiments, 34 proteins were selected as the final candidates to predict stroke mechanisms. Furthermore, the machine learning-based model identified three proteins associated with each mechanism (Pleckstrin in CE; CD59 glycoprotein in LAA; and Immunoglobulin Heavy Constant Gamma 1 in CR) in the UD group.

CONCLUSIONS

This study identified specific protein markers of clots that could differentiate stroke mechanisms in patients undergoing EVT. Therefore, our results could offer valuable insights into elucidating the mechanisms of ischemic stroke, which could provide information on more effective secondary prevention strategies.

Cerebral thrombus analysis as a useful diagnostic tool for infective endocarditis in ischemic stroke patients

INTRODUCTION

Infective endocarditis (IE) is a life-threatening condition and a rare cause of ischemic stroke (IS). This study aimed to evaluate the utility of analyzing cerebral thrombi, obtained through endovascular thrombectomy in IS, for the pathological diagnosis of IE.

PATIENTS AND METHODS

Cerebral thrombi from three groups of IS patients were compared: definite IE (n = 10), cardioembolic stroke without and with concomitant infection (CE-I-: n = 30, CE-I+: n = 10). We performed histological examination, molecular biology, and microbiological tests on cerebral thrombi, to detect microorganisms and assess their composition.

RESULTS

Median age of included patients was 73 years and 50% were females. Hematoxylin & Eosin and Grocott-Gomori Methenamine Silver stains detected microorganisms in all IE cerebral thrombi, and none in the control groups. Thrombus PCR detected relevant microorganism in n = 2/7 IE. Compared to control groups, IE thrombi were characterized by significant lower content of red blood cells (median [IQR]: IE = 7.4 [4.2-26.7], CE-I- = 49.3 [17-62.6], CE-I+ = 57.5 [40.7-60.8], % over thrombus section area [%TSA], p = 0.001), increased von Willebrand Factor (IE = 23.9 [19.1-32], CE-I- = 11.2 [8.2-12.8], CE-I+ = 12.9 [10.7-18.3], %TSA, p = 0.001), cell-dominant pattern of Neutrophil Extracellular Traps (IE = 100%, CE-I- = 69%, CE-I+ = 70%, p ⩽ 0.001), and more frequent sub-acute or chronic thrombus age classification (p ⩽ 0.001). These latter thrombus features displayed good discriminative ability between IE and controls, with AUC values between 0.84 and 0.95.

DISCUSSION

Multimodal analysis of cerebral thrombi in IS with suspected IE supports early and definite pathological diagnosis by detecting pathogens and assessing changes in thrombus composition.

Inflammation biomarkers in the intracranial blood are associated with outcome in patients with ischemic stroke

BACKGROUND

Performing endovascular treatment (EVT) in patients with acute ischemic stroke (AIS) allows a port of entry for intracranial biological sampling.

OBJECTIVE

To test the hypothesis that specific immune players are molecular contributors to disease, outcome biomarkers, and potential targets for modifying AIS .

METHODS

We examined 75 subjects presenting with large vessel occlusion of the anterior circulation and undergoing EVT. Intracranial blood samples were obtained by microcatheter aspiration, as positioned for stent deployment. Peripheral blood samples were collected from the femoral artery. Plasma samples were quality controlled by electrophoresis and analyzed using a Mesoscale multiplex for targeted inflammatory and vascular factors.

RESULTS

We measured 37 protein biomarkers in our sample cohort. Through multivariate analysis, adjusted for age, intravenous thrombolysis, pretreatment National Institutes of Health Stroke Scale and Alberta Stroke Program Early CT scores, we found that post-clot blood levels of interleukin-6 (IL-6) were significantly correlated (adjusted P value <0.05) with disability assessed by the modified Rankin Scale (mRS) score at 90 days, with medium effect size. Chemokine (C-C) ligand 17 CCL17/TARC levels were inversely correlated with the mRS score. Examination of peripheral blood showed that these correlations did not reach statistical significance after correction. Intracranial biomarker IL-6 level was specifically associated with a lower likelihood of favorable outcome, defined as a mRS score of 0-2.

CONCLUSIONS

Our findings show a signature of blood inflammatory factors at the cerebrovascular occlusion site. The correlations between these acute-stage biomarkers and mRS score outcome support an avenue for add-on and localized immune modulatory strategies in AIS.

