Histopathologic composition of cerebral thrombi of acute stroke patients is correlated with stroke subtype and thrombus attenuation

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.

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

BACKGROUND

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).

METHODS

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.

RESULTS

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).

CONCLUSIONS

Proteomics can offer new insights into the close relationship between thrombus composition and susceptibility to fibrinolysis, paving the way for new adjuvant therapies.

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.

Correlation between thrombus composition and regulatory T cell counts with clinical outcomes of acute ischemic stroke patients with thrombectomy

OBJECTIVES

To analyze the relationship of thrombus composition and regulatory T cell expression with clinical outcome in acute ischemic stroke (AIS) patients with thrombectomy.

METHODS

A total of 44 AIS patients who underwent thrombectomy in the Department of Neurology of Shaoxing Hospital from June 2021 to October 2022 were enrolled. All thrombus specimens were subjected to hematoxylin-eosin staining and immunohistochemistry. Semi-quantitative analysis was performed to determine the content of red blood cells, fibrinogen/platelets, and regulatory T (CD4+CD25+) cells. Clinical data, vascular recanalization status, and neurologic outcomes at 3 months after thrombectomy were collected. A modified Rankin Scale score of 0-2 was defined as a favorable outcome.

RESULTS

Among 44 patients with complete thrombus data there were 15 cases of red cell type, 11 cases of mixed type and 18 cases of fibrin/platelet type. There was a significant difference in trial of ORG 10172 in acute stroke treatment (TOAST) etiological classification among the three groups (P<0.01), while no significant differences were found in other general clinical and surgical data (all P>0.05). According to the TOAST etiology, 28 cases were classified as large atherosclerosis type and 16 cases as cardioembolic type. The proportion of red blood cells in thrombus was significantly higher in patients with large atherosclerosis type than that in those with cardioembolic type [58.0% (44.2%, 72.5%) vs. 24.5% (12.7%, 48.0%), P<0.01]. The ratio of fibrin to platelet in patients with cardiogenic embolism was significantly higher than that in patients with large atherosclerosis [73.0% (49.2%, 84.5%) vs. 40.0% (25.2%, 54.5%), P<0.01). Among the 44 patients, 19 had good while 25 had poor neurological outcomes. Univariate binary logistic regression analysis showed that age, operation time, CD4+CD25+T cell number were correlated with the functional outcomes of the patients (all P<0.05). Multivariate binary logistic regression analysis showed that thrombus CD4+CD25+T cell count was an independent factor affecting the functional outcome of patients (OR=1.369, 95%CI: 1.101-1.701, P<0.01).

CONCLUSIONS

There is no significant correlation of erythrocyte and fibrin/platelet components in thrombus with functional outcome in AIS patients, but an increased count of regulatory T cells associates with good functional outcome.

White blood cell subtypes and neutrophil extracellular traps content as biomarkers for stroke etiology in acute ischemic stroke clots retrieved by mechanical thrombectomy

BACKGROUND

Lymphocytes, macrophages, neutrophils, and neutrophil extracellular traps (NETs) associate with stroke risk factors and form a thrombus through different mechanisms. We investigated the total WBCs, WBC subtypes and NETs composition in acute ischemic stroke (AIS) clots to identify possible etiological differences that could help us further understand the process of thrombosis that leads to AIS.

METHODS

AIS clots from 100 cases each of atherothrombotic (AT), cardioembolic (CE) and cryptogenic stroke etiology were collected per-pass as part of the CÚRAM RESTORE registry of AIS clots. Martius Scarlet Blue stain was used to identify the main histological components of the clots. Immunohistochemical staining was used to identify neutrophils, lymphocytes, macrophages, and NETs patterns. The cellular and histological components were quantified using Orbit Image Analysis software.

RESULTS

AT clots were larger, with more red blood cells and fewer WBCs than CE clots. AT clots had more lymphocytes and cryptogenic clots had fewer macrophages than other etiologies. Most significantly, CE clots showed higher expression of neutrophils and extracellular web-like NETs compared to AT and cryptogenic clots. There was also a significantly higher distribution of web-like NETs around the periphery of the CE clots while a mixed distribution was observed in AT clots.

CONCLUSION

The difference in neutrophil and NETs expression in clots from different etiologies may provide insight into the mechanism of clot formation.

Adhesion of vessel wall to stentriever during combined technique for mechanical thrombectomy in acute ischemic stroke: A histomorphological study

PURPOSE

Detection of vessel wall tissue in thrombus material in patients with ischemic stroke is judged as vascular injury. So far, several studies investigated components of the free clots after mechanical thrombectomy. The aim of this retrospective study was to investigate the involvement and role of the stentriever in vessel wall injury by analysis of the composition of adherent tissue to the stentriever during combined aspiration thrombectomy with stentriever.

METHODS

Stentriever with adherent tissue and free clots in aspiration samples from patients undergoing mechanical thrombectomy (aspiration plus stentriever) were separately assessed for the occurrence of parts of vascular tissue together with clinical and interventional data as well as clinical outcome data. Specimens were analyzed histomorphologically and immunohistochemically. Findings, focused on parts of vessel wall were reported together with clinical data.

RESULTS

Specimens from 21 identified patients were available. Parts of the vessel wall were detected in 7 out 21 (33%) samples. All specimens revealed fresh thrombus material without signs of organization or atheromatous tissue. In 90% of patients mTICI was greater than 2b without signs of secondary vessel injury. No vascular tissue was found in free clots of the aspiration samples.

CONCLUSION

The examination of adherent tissue to the stentriever instead of the examination of free clots may affect the number of detected parts of vessel wall. Further studies in combination with vessel wall imaging may elucidate the origin of remnants of vessel wall.

CT hyperdense cerebral artery sign reflects distinct proteomic composition in acute ischemic stroke thrombus

BACKGROUND

Hyperdense cerebral artery sign (HCAS) is an imaging biomarker in acute ischemic stroke (AIS) that has been shown to be associated with various clinical outcomes and stroke etiology. While prior studies have correlated HCAS with histopathological composition of cerebral thrombus, it is unknown whether and to what extent HCAS is also associated with distinct clot protein composition.

METHODS

Thromboembolic material from 24 patients with AIS were retrieved via mechanical thrombectomy and evaluated with mass spectrometry in order to characterize their proteomic composition. Presence (+) or absence (-) of HCAS on preintervention non-contrast head CT was then determined and correlated with thrombus protein signature with abundance of individual proteins calculated as a function HCAS status.

RESULTS

24 clots with 1797 distinct proteins in total were identified. 14 patients were HCAS(+) and 10 were HCAS(-). HCAS(+) were most significantly differentially abundant in actin cytoskeletal protein (P=0.002, Z=2.82), bleomycin hydrolase (P=0.007, Z=2.44), arachidonate 12-lipoxygenase (P=0.004, Z=2.60), and lysophospholipase D (P=0.007, Z=2.44), among other proteins; HCAS(-) clots were differentially enriched in soluble N-ethylmaleimide-sensitive factor (NSF) attachment protein (P=0.0009, Z=3.11), tyrosine-protein kinase Fyn (P=0.002, Z=2.84), and several complement proteins (P<0.05, Z>1.71 for all), among numerous other proteins. Additionally, HCAS(-) thrombi were enriched in biological processes involved with plasma lipoprotein and protein-lipid remodeling/assembling, and lipoprotein metabolic processes (P<0.001), as well as cellular components including mitochondria (P<0.001).

CONCLUSIONS

HCAS is reflective of distinct proteomic composition in AIS thrombus. These findings suggest that imaging can be used to identify mechanisms of clot formation or maintenance at the protein level, and might inform future research on thrombus biology and imaging characterization.

The association between human blood clot analogue computed tomography imaging, composition, contraction, and mechanical characteristics

BACKGROUND

Clot composition, contraction, and mechanical properties are likely determinants of endovascular thrombectomy success. A pre-interventional estimation of these properties is hypothesized to aid in selecting the most suitable treatment for different types of thrombi. Here we determined the association between the aforementioned properties and computed tomography (CT) characteristics using human blood clot analogues.

METHODS

Clot analogues were prepared from the blood of 4 healthy human donors with 5 red blood cell (RBC) volume suspensions: 0%, 20%, 40%, 60% and 80% RBCs. Contraction was measured as the weight of the contracted clots as a percentage of the original suspension. The clots were imaged using CT with and without contrast to quantify clot density and density increase. Unconfined compression was performed to determine the high strain compressive stiffness. The RBC content was analysed using H&E staining.

RESULTS

The 5 RBC suspensions formed only two groups of clots, fibrin-rich (0% RBCs) and RBC-rich (>90% RBCs), as determined by histology. The density of the fibrin-rich clots was significantly lower (31-38HU) compared to the RBC-rich clots (72-89HU), and the density increase of the fibrin-rich clots was significantly higher (82-127HU) compared to the RBC-rich clots (3-17HU). The compressive stiffness of the fibrin-rich clots was higher (178-1624 kPa) than the stiffness of the RBC-rich clots (6-526 kPa). Additionally, the degree of clot contraction was higher for the fibrin-rich clots (89-96%) compared to the RBC-rich clots (11-77%).

CONCLUSIONS

CT imaging clearly reflects clot RBC content and seems to be related to the clot contraction and stiffness. CT imaging might be a useful tool in predicting the thrombus characteristics. However, future studies should confirm these findings by analysing clots with intermediate RBC and platelet content.

Prognostic Value of Histopathological Thrombus Age in Large Vessel Occlusion-Related Stroke

INTRODUCTION

Acute mechanical thrombectomy (MT) is the preferred treatment for large vessel occlusion-related stroke. Histopathological research on the obtained occlusive embolic thrombus may provide information regarding the aetiology and pathology of the lesion to predict prognosis and propose possible future acute ischaemic stroke therapy.

METHODS

A total of 75 consecutive patients who presented to the Amphia Hospital with acute large vessel occlusion-related stroke and underwent MT were included in the study. The obtained thrombus materials were subjected to standard histopathological examination. Based on histological criteria, they were considered fresh (<1 day old) or old (>1 day old). Patients were followed for 2 years for documentation of all-cause mortality.

RESULTS

Thrombi were classified as fresh in 40 patients (53%) and as older in 35 patients (47%). Univariate Cox regression analysis showed that thrombus age, National Institutes of Health Stroke Scale at hospital admission, and patient age were associated with long-term mortality (p < 0.1). Multivariable Cox hazards and Kaplan-Meier analysis demonstrated that after extensive adjustment for clinical and procedural variables, thrombus age persisted in being independently associated with higher long-term mortality (hazard ratio: 3.34; p = 0.038, log-rank p = 0.013).

CONCLUSION

In this study, older thromboemboli are responsible for almost half of acute large ischaemic strokes. Moreover, the presence of an old thrombus is an independent predictor of mortality in acute large vessel occlusion-related stroke. More research is warranted regarding future therapies based on thrombus composition.

The Value of Dual-Energy Computed Tomography Angiography-Derived Parameters in the Evaluation of Clot Composition

OBJECTIVES

We aimed to assess the value of dual-energy computed tomography angiography (DE-CTA) derived parameters as a quantitative biomarker of thrombus composition in acute ischemic stroke (AIS).

METHODS

AIS patients who underwent DE-CTA before thrombectomy between August 2016 and September 2022 were included in this study. We assessed the relative proportion of red blood cells (RBCs) and the fibrin/platelet ratio (F/P) of the retrieved clots and categorized the clots as RBC-dominant (RBCs > F/P) or F/P-dominant (F/P > RBCs). The thrombus based parameters were measured on polyenergetic images (PEI), virtual monoenergetic (VM), virtual non-contrast (VNC), iodine concentration (IC), and effective atomic number (Zeff) images respectively, and the slope of the spectral Hounsfield unit curve (λHU) was calculated. These parameters were compared in the DE-CTA images of RBC- and F/P-dominant thrombi. The diagnostic performance of the parameters was analyzed using the ROC curve. Correlations between thrombus composition and DE-CTA-derived parameters were assessed.

RESULTS

The retrieved clots in 54 of 88 patients (61.36%) were RBC-dominant. The RBC-dominant thrombi showed significantly higher VNC values and lower IC, λHU, and Zeff values than the F/P-dominant thrombi (p < 0.05). The CT density measured on IC images showed the largest AUC value (AUC, 0.94; sensitivity, 77.78%; specificity, 100.00%). The Spearman rank-order correlation coefficient values showed that CT density measured on IC images of the thrombus showed the strongest association with the proportion of RBCs (r = -0.64, p < 0.001) and F/P (r = 0.65, p < 0.001).

CONCLUSIONS

DE-CTA-derived parameters, especially the CT density measured on IC images, could be associated with thrombus composition and allow for personalized thrombectomy strategies.

Utility of dual energy CT in differentiating clot in acute ischemic stroke

PURPOSE

Red blood cells (RBC)-poor thrombi in acute ischemic stroke (AIS) are associated with longer recanalization time for mechanical thrombectomy than RBC-rich thrombi. The purpose of the study was to differentiate between RBC-rich and RBC-poor thrombi using dual energy computed tomography (DECT).

MATERIALS AND METHODS

This retrospective study was conducted on patients with acute arterial occlusion of anterior circulation who underwent DECT cerebral angiography, followed by mechanical thrombectomy with the pathological diagnosis of thrombi, dividing into RBC-rich and RBC-poor thrombi. The CT attenuation values and thrombus enhancement were measured in non-contrast scans and CTA phases at different energy levels and compared between RBC-rich and RBC-poor groups.

RESULTS

Fourteen acute stroke patients were included in the study. There were 7 patients in RBC-rich group and 7 patients in RBC-poor group. The CT attenuation values of RBC-rich thrombi were significantly higher than those of RBC-poor thrombi at energy levels of 40, 50, 60, 70, and 80 KeV, with the most significant difference at 80 KeV (p = 0.032). A cutoff value of 44.1 Hounsfield units (HU) on 80 keV monoenergetic reconstructions was used to distinguish between RBC-rich and RBC-poor thrombi. It achieved an area under the curve (AUC) of 0.878, sensitivity of 85.7%, specificity of 100%, and accuracy of 92.9%. The degree of enhancement was higher in RBC-poor thrombi than in RBC-rich thrombi, without statistically significant difference.

CONCLUSION

DECT could help differentiate between RBC-rich and RBC-poor thrombi by using CT attenuation values in non-contrast phase at lower energy levels (40-80 KeV).