Automatic etiological classification of stroke thrombus digital photographs using a deep learning model

Background

Etiological classification of ischemic stroke is fundamental for secondary prevention, but frequently results in undetermined cause. We aimed to develop a Deep Learning (DL)-based model for automatic etiological classification of ischemic stroke using digital images of thrombi retrieved by mechanical thrombectomy.

Methods

Patients with large vessel occlusion stroke subjected to mechanical thrombectomy between April 2016 and January 2023 at La Fe University and Polytechnic Hospital in Valencia were included. Thrombus digital images were obtained and clinical characteristics, including TOAST etiological classification as reference standard, were retrieved. Statistical analysis was performed to compare clinical characteristics between atherothrombotic and cardioembolic strokes. A DL method was designed based on two deep neural networks for: (1) image segmentation and (2) image classification including clinical characteristics. The metrics used were DICE coefficient for the segmentation network, and accuracy, precision, sensitivity, specificity and area under the curve (AUC) for the predictions of the classification network.

Results

A total of 166 patients (mean age 69 [SD, 13], 67 female) were included. TOAST classification was: 31 atherothrombotic, 87 cardioembolic, and 48 cryptogenic. The segmentation network achieved an average DICE coefficient of 0.96 [SD, 0.13]. The optimal fused imaging and clinical classification network had a 0.968 accuracy [95% CI, 0.935-0.994], and AUC of 0.947 [95% CI, 0.870-1]. Cryptogenic thrombi were classified as cardioembolic (96%) or atherothrombotic (4%).

Conclusion

Two convolutional neural networks perform the automatic segmentation of thrombus images and, combined with selected clinical characteristics, their accurate and precise classification into atherothrombotic or cardioembolic etiology in patients with acute ischemic stroke.

Clot signature in patients with large vessel occlusion stroke and concomitant active cancer

BACKGROUND AND PURPOSE

Patients with active cancer face an increased risk of ischemic stroke. Also, stroke may be an initial indicator of cancer. In patients with large vessel occlusion (LVO) stroke treated with thrombectomy, analysis of the clot composition may contribute new insights into the pathological connections between these two conditions.

METHODS

We compared the content of 64 consecutively retrieved clots from LVO stroke patients with concomitant active cancer and 64 clots from matched-control LVO stroke patients without a history of cancer. Clots were analyzed with respect to histological composition by Martius Scarlet Blue, von Willebrand factor (vWF), citrullinated histone H3 (H3Cit, a biomarker of NETS), CD42b, and CD3 expression by immunohistochemistry. Orbit Image Analysis was used for quantification. Differences between groups were tested using the Mann-Whitney U-test and Chi-square Test.

RESULTS

Clots from patients with concomitant cancer had a significantly higher content of vWF (median 26 [IQR13-38]% vs. 10 [4-18]%, p < 0.0001) and H3Cit (median 0.11 [IQR0.02-0.46]% vs. 0.05 [0.00-0.28]% p = 0.027) than controls. The presence of collagen >1% within the retrieved clots was highly indicative of cancer, occurring in 16/64 with active cancer and in 3/64 controls, p = 0.002. After correction for multiple comparisons, the statistical significance for H3Cit was lost. Red and white blood cells, platelets, fibrin, and expression of CD3 and CD42b did not differ between the groups.

CONCLUSIONS

Clots from LVO patients with concomitant active cancer possess distinct characteristics, indicating an influence of cancer on the innate immune system, fibroblasts, and the vascular endothelium in the formation of LVO clots.

Radiomics model based on dual-energy CT can determine the source of thrombus in strokes with middle cerebral artery occlusion

PURPOSE

To develop thrombus radiomics models based on dual-energy CT (DECT) for predicting etiologic cause of stroke.

METHODS

We retrospectively enrolled patients with occlusion of the middle cerebral artery who underwent computed tomography (NCCT) and DECT angiography (DECTA). 70 keV virtual monoenergetic images (simulate conventional 120kVp CTA images) and iodine overlay maps (IOM) were reconstructed for analysis. Five logistic regression radiomics models for predicting cardioembolism (CE) were built based on the features extracted from NCCT, CTA and IOM images. From these, the best one was selected to integrate with clinical information for further construction of the combined model. The performance of the different models was evaluated and compared using ROC curve analysis, clinical decision curves (DCA), calibration curves and Delong test.