Imaging diagnosis of intracranial atherosclerosis stenosis-related large vessel occlusion before and during endovascular therapy

It is becoming increasingly important to identify the type of stroke, especially the mechanism of occlusion, before and during its treatment. In the case of intracranial atherosclerotic stenosis-related large vessel occlusion, it is necessary to develop a treatment strategy that includes not only mechanical thrombectomy but also adjunctive therapies such as primary or rescue therapy (percutaneous angioplasty, intracranial/carotid stenting, local fibrinolysis) and perioperative antithrombotic therapy. However, in clinical practice we often encounter cases where it is difficult to identify the occlusive mechanism before endovascular treatment because of insufficient information in the minimal circumstances of the hyperacute phase of stroke. Here we focus on the imaging diagnosis before and during treatment of intracranial atherosclerotic stenosis-related large vessel occlusion with in situ thrombotic occlusion as the mechanism of thrombotic occlusion, based on previous reports. We describe the diagnosis of intracranial atherosclerotic stenosis-related large vessel occlusion from the perspectives of "thrombus imaging," "perfusion," and "occlusion margin."

Large Vessel Occlusion Stroke due to Intracranial Atherosclerotic Disease: Identification, Medical and Interventional Treatment, and Outcomes

Large vessel occlusion stroke due to underlying intracranial atherosclerotic disease (ICAD-LVO) is prevalent in 10 to 30% of LVOs depending on patient factors such as vascular risk factors, race and ethnicity, and age. Patients with ICAD-LVO derive similar functional outcome benefit from endovascular thrombectomy as other mechanisms of LVO, but up to half of ICAD-LVO patients reocclude after revascularization. Therefore, early identification and treatment planning for ICAD-LVO are important given the unique considerations before, during, and after endovascular thrombectomy. In this review of ICAD-LVO, we propose a multistep approach to ICAD-LVO identification, pretreatment and endovascular thrombectomy considerations, adjunctive medications, and medical management. There have been no large-scale randomized controlled trials dedicated to studying ICAD-LVO, therefore this review focuses on observational studies.

Negative susceptibility vessel sign might be predictive of complete reperfusion in patients with acute basilar artery occlusion managed with thrombectomy

OBJECTIVES

Negative susceptibility vessel sign (SVS) on pre-thrombectomy MRI has been linked to fibrin-rich thrombus and difficult retrieval in anterior ischemic stroke. However, its impact in posterior circulation-large vessel occlusion stroke (PC-LVOS) has not yet been elucidated. We aim to investigate the relationship of SVS parameters with stroke subtypes and their influence on angiographic and functional outcomes.

METHODS

Prospective thrombectomy registries at two-comprehensive stroke centers were retrospectively reviewed between January 2015 and December 2019 for consecutive MRI-selected patients with PC-LVOS. Two groups were assigned by two independent readers, based on the presence or absence of the SVS (SVS +, SVS -) on MRI-GRE sequence. Multivariate logistic regression analysis was utilized to study primarily the impact of the SVS on the rate of complete recanalization (defined as mTICI 2c/3) at the final series following endovascular thrombectomy (EVT) and whether or not it might influence the efficacy of the frontline EVT strategy. Secondarily, we studied whether the absence of the SVS was predictive of the rate of 90-day functional independence (defined as mRS score < 2). Lastly, both qualitative (SVS +, SVS-) and quantitative (SVS length and diameter) parameters of the SVS were analyzed in association with the puncture to recanalization interval and various stroke etiological subtypes based on TOAST criteria.

RESULTS

Among 1823 patients, 116 were qualified for final analysis (median age, 68 (59-75) years; male, 65%); SVS was detected in 62.9% (73/116) of cases. SVS length was an independent predictor of procedural duration (p = .01) whilst two-layered SVS was inversely associated with the atherosclerosis etiological subtype (aOR = 0.27, 95% CI 0.08-0.89; p = .03). Successful recanalization was achieved in 82% (60/73) vs. 86% (37/43), p = .80 of patients with SVS (+, -) respectively. Only in SVS (+), stentriever (RR 0.59 (0.4-0.88), p = .009), and contact-aspiration (RR 0.82 (0.7-0.96), p = .01) achieved a lower rate of successful recanalization compared to combined technique. SVS (-) was significantly associated with a higher rate of mTICI 2c/3 (aOR = 4.444; 95% CI 1.466-13.473; p = .008) and showed an indirect effect of 9% towards functional independence mediated by mTICI 2c/3.

CONCLUSION

SVS parameters in PC-LVOS might predict stroke subtype and indirectly influence the functional outcome by virtue of complete recanalization.

KEY POINTS

• Negative susceptibility vessel sign (SVS) in patients with basilar occlusion independently predict complete recanalization that indirectly instigated a 3-month favorable outcome following thrombectomy. • The longer the SVS, the higher likelihood of large artery atherosclerosis and the longer the thrombectomy procedure. • Two-layered SVS might be negatively associated with the presence of atherosclerosis, yet already-known limitations of TOAST classification and the absence of pathological analysis should be taken into consideration.

Nanotechnology in Stroke: New Trails with Smaller Scales

Stroke is a leading cause of death, long-term disability, and socioeconomic costs, highlighting the urgent need for effective treatment. During acute phase, intravenous administration of recombinant tissue plasminogen activator (tPA), a thrombolytic agent, and endovascular thrombectomy (EVT), a mechanical intervention to retrieve clots, are the only FDA-approved treatments to re-establish cerebral blood flow. Due to a short therapeutic time window and high potential risk of cerebral hemorrhage, a limited number of acute stroke patients benefit from tPA treatment. EVT can be performed within an extended time window, but such intervention is performed only in patients with occlusion in a larger, anatomically more proximal vasculature and is carried out at specialty centers. Regardless of the method, in case of successful recanalization, ischemia-reperfusion injury represents an additional challenge. Further, tPA disrupts the blood-brain barrier integrity and is neurotoxic, aggravating reperfusion injury. Nanoparticle-based approaches have the potential to circumvent some of the above issues and develop a thrombolytic agent that can be administered safely beyond the time window for tPA treatment. Different attributes of nanoparticles are also being explored to develop a multifunctional thrombolytic agent that, in addition to a thrombolytic agent, can contain therapeutics such as an anti-inflammatory, antioxidant, neuro/vasoprotective, or imaging agent, i.e., a theragnostic agent. The focus of this review is to highlight these advances as they relate to cerebrovascular conditions to improve clinical outcomes in stroke patients.

An old thrombus may potentially identify patients at higher risk of poor outcome in anterior circulation stroke undergoing thrombectomy

PURPOSE

To investigate thrombus age and its association with clinical and procedural parameters in patients with acute ischemic stroke (AIS) due to anterior circulation occlusions.

METHODS

The thrombi of 107 consecutive AIS patients with occlusions in anterior circulation large-arteries were collected during mechanical recanalization. By hematoxylin-eosin staining analysis, thrombi were classified as fresh (< 3 days) or old (≥ 3 days) according to the hemosiderin positivity. Old thrombi were further classified as thrombi with focal hemosiderin or diffuse hemosiderin according to their predominant distribution. Neuro-interventional data and clinical outcomes were compared based on thrombus age.

RESULTS

We identified fresh thrombi in 29 patients and old thrombi in 78 patients. Compared with patients with fresh thrombi, patients with old thrombi were associated with (i) a longer mechanical recanalization time (p = 0.027), (ii) a higher percentage of fibrin/platelets and leukocytes (all p = 0.02) and a lower percentage of erythrocytes (p = 0.001), and (iii) less favorable clinical outcomes at discharge (p = 0.019) and 90 days later (OR = 2.76, 95% CI = 1.09-6.99, p = 0.032). Furthermore, 18 (16.8%) of all patients had focal hemosiderin in old thrombi, which was independently linked to a poor clinical outcome 90 days later (adjusted OR = 5.37, 95% CI = 1.14-25.28, p = 0.034).

CONCLUSION

The presence of old thrombi, particularly those with focal hemosiderin, may aid in identifying patients with acute ischemic anterior circulation stroke who are at a higher risk of poor clinical outcome at 3-month follow-up.

Clot-based radiomics model for cardioembolic stroke prediction with CT imaging before recanalization: a multicenter study

OBJECTIVES

To develop a clot-based radiomics model using CT imaging radiomic features and machine learning to identify cardioembolic (CE) stroke before mechanical thrombectomy (MTB) in patients with acute ischemic stroke (AIS).

MATERIALS AND METHODS

This retrospective four-center study consecutively included 403 patients with AIS who sequentially underwent CT and MTB between April 2016 and July 2021. These were grouped into training, testing, and external validation cohorts. Thrombus-extracted radiomic features and basic information were gathered to construct a machine learning model to predict CE stroke. The radiological characteristics and basic information were used to build a routine radiological model. A combined radiomics and radiological features model was also developed. The performances of all models were evaluated and compared in the validation cohort. A histological analysis helped further assess the proposed model in all patients.

RESULTS

The radiomics model yielded an area under the curve (AUC) of 0.838 (95% confidence interval [CI], 0.771-0.891) for predicting CE stroke in the validation cohort, significantly higher than the radiological model (AUC, 0.713; 95% CI, 0.636-0.781; p = 0.007) but similar to the combined model (AUC, 0.855; 95% CI, 0.791-0.906; p = 0.14). The thrombus radiomic features achieved stronger correlations with red blood cells (|r_max|, 0.74 vs. 0.32) and fibrin and platelet (|r_max|, 0.68 vs. 0.18) than radiological characteristics.

CONCLUSION

The proposed CT-based radiomics model could reliably predict CE stroke in AIS, performing better than the routine radiological method.

KEY POINTS

• Admission CT imaging could offer valuable information to identify the acute ischemic stroke source by radiomics analysis. • The proposed CT imaging-based radiomics model yielded a higher area under the curve (0.838) than the routine radiological method (0.713; p = 0.007). • Several radiomic features showed significantly stronger correlations with two main thrombus constituents (red blood cells, |r_max|, 0.74; fibrin and platelet, |r_max|, 0.68) than routine radiological characteristics.

Machine Learning Analysis of the Cerebrovascular Thrombi Lipidome in Acute Ischemic Stroke

ABSTRACT

OBJECTIVE: The aim of this study was to identify a signature lipid profile from cerebral thrombi in acute ischemic stroke (AIS) patients at the time of ictus. METHODS: We performed untargeted lipidomics analysis using liquid chromatography-mass spectrometry on cerebral thrombi taken from a nonprobability, convenience sampling of adult subjects (≥18 years old, n = 5) who underwent thrombectomy for acute cerebrovascular occlusion. The data were classified using random forest, a machine learning algorithm. RESULTS: The top 10 metabolites identified from the random forest analysis were of the glycerophospholipid species and fatty acids. CONCLUSION: Preliminary analysis demonstrates feasibility of identification of lipid metabolomic profiling in cerebral thrombi retrieved from AIS patients. Recent advances in omic methodologies enable lipidomic profiling, which may provide insight into the cellular metabolic pathophysiology caused by AIS. Understanding of lipidomic changes in AIS may illuminate specific metabolite and lipid pathways involved and further the potential to develop personalized preventive strategies.

Association between thrombus composition and stroke etiology in the MR CLEAN Registry biobank

PURPOSE

The composition of thrombi retrieved during endovascular thrombectomy (EVT) in acute ischemic stroke (AIS) due to large vessel occlusion (LVO) may differ depending on their origin. In this study, we investigated the association between thrombus composition and stroke etiology in a large population of patients from the Dutch MR CLEAN Registry treated with EVT in daily clinical practice.

METHODS

The thrombi of 332 patients with AIS were histologically analyzed for red blood cells (RBC), fibrin/platelets (F/P), and white blood cells (leukocytes) using a machine learning algorithm. Stroke etiology was assessed using the Trial of Org 10,172 in acute stroke treatment (TOAST) classification.

RESULTS

The thrombi of cardioembolic origin contained less RBC and more F/P than those of non-cardioembolic origin (25.8% vs 41.2% RBC [p = 0.003] and 67.1% vs 54.5% F/P [p = 0.004]). The likelihood of a non-cardioembolic source of stroke increased with increasing thrombus RBC content (OR 1.02; [95% CI 1.00-1.06] for each percent increase) and decreased with a higher F/P content (OR 1.02; [95% CI 1.00-1.06]). Thrombus composition in patients with a cardioembolic origin and undetermined origin was similar.

CONCLUSION

Thrombus composition is significantly associated with stroke etiology, with an increase in RBC and a decrease in F/P raising the odds for a non-cardioembolic cause. No difference between composition of cardioembolic thrombi and of undetermined origin was seen. This emphasizes the need for more extensive monitoring for arrhythmias and/or extended cardiac analysis in case of an undetermined origin.

Correlation between Thrombus Perviousness and Distal Embolization during Mechanical Thrombectomy in Acute Stroke

PURPOSE

Thrombus permeability has been related to clot composition and treatment outcomes in stroke patients undergoing reperfusion therapies. The aim of this study was to evaluate whether thrombus perviousness, evaluated by multiphase computed tomography angiography (mCTA), is associated with distal embolization risk.

METHODS

We interrogated our dataset of acute ischemic stroke (AIS) patients involving the M1 segment of the middle cerebral artery (MCA) who had undergone mechanical thrombectomy, and we calculated thrombus average attenuation measurement (dHU) on non-contrast CT (NCCT) and clot perviousness on mCTA. dHU was calculated as the difference between the thrombus HU average value (tHU) and the HU average value on the contralateral side (cHU), while perviousness was calculated as the difference in mean clot density on mCTA and NCCT both in arterial (Perviousness pre-post-1) and delayed (Perviousness pre-post 2) phases.

RESULTS

A total of 100 patients (53 females (53%), mean age 72.74 [± 2.31]) with M1 occlusion were available for analysis. Perviousness, calculated between baseline and arterial phase of mCTA (Perviousness pre-post1), was lower in patients with distal embolization (p = 0.05), revealing an association between reduced perviousness and distal embolization risk. Logistic regression showed that thrombus perviousness calculated on the arterial phase of mCTA (OR, 0.66; 95% CI, 0.44-0.99] (p = 0.04)) and the contact aspiration technique (OR, 0.39; 95% CI, 0.15-1.02] (p = 0.05)) were protecting factors against distal embolization.