RESULTS

Among all the radiomic models, model NCCT+IOM performed the best, with AUC = 0.95 significantly higher than model NCCT, model CTA, model IOM and model NCCT+CTA in the training set (AUC = 0.88, 0.78, 0.90,0.87, respectively, P < 0.05), and AUC = 0.92 in the testing set, significantly higher than model CTA (AUC = 0.71, P < 0.05). Smoking and NIHSS score were independent predictors of CE (P < 0.05). The combined model performed similarly to the model NCCT+IOM, with no statistically significant difference in AUC either in the training or test sets. (0.96 vs. 0.95; 0.94 vs. 0.92, both P > 0.05).

CONCLUSION

Radiomics models constructed based on NCCT and IOM images can effectively determine the source of thrombus in stroke without relying on clinical information.

Thrombus histology does not predict stroke etiological subtype but influences recanalization

BACKGROUND

There is conflicting data on whether clot retrieved from mechanical thrombectomy can predict stroke etiology or the success of recanalization. We aimed to analyse the relation between thrombus histology and stroke aetiology as well as recanalization.

METHODOLOGY

Histopathological analysis of clots retrieved from patients with acute ischemic stroke and large vessel occlusion was done. Quantification of the amount of fibrin, red blood cells(RBC), platelets and white blood cells (WBC) in the clots were done. The clinical, imaging data and recanalization parameters were collected. The correlation between clot composition and stroke etiology as well as recanalization were analysed.

RESULTS

Of the 77 patients, the mean age was 58. 67 ± 12.96 years. The stroke etiology were cardioembolism 44(57.1 %), large artery atherosclerosis 13(16.8 %), other determined aetiology 4(5.1 %) and undetermined in 16(20.7 %) patients. There was no significant correlation between the proportions of RBC-rich, platelet-rich and fibrin-rich thrombi and the stroke etiology. The susceptibility vessel sign was associated with RBC-rich clot(92.3 % vs 7.7 %, p = .03). All RBC-rich clots(100 %) had good recanalization(p = .05). Platelet-rich clots needed less number of passes(64.7 % vs 35.3 %, p = .006) and reduced groin puncture to recanalization time(87.9 % vs 12.1 %, p = .033). WBC-rich clots required lesser number of passes(57.5 % vs 42.5 %, P = .044). In multivariate analysis, WBC-rich clots (OR 0.230, CI 0.07-0.78, p = .018) showed an independent association with reduced recanalization attempts, while platelet-rich clots showed reduced recanalization time(OR 0.09, CI 0.01-0.63, p = .016).

CONCLUSION

There was no correlation between thrombus histology and the etiological stroke subtype. However, clot composition predicted the degree of recanalization and number of passes.

Cancer-Associated Stroke: Thrombosis Mechanism, Diagnosis, Outcome, and Therapeutic Strategies

Cancer can induce hypercoagulability, which may lead to stroke. This occurs when tumor cells activate platelets as part of their growth and metastasis. Tumor cells activate platelets by generating thrombin and expressing tissue factor, resulting in tumor cell-induced platelet aggregation. Histopathological studies of thrombi obtained during endovascular thrombectomy in patients with acute stroke and active cancer have shown a high proportion of platelets and thrombin. This underscores the crucial roles of platelets and thrombin in cancer-associated thrombosis. Cancer-associated stroke typically occurs in patients with active cancer and is characterized by distinctive features. These features include multiple infarctions across multiple vascular territories, markedly elevated blood D-dimer levels, and metastasis. The presence of cardiac vegetations on echocardiography is a robust indicator of cancer-associated stroke. Suspicion of cancer-associated stroke during endovascular thrombectomy arises when white thrombi are detected, particularly in patients with active cancer. Cancer-associated stroke is almost certain when histopathological examination of thrombi shows a very high platelet and a very low erythrocyte composition. Patients with cancer-associated stroke have high risks of mortality and recurrent stroke. However, limited data are available on the optimal treatment regimen for stroke prevention in these patients. Thrombosis mechanism in cancer is well understood, and distinct therapeutic targets involving thrombin and platelets have been identified. Therefore, direct thrombin inhibitors and/or antiplatelet agents may effectively prevent stroke recurrence. Additionally, this strategy has potential benefits in cancer treatment as accumulating evidence suggests that aspirin use reduces cancer progression, metastasis, and cancer-related mortality. However, clinical trials are necessary to assess the efficacy of this strategy involving the use of direct thrombin inhibitors and/or antiplatelet therapies.

A homogenized two-phase computational framework for meso- and macroscale blood flow simulations

BACKGROUND AND OBJECTIVE

Owing to the complexity of physics linked with blood flow and its associated phenomena, appropriate modeling of the multi-constituent rheology of blood is of primary importance. To this effect, various kinds of computational fluid dynamic models have been developed, each with merits and limitations. However, when additional physics like thrombosis and embolization is included within the framework of these models, computationally efficient scalable translation becomes very difficult. Therefore, this paper presents a homogenized two-phase blood flow framework with similar characteristics to a single fluid model but retains the flow resolution of a classical two-fluid model. The presented framework is validated against four different sets of experiments.

METHODS

The two-phase model of blood presented here is based on the classical diffusion-flux framework. Diffusion flux models are known to be less computationally expensive than two-fluid multiphase models since the numerical implementation resembles single-phase flow models. Diffusion flux models typically use empirical slip velocity correlations to resolve the motion between phases. However, such correlations do not exist for blood. Therefore, a modified slip velocity equation is proposed, derived rigorously from the two-fluid governing equations. An additional drag law for red blood cells (RBCs) as a function of volume fraction is evaluated using a previously published cell-resolved solver. A new hematocrit-dependent expression for lift force on RBCs is proposed. The final governing equations are discretized and solved using the open-source software OpenFOAM.

RESULTS

The framework is validated against four sets of experiments: (i) flow through a rectangular microchannel to validate RBC velocity profiles against experimental measurements and compare computed hematocrit distributions against previously reported simulation results (ii) flow through a sudden expansion microchannel for comparing experimentally obtained contours of hematocrit distributions and normalized cell-free region length obtained at different flowrates and inlet hematocrits, (iii) flow through two hyperbolic channels to evaluate model predictions of cell-free layer thickness, and (iv) flow through a microchannel that mimics crevices of a left ventricular assist device to predict hematocrit distributions observed experimentally. The simulation results exhibit good agreement with the results of all four experiments.

CONCLUSION

The computational framework presented in this paper has the advantage of resolving the multiscale physics of blood flow while still leveraging numerical techniques used for solving single-phase flows. Therefore, it becomes an excellent candidate for addressing more complicated problems related to blood flow, such as modeling mechanical entrapment of RBCs within blood clots, predicting thrombus composition, and visualizing clot embolization.

Differential expression of Semaphorin-7A /CD163-positive macrophages in large artery and cardiogenic stroke

BACKGROUND

Identification of the causes of stroke of undetermined etiology, specifically cardioembolism (CE) and non-CE causes, can inform treatment planning and prognosis prediction. The objective of this study was to analyze the disparities in thrombus composition, particularly Semaphorin-7A (Sema7A) and CD163, between patients diagnosed with large-artery atherosclerosis (LAA) and those with CE, and to investigate their potential association with prognosis.

METHODS

Thrombi were collected from patients who underwent mechanical thrombectomy at two hospitals. The patients were categorized into two groups: LAA and CE. We compared the levels of Sema7A and CD163 between these groups and analyzed their relationships with stroke severity, hemorrhagic transformation and prognosis.

RESULTS

The study involved a total of 67 patients. Sema7A expression was found to be significantly higher in the CE group compared to LAA (p < 0.001). Conversely, no statistically significant differences were observed for CD163 between the groups. The presence of Sema7A/CD163 did not show any associations with stroke severity or hemorrhagic transformation (all p > 0.05). However, both Sema7A (OR, 2.017; 95% CI, 1.301-3.518; p = 0.005) and CD163 (OR, 2.283; 95% CI, 1.252-5.724; p = 0.03) were associated with the poor prognosis for stroke, after adjusting for stroke severity.

CONCLUSION

This study highlights that CE thrombi exhibited higher levels of Sema7A expression compared to LAA thrombi. Moreover, we found a positive correlation between Sema7A/CD163 levels and the poor prognosis of patients with acute ischemic stroke.