CONCLUSION

Our study showed an association between reduced perviousness and distal embolization, suggesting that perviousness evaluation may be a useful neuroimaging biomarker in predicting distal embolization risk during mechanical thrombectomy.

Absence of susceptibility vessel sign and hyperdense vessel sign in patients with cancer-related stroke

Background and aim

Identification of paraneoplastic hypercoagulability in stroke patients helps to guide investigations and prevent stroke recurrence. A previous study demonstrated an association between the absence of the susceptibility vessel sign (SVS) on brain MRI and active cancer in patients treated with mechanical thrombectomy. The present study aimed to confirm this finding and assess an association between the absence of the hyperdense vessel sign (HVS) on head CT and active cancer in all stroke patients.

Methods

SVS and HVS status on baseline imaging were retrospectively assessed in all consecutive stroke patients treated at a comprehensive stroke center between 2015 and 2020. Active cancer, known at the time of stroke or diagnosed within 1 year after stroke (occult cancer), was identified. Adjusted odds ratios (aOR) and their 95% confidence interval (CI) for the association between the thrombus imaging characteristics and cancer were calculated using multivariable logistic regression.

Results

Of the 2,256 patients with thrombus imaging characteristics available at baseline, 161 had an active cancer (7.1%), of which 36 were occult at the time of index stroke (1.6% of the total). The absence of SVS was associated with active cancer (aOR 3.14, 95% CI 1.45-6.80). No significance was reached for the subgroup of occult cancer (aOR 3.20, 95% CI 0.73-13.94). No association was found between the absence of HVS and active cancer (aOR 1.07, 95% CI 0.54-2.11).

Conclusion

The absence of SVS but not HVS could help to identify paraneoplastic hypercoagulability in stroke patients with active cancer and guide patient care.

Comparison of mechanical thrombectomy techniques in an in vitro stroke model: How to obtain a first pass recanalization?

BACKGROUND

Since mechanical thrombectomy (MT) has proven to be effective in the treatment of acute ischemic stroke (AIS), significant research has been dedicated to establishing procedural techniques offering best rate of first pass effect (FPE). In this study, we compared the efficacy of different techniques in vitro to achieve the first pass recanalisation (FPR).

METHODS

In vitro MT procedures were performed using a realistic silicone model of the human cerebral vasculature. The MT with stent retriever (SR) were performed with manual co-aspiration through the respective access catheter and intermediate catheter (IC), with Solumbra or partial retrieval techniques into the IC. Two SRs (Solitaire and EmboTrap) were selected to retrieve both red blood cells (RBC) rich and fibrin-rich clots. FPR rates were recorded for each case.

RESULTS

Overall, 144 MT were performed. FPR rates using the partial retrieval and Solumbra technique were of 100% and 87%, respectively (p = 0.01). The rate of FPR was of 92% using the balloon-guide catheter (BGC) compared to 64% with the guide catheter (GC) (p = 0.0001). With an IC, no differences were found between using a BGC or a GC (87.9% vs 89,6%, p = 0.75). No significant difference was observed between the Embotrap and the Solitaire device for the rate of FPR (82% and 74%, respectively; p = 0.23).

CONCLUSIONS

In this study, FPR rates were higher with the use of an IC associated with the partial retrieval technique, regardless the guide catheter, the SR, or the clot composition. The less effective technique was the association of GC and SR, without an IC.

Platelet-Neutrophil Association in NETs-Rich Areas in the Retrieved AIS Patient Thrombi

Histological structure of thrombi is a strong determinant of the outcome of vascular recanalization therapy, the only treatment option for acute ischemic stroke (AIS) patients. A total of 21 AIS patients from this study after undergoing non-enhanced CT scan and multimodal MRI were treated with mechanical stent-based and manual aspiration thrombectomy, and thromboembolic retrieved from a cerebral artery. Complementary histopathological and imaging analyses were performed to understand their composition with a specific focus on fibrin, von Willebrand factor, and neutrophil extracellular traps (NETs). Though distinct RBC-rich and platelet-rich areas were found, AIS patient thrombi were overwhelmingly platelet-rich, with 90% of thrombi containing <40% total RBC-rich contents (1.5 to 37%). Structurally, RBC-rich areas were simple, consisting of tightly packed RBCs in thin fibrin meshwork with sparsely populated nucleated cells and lacked any substantial von Willebrand factor (VWF). Platelet-rich areas were structurally more complex with thick fibrin meshwork associated with VWF. Plenty of leukocytes populated the platelet-rich areas, particularly in the periphery and border areas between platelet-rich and RBC-rich areas. Platelet-rich areas showed abundant activated neutrophils (myeloperoxidase+ and neutrophil-elastase+) containing citrullinated histone-decorated DNA. Citrullinated histone-decorated DNA also accumulated extracellularly, pointing to NETosis by the activated neutrophils. Notably, NETs-containing areas showed strong reactivity to VWF, platelets, and high-mobility group box 1 (HMGB1), signifying a close interplay between these components.

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.

Five material tissue decomposition by dual energy computed tomography

The separation of mixtures of substances into their individual components plays an important role in many areas of science. In medical imaging, one method is the established analysis using dual-energy computed tomography. However, when analyzing mixtures consisting of more than three individual basis materials, a physical limit is reached that no longer allows this standard analysis. In addition, the X-ray attenuation coefficients of chemically complicated basis materials may not be known and also cannot be determined by other or previous analyses. To address these issues, we developed a novel theoretical approach and algorithm and tested it on samples prepared in the laboratory as well as on ex-vivo medical samples. This method allowed both five-material decomposition and determination or optimization of the X-ray attenuation coefficients of the sample base materials via optimizations of objective functions. After implementation, this new multimodal method was successfully tested on self-mixed samples consisting of the aqueous base solutions iomeprol, eosin Y disodiumsalt, sodium chloride, and pure water. As a first proof of concept of this technique for detailed material decomposition in medicine we analyzed exact percentage composition of ex vivo clots from patients with acute ischemic stroke, using histological analysis as a reference standard.

Is Composition of Brain Clot Retrieved by Mechanical Thrombectomy Associated with Stroke Aetiology and Clinical Outcomes in Acute Ischemic Stroke?—A Systematic Review and Meta-Analysis

Background: Brain clots retrieved following endovascular thrombectomy in acute ischemic stroke patients may offer unique opportunities to characterise stroke aetiology and aid stroke decision-making in select groups of patients. However, the evidence around the putative association of clot morphology with stroke aetiology is limited and remains inconclusive. This study aims to perform a systematic review and meta-analysis to delineate the association of brain clot composition with stroke aetiology and post-reperfusion outcomes in patients receiving endovascular thrombectomy. Methods: The authors conducted a systematic literature review and meta-analysis by extracting data from several research databases (MEDLINE/PubMed, Cochrane, and Google Scholar) published since 2010. We used appropriate key search terms to identify clinical studies concerning stroke thrombus composition, aetiology, and clinical outcomes, in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Results: The authors identified 30 articles reporting on the relationship between stroke thrombus composition or morphology and aetiology, imaging, or clinical outcomes, of which 21 were included in the meta-analysis. The study found that strokes of cardioembolic origin (SMD = 0.388; 95% CI, 0.032–0.745) and cryptogenic origin (SMD = 0.468; 95% CI, 0.172–0.765) had significantly higher fibrin content than strokes of non-cardioembolic origin. Large artery atherosclerosis strokes had significantly lower fibrin content than cardioembolic (SMD = 0.552; 95% CI, 0.099–1.004) or cryptogenic (SMD = 0.455; 95% CI, 0.137–0.774) strokes. Greater red blood cell content was also significantly associated with a thrombolysis in cerebral infarction score of 2b–3 (SMD = 0.450; 95% CI, 0.177–0.722), and a positive hyperdense middle cerebral artery sign (SMD = 0.827; 95% CI, 0.472–1.183). No significant associations were found between red blood cell, platelet, or white blood cell content and aetiology, or between clot composition and bridging thrombolysis. Conclusions: This meta-analysis found that fibrin composition is significantly higher in strokes of cardioembolic and cryptogenic origin, and that red blood cell content is positively associated with the hyperdense middle cerebral artery sign and better reperfusion outcomes. Important advances to stroke clinical workup can be derived from these findings, in which many aspects of stroke workflow remain to be optimised. As data are still limited in terms of the association of various thrombus components with stroke aetiology as well as a standardised method of analysis, further studies are required to validate these findings to guide their use in clinical decision-making.