Histologically interpretable clot radiomic features predict treatment outcomes of mechanical thrombectomy for ischemic stroke

PURPOSE

Radiomics features (RFs) extracted from CT images may provide valuable information on the biological structure of ischemic stroke blood clots and mechanical thrombectomy outcome. Here, we aimed to identify RFs predictive of thrombectomy outcomes and use clot histomics to explore the biology and structure related to these RFs.

METHODS

We extracted 293 RFs from co-registered non-contrast CT and CTA. RFs predictive of revascularization outcomes defined by first-pass effect (FPE, near to complete clot removal in one thrombectomy pass), were selected. We then trained and cross-validated a balanced logistic regression model fivefold, to assess the RFs in outcome prediction. On a subset of cases, we performed digital histopathology on the clots and computed 227 histomic features from their whole slide images as a means to interpret the biology behind significant RF.

RESULTS

We identified 6 significantly-associated RFs. RFs reflective of continuity in lower intensities, scattered higher intensities, and intensities with abrupt changes in texture were associated with successful revascularization outcome. For FPE prediction, the multi-variate model had high performance, with AUC = 0.832 ± 0.031 and accuracy = 0.760 ± 0.059 in training, and AUC = 0.787 ± 0.115 and accuracy = 0.787 ± 0.127 in cross-validation testing. Each of the 6 RFs was related to clot component organization in terms of red blood cell and fibrin/platelet distribution. Clots with more diversity of components, with varying sizes of red blood cells and fibrin/platelet regions in the section, were associated with RFs predictive of FPE.

CONCLUSION

Upon future validation in larger datasets, clot RFs on CT imaging are potential candidate markers for FPE prediction.

Effect of plasma thrombin-antithrombin complex on ischemic stroke: a systematic review and meta-analysis

BACKGROUND AND OBJECTIVE

Thrombin-antithrombin complex (TAT) is a prethrombotic marker, and its application in ischemic stroke is still uncertain. The purpose of this systematic review and meta-analysis is to evaluate the relationship between plasma TAT and ischemic stroke base on the current evidence.

METHODS

A systematic literature search was conducted for searching the relative studies that investigated the association of TAT and ischemic stroke in PubMed, EMBASE, and Cochrane library databases. Mean difference and 95% confidence interval as the effect sizes were synthesized by random effects model in Review Manager (RevMan) Version 5.4. The heterogeneity was investigated using the chi-square test and the possible sources of heterogeneity were explored by sensitivity analysis and meta-regression. The publication bias was estimated by Egger's tests.

RESULTS

A total of 12 eligible studies were included involving 1431 stroke cases and 532 healthy controls, of which six studies were eventually included in the meta-analysis. Plasma TAT in patients with ischemic stroke was significantly higher than that in healthy controls (MD 5.31, 95% CI = 4.12-6.51, P < 0.0001, I² = 97.8%). There is a difference of TAT level in the same period among cardioembolic, lacunar, and atherothrombotic stroke (all P < 0.0001), in which the cardioembolic stroke with the highest level. Meanwhile, it is significant of TAT levels among various phases of cardioembolic stroke and the acute phase are markedly elevated (MD 7.75, 95CI%, 6.07-9.43, P < 0.001). However, no difference was found in the atherothrombotic (P = 0.13) and lacunar stroke (P = 0.34). Besides, the higher TAT level is closely related to the poor prognosis of patients with ischemic stroke, including higher recurrence, mortality, unfavorable recovery (modified Rankin scale > 2), and poor revascularization.

CONCLUSIONS

This study suggested that plasma TAT levels are different in ischemic stroke subtypes, which are closely associated with the progression and might have an effect on the prognosis.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD: 42021248787.

Shell Versus Core Architecture and Biology of Thrombi in Acute Ischemic Stroke: A Systematic Review

BACKGROUND

The presence of an outer shell has been recently described as a common feature of acute ischemic stroke (AIS) thrombi. We performed a systematic review of the current literature on shell genesis, structure, and clinical significance.

METHODS

Following PRISMA guidelines, we searched Ovid Cochrane Central Register of Controlled Trials, Embase, Medline, Scopus, and Web of Science for studies reporting the composition and structure of AIS thrombi and clot analogs. Identified studies were added to Covidence software for primary screening. Two reviewers independently screened titles and abstracts followed by full-text screening.