Novel synthetic clot analogs for in-vitro stroke modelling

Purpose

The increased demand for training of mechanical thrombectomy in ischemic stroke and development of new recanalization devices urges the creation of new simulation models both for training and device assessment. Clots properties have shown to play a role in procedural planning and thrombectomy device effectiveness. In this study, we analyzed the characteristics and applicability of completely synthetic, animal-free clots in the setting of an in-vitro model of mechanical thrombectomy for training and device assessment.

Methods

Synthetic clots based on agarose (n = 12) and silicone (n = 11) were evaluated in an in-vitro neurointervention simulation of mechanical thrombectomy with clot extraction devices. Calcified clots of mixed nature were simulated with addition of 3D printed structures. 9 clots were excluded due to insufficient vessel occlusion and failure to integrate with clot extraction device. Synthetic thrombi were characterized and compared using a categorical score-system on vessel occlusion, elasticity, fragmentation, adherence and device integration.

Results

Both agarose-based and silicone-based clots demonstrated relevant flow arrest and a good integration with the clot extraction device. Silicone-based clots scored higher on adherence to the vessel wall and elasticity.

Conclusion

Selected synthetic clots can successfully be implemented in an in-vitro training environment of mechanical thrombectomy. The clots’ different properties might serve to mimic fibrin-rich and red blood cell-rich human thrombi.

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.

Absence of Susceptibility Vessel Sign in Patients With Malignancy-Related Acute Ischemic Stroke Treated With Mechanical Thrombectomy

Background and Purpose

Clots rich in platelets and fibrin retrieved from patients with acute ischemic stroke (AIS) have been shown to be independently associated with the absence of the susceptibility vessel sign (SVS) on MRI and active malignancy. This study analyzed the association of SVS and the presence of active malignancy in patients with AIS who underwent mechanical thrombectomy (MT).

Methods

This single-center, retrospective, and cross-sectional study included consecutive patients with AIS with admission MRI treated with MT between January 2010 and December 2018. SVS status was evaluated on susceptibility-weighted imaging. Adjusted odds ratios (aORs) were calculated to determine the association between absent SVS and the presence of active or occult malignancy. The performance of predictive models incorporating and excluding SVS status was compared using areas under the receiver operating characteristics curve (auROC).

Results

Of 577 patients with AIS with assessable SVS status, 40 (6.9%) had a documented active malignancy and 72 (12.5%) showed no SVS. The absence of SVS was associated with active malignancy (aOR 4.85, 95% CI 1.94–12.11) or occult malignancy (aOR 11.42, 95% CI 2.36–55.20). The auROC of predictive models, including demographics and common malignancy biomarkers, was higher but not significant (0.85 vs. 0.81, p = 0.07) when SVS status was included.

Conclusion

Absence of SVS on admission MRI of patients with AIS undergoing MT is associated with malignancy, regardless of whether known or occult. Therefore, the SVS might be helpful in detecting paraneoplastic coagulation disorders and occult malignancy in patients with AIS.

CT Hyperdense Artery Sign and the Effect of Alteplase in Endovascular Thrombectomy after Acute Stroke

Background Recent evidence suggests that presence of an intracranial arterial thrombus with a hyperdense artery sign (HAS) at noncontrast CT (NCCT) is associated with better response to intravenous alteplase. Patients with HAS may benefit more from combined intravenous alteplase and endovascular treatment (EVT). Purpose To investigate whether HAS at NCCT modifies the treatment effect of adding intravenous alteplase on clinical outcome in patients with acute large-vessel occlusion undergoing EVT. Materials and Methods This study is a secondary analysis of a prospective randomized trial (Direct Intra-arterial thrombectomy in order to Revascularize AIS patients with large-vessel occlusion Efficiently in Chinese Tertiary hospitals: A Multicenter randomized clinical Trial [DIRECT-MT]), which compared adding alteplase to EVT versus EVT alone in participants with acute large-vessel occlusion between February 2018 and July 2019. Participants with catheter angiograms and adequate NCCT for HAS evaluation were included. HAS was determined visually by two independent investigators at baseline NCCT. Treatment effect of intravenous alteplase administration according to presence of HAS on the primary clinical outcome (modified Rankin Scale [mRS] score at 90 days) and secondary and safety outcomes were assessed using adjusted multivariable regression models. Results Among 633 included participants (356 men [56%]; median age, 69 years), HAS was observed in 283 participants (45%): 142 of 313 participants (45%) in the EVT-only group and 141 of 320 participants (44%) in the group with added intravenous alteplase. Treatment-by-HAS interaction was observed for the primary outcome (P < .001), whereby a shift in favor of better outcomes with added intravenous alteplase occurred in participants with HAS (adjusted odds ratio [OR]: 1.82; 95% CI: 1.18, 2.79), while an adverse effect was seen in participants without HAS (adjusted OR: 0.62; 95% CI: 0.42, 0.91). This also held true for three secondary outcomes (excellent outcome [mRS score of 0-1 at 90 days], P = .005; good outcome [mRS score of 0-2 at 90 days], P = .008; final successful reperfusion, P = .04) in the adjusted models. Conclusion After acute ischemic stroke, presence of hyperdense artery sign (HAS) at baseline noncontrast CT indicated better outcomes when alteplase was added to endovascular treatment, but adding alteplase to endovascular treatment resulted in worse outcomes in participants without HAS. Clinical trial registration no. NCT03469206 © RSNA, 2022 Online supplemental material is available for this article.

Contrast agent retention sign in angiography predicts acute internal carotid artery embolic occlusion

BACKGROUND

Identification of acute internal carotid artery embolism (ICAE) and internal carotid artery atherosclerotic stenosis (ICAAS) in acute ischemic stroke patients is important for selection of treatment. The presence of contrast agent retention on pre-procedural angiographic images is more common in patients with ICA occlusion caused by embolism compared to patients with ICA atherosclerotic stenosis. This study aimed to evaluate effectiveness of contrast agent retention sign for predicting ICAE.

METHODS

Sixty-five patients with ICA occlusion who underwent emergency endovascular treatment from September 2014 to September 2020 were included in this retrospective analysis. Patients were divided into ICAE (n = 46) and ICAAS (n = 19) groups. Clinical characteristics, imaging data and ICA contrast agent retention signs of patients were collected. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and diagnosis accuracy of contrast agent retention sign were conducted.