RESULTS

From 1290 identified studies, 10 were included in this review. Studies using histology/immunohistochemistry/immunofluorescence described fibrin, platelets, von Willebrand factor, and neutrophil extracellular traps as the main components of the shell. Scanning electron microscopy demonstrated a dense, compact fibrin/platelet-rich shell, and a core rich in polyhedrocytes. Microfluidics studies identified highly activated P-selectin-positive platelets and fibrin forming the core while secondary agonists adenosine diphosphate and thromboxane, along with loosely packed P-selectin-negative platelets constituted the shell.

CONCLUSIONS

The composition, compaction, and integrity of the shell may impact thrombolysis and revascularization outcomes. The preponderance of studies supported this conclusion.

Cholesterol Crystals in the Retrieved Thrombus by Mechanical Thrombectomy for Cerebral Embolism: A Case Report and Literature Review

There are only a few case reports in which cholesterol crystals were found in the thrombus retrieved by mechanical thrombectomy for cryptogenic stroke, leading to a definitive diagnosis. We herein report a case of aortogenic embolic stroke diagnosed by the presence of rich cholesterol crystals in the retrieved thrombus and review the previously reported cases. A woman in her 80s was transferred as an emergency due to consciousness disturbance, right conjugate deviation, and severe left hemiparesis. Magnetic resonance imaging showed occlusion of the right middle cerebral artery (MCA) and acute infarction in the territory. The MCA was recanalized by thrombectomy using an aspiration catheter and stent retriever, and the symptoms improved. Although the physiological examination did not detect the embolic source during hospitalization, pathological examination of the thrombus revealed atheroma with numerous cholesterol crystal clefts and intermixing of fibrin. Contrast-enhanced computed tomography performed based on the pathological results showed atheromatous lesions in the aortic arch as the embolic source. As a subsequent treatment, medications of a strong statin and an antiplatelet agent were continued, and the patient had no recurrence. The finding that the retrieved thrombus is a simple atheroma containing cholesterol crystals with poor hemocytes suggests embolism due to plaque rupture. Pathological examination of the thrombus obtained by thrombectomy is one of the useful diagnostic approaches for stroke etiology and the determination of its treatment.

Clot Morphology in Acute Ischemic Stroke Decision Making

Stroke is a leading cause of death and disability in the world, and the provision of reperfusion therapy and endovascular therapy, in particular, have revolutionized the treatment of patients with stroke and opened opportunities to look at brain clots retrieved after the procedure. The use of histopathology and molecular profiling of clots is of growing research and clinical interest. However, its clinical implications and incorporation within stroke workflows remain suboptimal. Recent studies have indicated that the study of brain clots may inform the mechanism of stroke and hence guide treatment decision-making in select groups of patients, especially patients without a defined cause or known mechanism. This article provides a comprehensive overview of various clot histopathological examinations in acute stroke-care settings, their clinical utility, and existing gaps and opportunities for further research. We also provide targeted recommendations to improve clot analysis workflow, hence standardizing its incorporation into clinical practice.

Age and composition of the thrombus retrieved by mechanical thrombectomy from patients with acute ischemic stroke are associated with revascularization and clinical outcomes

INTRODUCTION

Understanding the composition of stroke thrombi retrieved by mechanical thrombectomy is essential to clarify the pathogenesis of stroke. However, it is difficult to evaluate thrombus composition precisely and objectively. Immunohistochemical staining was used to evaluate thrombus composition and age.

MATERIALS AND METHODS

Consecutive thrombi (n = 108) retrieved from patients who underwent mechanical thrombectomy for acute large-vessel ischemic stroke were retrospectively analyzed. Lytic features of granulocytes and CD163 were estimated as indicators of the age of the cardioembolic (CE) thrombus.

RESULTS

The stroke subtypes were as follows: CE, 74 cases; large artery atherosclerosis, 11; undetermined etiology, 12; and other determined etiology, 11. There were no statistical differences in thrombi composition according to stroke subtypes. The fibrin area was positively correlated with the red blood cell (RBC) and platelet areas. The following analysis was performed using CE only. Regarding age, the thrombus was judged as fresh in 30.0 % and older in 70.0 % based on the lytic features. The RBC areas of older thrombi were smaller than those of fresh thrombi. The puncture-to-reperfusion time of older thrombi was longer than that of fresh thrombi. Platelet-rich thrombi were associated with a greater number of maneuvers, a smaller prevalence of TICI 3, and unfavorable functional outcomes compared to platelet-poor thrombi. The number of CD163 positive cells in thrombi with anticoagulants was higher than in those without anticoagulants.

CONCLUSION

Thrombus composition correlated with revascularization and clinical outcomes. The composition of an acute ischemic thrombus may reflect the pathophysiology of stroke and influence treatment efficacy.

High Actin Expression in Thrombus of Acute Ischemic Stroke Can Be a Biomarker of Atherothrombotic Origin Stroke

Background

As the treatment target, the imaging information and histologic characteristics of the thrombus may differ according to the stroke subtype. This study aimed to provide the correlative study of stroke etiology with the non-contrast CT, and histological composition of retrieved clots in acute ischemic stroke (AIS).

Materials and Methods

A total of 94 patients with AIS who underwent the endovascular treatment with successfully retrieved clots from January 2017 to October 2020 were enrolled in the present study. Histological analysis was performed using hematoxylin and eosin (H&E) staining and immunostaining with CD3, CD20, CD105, and actin antibodies. CT obtained at the patients' admission was to measure the attenuation and volume of all thrombus.

Results

A total of 94 subjects were included in this study. Fifty-six patients were classified as cardioembolic (CE), and 38 were classified with large-artery atherosclerosis (LAA). The subjects with LAA tend to exhibit higher actin and CD105 levels, and lower Hounsfield Unit (HU) values than subjects with CE. After adjusting for confounders, the actin was positively correlated with CD105 but not with HU values. Logistics regression shows actin was valuable for the prediction of LAA (OR, 1.148; 95% CI, 1.075–1.227; p < 0.001), even adjusted for age, sex, and intervention type (OR, 1.129; 95% CI, 1.048–1.216; p = 0.001), CT density and CD105 (OR, 1.161; 95% CI, 1.056–1.277; p = 0.002). Actin levels have a strong accuracy in differentiating LAA from CE, especially combined with CT density and CD105, which yielded a sensitivity of 63.2%, a specificity of 89.3%, with the area under the curve (AUC) at 0.821 (95% CI, 0.731–0.912).

Conclusion

Our findings suggest that actin's level was a major factor differentiating atherothrombotic origin strokes from the cardioembolic stroke.

Clinical Trial Registration

ChiCTR2100051173.

Correlation of von Willebrand factor and platelets with acute ischemic stroke etiology and revascularization outcome: an immunohistochemical study

BACKGROUND

Platelets and von Willebrand factor (vWF) are key components of acute ischemic stroke (AIS) emboli. We aimed to investigate the CD42b (platelets)/vWF expression, its association with stroke etiology and the impact these components may have on the clinical/procedural parameters.

METHODS

CD42b/vWF immunostaining was performed on 288 emboli collected as part of the multicenter STRIP Registry. CD42b/VWF expression and distribution were evaluated. Student's t-test and χ² test were performed as appropriate.

RESULTS

The mean CD42b and VWF content in clots was 44.3% and 21.9%, respectively. There was a positive correlation between platelets and vWF (r=0.64, p<0.001**). We found a significantly higher vWF level in the other determined etiology (p=0.016*) and cryptogenic (p=0.049*) groups compared with cardioembolic etiology. No significant difference in CD42b content was found across the etiology subtypes. CD42b/vWF patterns were significantly associated with stroke etiology (p=0.006*). The peripheral pattern was predominant in atherosclerotic clots (36.4%) while the clustering (patchy) pattern was significantly associated with cardioembolic and cryptogenic origin (66.7% and 49.8%, respectively). The clots corresponding to other determined etiology showed mainly a diffuse pattern (28.1%). Two types of platelets were distinguished within the CD42b-positive clusters in all emboli: vWF-positive platelets were observed at the center, surrounded by vWF-negative platelets. Thrombolysis correlated with a high platelet content (p=0.03*). vWF-poor and peripheral CD42b/vWF pattern correlated with first pass effect (p=0.03* and p=0.04*, respectively).

CONCLUSIONS

The vWF level and CD42b/vWF distribution pattern in emboli were correlated with AIS etiology and revascularization outcome. Platelet content was associated with response to thrombolysis.