RESULTS

The positive ICA contrast agent retention sign was significantly more common in patients with ICAE (60.87% vs 0.00%, P < 0.001) than that of patients with ICAAS, but significantly lower in male patients (53.57% vs 81.08%, P = 0.017). There were significantly more patients with positive sign had occlusion in C6 segment (64.29% vs 13.51%, P < 0.001) and no outflow tract (85.71% vs 5.41%, P < 0.001) compared with negative sign group. There were significantly fewer patients with postive sign had occlusion in C1 segment (0.00% vs 40.54%, P < 0.001) compared with negative sign group. The sensitivity, specificity, PPV, NPV and diagnosis accuracy of contrast agent retention sign for predicting ICAE occlusion were 60.87%, 100%, 100%, 51.35% and 72.31%, respectively.

CONCLUSION

The ICA contrast agent retention sign has very high specificity and moderate sensitivity for detection of acute ICAE.

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.

Impact of histological clot composition on preprocedure imaging and mechanical thrombectomy

INTRODUCTION:

We studied the relationship of acute ischemic stroke (AIS) large-vessel occlusion clot composition with vessel recanalization and preprocedure imaging.

SUBJECTS AND METHODS:

Individual clots from AIS patients who underwent mechanical thrombectomy (MT) between September 2016 and September 2018 were examined. Clot composition was analyzed histologically through a trichrome staining and image segmentation, and the area occupied by red blood cells (RBCs), fibrin, or mixed composition was quantified.

RESULTS:

Forty-three patients (65.4 ± 12.7 years, 39% of females) who underwent 92 retrieval passes (mean 2.14, range 1–6) were included in this study. Fibrin (44%) occupied the greatest area, followed by mixed composition (34%) and RBCs (22%). A stent retriever was deployed in 81% of cases, 20 patients (47%) achieved first-pass efficacy (FPE) (thrombolysis in cerebral infarction [TICI] 2b-3 after first pass), 41 (95%) achieved successful revascularization (TICI 2b-3), and 21 (49%) had good outcome (modified Rankin Scale [mRS] ≤2) at 90 days. Hyperdense artery sign (HAS) on initial computed tomography was correlated with mixed clot composition (P = 0.01) and lack of fibrin content (P = 0.03). In the univariate analysis, FPE was associated with RBC clot area, atrial fibrillation, and occlusion location but not with fibrin clot area, mixed clot area, stroke etiology, thrombectomy technique, distal emboli, or 90-day mRS. In the multivariate analysis, FPE was significantly correlated with low RBC clot area (odd ratio = 0.96, confidence interval [0.92.99], P = 0.034) but not with atrial fibrillation or location.

CONCLUSION:

Our results suggest that HAS is correlated with mixed clot composition and lower fibrin content and that lower RBC clot composition is associated with FPE in patients undergoing MT.

Association of Stroke Subtype With Hemorrhagic Transformation Mediated by Thrombectomy Pass: Data From the ANGEL-ACT Registry

BACKGROUND

The role of stroke etiology subtype in patients with acute large vessel occlusion on the occurrence of hemorrhagic transformation (HT) after endovascular treatment is poorly studied, and which factors mediate their relationship remains largely unknown. We utilized nationwide registry data to explore the association of stroke subtype (cardioembolism versus large artery atherosclerosis) with HT and to identify the possible mediators.

METHODS

A total of 1015 subjects were selected from the ANGEL-ACT registry (Endovascular Treatment Key Technique and Emergency Work Flow Improvement of Acute Ischemic Stroke)-a prospective consecutive cohort of acute large vessel occlusion patients undergoing endovascular treatment at 111 hospitals in China between November 2017 and March 2019-and divided into large artery atherosclerosis (n=538) and cardioembolism (n=477) according to the Trial of ORG 10172 in Acute Stroke Treatment criteria. The types of HT included any intracerebral hemorrhage (ICH), parenchymal hematoma, and symptomatic ICH within 24 hours after endovascular treatment. The association between stroke subtype and HT was analyzed using a logistic regression model. Mediation analysis was done to assess how much of the effect of stroke subtype on HT was mediated through the identified mediators.

RESULTS

Stroke subtype (cardioembolism versus large artery atherosclerosis) was associated with increased risk of any ICH (29.8% versus 16.5%; odds ratio, 2.03 [95% CI, 1.22-3.36]), parenchymal hematoma (14.3% versus 5.4%; odds ratio, 2.90 [95% CI, 1.38-6.13]), and symptomatic ICH (9.9% versus 4.7%; odds ratio, 2.59 [95% CI, 1.09-6.16]) after adjustment for potential confounders. The more thrombectomy passes in cardioembolism patients had a significant mediation effect on the association of stroke subtype with increased risk of HT (any ICH, 15.9%; parenchymal hematoma, 13.4%; symptomatic ICH, 14.2%, respectively).

CONCLUSIONS

Stroke subtype is an independent risk factor for HT within 24 hours following endovascular treatment among acute large vessel occlusion patients. Mediation analyses propose that stroke subtype contributes to HT partly through thrombectomy pass, suggesting a possible pathomechanistic link.

Characterising acute ischaemic stroke thrombi: insights from histology, imaging and emerging impedance-based technologies

Treatment of acute ischaemic stroke (AIS) focuses on rapid recanalisation of the occluded artery. In recent years, advent of mechanical thrombectomy devices and new procedures have accelerated the analysis of thrombi retrieved during the endovascular thrombectomy procedure. Despite ongoing developments and progress in AIS imaging techniques, it is not yet possible to conclude definitively regarding thrombus characteristics that could advise on the probable efficacy of thrombolysis or thrombectomy in advance of treatment. Intraprocedural devices with dignostic capabilities or new clinical imaging approaches are needed for better treatment of AIS patients. In this review, what is known about the composition of the thrombi that cause strokes and the evidence that thrombus composition has an impact on success of acute stroke treatment has been examined. This review also discusses the evidence that AIS thrombus composition varies with aetiology, questioning if suspected aetiology could be a useful indicator to stroke physicians to help decide the best acute course of treatment. Furthermore, this review discusses the evidence that current widely used radiological imaging tools can predict thrombus composition. Further use of new emerging technologies based on bioimpedance, as imaging modalities for diagnosing AIS and new medical device tools for detecting thrombus composition in situ has been introduced. Whether bioimpedance would be beneficial for gaining new insights into in situ thrombus composition that could guide choice of optimum treatment approach is also reviewed.

A fibrin targeted molecular imaging evaluation of microvascular no-reflow in acute ischemic stroke

OBJECTIVE

To investigate the relationship between fibrin deposition and "no-reflow" within microcirculation after thrombolysis in acute ischemic stroke (AIS).

MATERIALS AND METHODS

Experiments were approved by the institutional animal care and use committee. An experimental AIS model was induced in C57BL/6 mice by middle cerebral artery occlusion (MCAO) via the photothrombotic method. Mice were randomly assigned to non-thrombolytic or thrombolytic treated groups (n = 12 per group). The modified Neurological Severity Score and Fast Beam Balance Test were performed by a researcher blinded to the treatment method. MRI was utilized to evaluate all of the mice. An FXIIIa-targeted probe was applied to detect fibrin deposition in acute ischemic brain regions by fluorescence imaging. Necrosis and pathological changes of brain tissue were estimated via Hematoxylin and eosin staining while fibrin deposition was observed by immunohistochemistry.

RESULTS

Thrombolytic therapy improved AIS clinical symptoms. The infarct area of non-thrombolytic treated mice was significantly greater than that of the thrombolytic treated mice (p < .0001). Fluorescent imaging indicated fibrin deposition in ischemic brain tissue in both groups, with less fibrin in non-thrombolytic treated mice than thrombolytic treated mice, though the difference was not significant. Brain cells with abnormal morphology, necrosis, and liquefication were observed in the infarcted area for both groups. Clotted red blood cells (RBCs) and fibrin build-up in capillaries were found near the ischemic area in both non-thrombolytic and thrombolytic treated groups of mice.

CONCLUSION

Fibrin deposition and stacked RBCs contribute to microcirculation no-reflow in AIS after thrombolytic therapy.

What is the added value of CT-angiography in patients with transient ischemic attack?

Background

Transient ischemic attack (TIA) is an important predictor for a pending stroke. Guidelines recommend a workup for TIA-patients similar to that of stroke patients, including an assessment of the extra- and intracranial arteries for vascular pathologies with direct therapeutic implications via computed tomography angiography (CTA). Aim of our study was a systematic analysis of TIA-patients receiving early CTA-imaging and to evaluate the predictive value of TIA-scores and clinical characteristics for ipsilateral vascular pathologies and the need of an invasive treatment.

Methods

We analysed clinical and imaging data from TIA patients being admitted to a tertiary university hospital between September 2015 and March 2018. Following subgroups were identified: 1) no- or low-grade vascular pathology 2) ipsilateral high-risk vascular pathology and 3) high-risk findings that needed invasive, surgical or interventional treatment. We investigated established TIA-scores (ABCD₂-, the ABCD₃- and the SPI-II score) and various clinical characteristics as predictive factors for ipsilateral vascular pathologies and the need for invasive treatment.

Results

Of 812 patients, 531 (65.4%) underwent initial CTA in the emergency department. In 121 (22.8%) patients, ipsilateral vascular pathologies were identified, of which 36 (6.7%) needed invasive treatment. The ABCD₂-, ABCD₃- and SPI-II-scores were not predictive for ipsilateral vascular pathologies or the need for invasive treatment. We identified male sex (OR 1.579, 95%CI 1.049–2.377, p = 0.029), a short duration of symptoms (OR 0.692, 95% CI 0.542–0.884, p = 0.003), arterial hypertension (OR 1.718, 95%CI 0.951–3.104, p = 0.073) and coronary heart disease (OR 1.916, 95%CI 1.184–3.101, p = 0.008) as predictors for ipsilateral vascular pathologies. As predictors for the need of invasive treatment, a short duration of symptoms (OR 0.565, 95%CI 0.378–0.846, p = 0.006), arterial hypertension (OR 2.612, 95%OR 0.895–7.621, p = 0.079) and hyperlipidaemia (OR 5.681, 95%CI 0.766–42.117, p = 0.089) as well as the absence of atrial fibrillation (OR 0.274, OR 0.082–0.917, p = 0.036) were identified.

Conclusion

More than every fifth TIA-patient had relevant vascular findings revealed by acute CTA. TIA-scores were not predictive for these findings. Patients with a short duration of symptoms and a vascular risk profile including coronary heart disease, arterial hypertension and hyperlipidaemia most likely might benefit from early CTA to streamline further diagnostics and therapy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12883-021-02523-y.

Association of thrombus density and endovascular treatment outcomes in patients with acute ischemic stroke due to M1 occlusions

PURPOSE

We aimed to study the association of non-contrast CT (NCCT) thrombus density with procedural and clinical outcomes in patients with acute ischemic stroke who underwent endovascular treatment (EVT). Since thrombus density is associated with thrombus location, we focused on M1 occlusions only.

METHODS

Patients with available thin-slice (< 2.5 mm) NCCT were included from a nationwide registry. Regression models were used to assess the relation between thrombus density (per Hounsfield unit [HU]) and the following outcomes. For reperfusion grade, adjusted common odds ratios (acOR) indicated a 1-step shift towards improved outcome per HU increase in thrombus density. For the binary outcomes of first-pass reperfusion (first-pass extended thrombolysis in cerebral infarction [eTICI] 2C-3, FPR), functional independence [90-day modified Rankin Scale (mRS) score of 0-2] and mortality), aORs were reported. Adjusted β coefficients (aβ) were reported for 24-h NIHSS and procedure duration in minutes. Outcome differences between first-line treatment devices (stent retriever versus aspiration) were assessed with interaction terms.

RESULTS

In 566 patients with M1 occlusions, thrombus density was not associated with reperfusion (acOR 1.01, 95% CI 0.99-1.02), FPR (aOR 1.01, 95% CI 0.99-1.03), mortality (aOR 0.98, 95% CI 0.95-1.00), 24-h NIHSS (aβ - 0.7%, 95% CI - 1.4-0.2), or procedure duration (aβ 0.27, 95% CI - 0.05-0.58). In multivariable analysis, thrombus density was associated with functional independence (aOR 1.02, 95% CI 1.00-1.05). No interaction was found between thrombus density and first-line treatment device for any outcome.

CONCLUSION

In patients with M1 occlusions, thrombus density was not clearly associated with procedural and clinical outcomes after EVT.

Quantitative thrombus characteristics on thin-slice computed tomography improve prediction of thrombus histopathology: results of the MR CLEAN Registry

OBJECTIVES

Thrombus computed tomography (CT) characteristics might be used to assess histopathologic thrombus composition in patients treated with endovascular thrombectomy (EVT) for acute ischemic stroke (AIS). We aimed to assess the variability in thrombus composition that could be predicted with combined thrombus CT characteristics.

METHODS

Thrombi of patients enrolled in the MR CLEAN Registry between March 2014 and June 2016 were histologically analyzed with hematoxylin-eosin staining and quantified for percentages of red blood cells (RBCs) and fibrin/platelets. We estimated the association between general qualitative characteristics (hyperdense artery sign [HAS], occlusion location, clot burden score [CBS]) and thrombus composition with linear regression, and quantified RBC variability that could be explained with individual and combined characteristics with R². For patients with available thin-slice (≤ 2.5 mm) imaging, we performed similar analyses for general and quantitative characteristics (HAS, occlusion location, CBS, [relative] thrombus density, thrombus length, perviousness, distance from ICA-terminus).

RESULTS

In 332 included patients, the presence of HAS (aβ 7.8 [95% CI 3.9-11.7]) and shift towards a more proximal occlusion location (aβ 3.9 [95% CI 0.6-7.1]) were independently associated with increased RBC and decreased fibrin/platelet content. With general characteristics, 12% of RBC variability could be explained; HAS was the strongest predictor. In 94 patients with available thin-slice imaging, 30% of RBC variability could be explained; thrombus density and thrombus length were the strongest predictors.

CONCLUSIONS

Quantitative thrombus CT characteristics on thin-slice admission CT improve prediction of thrombus composition and might be used to further guide clinical decision-making in patients treated with EVT for AIS in the future.

KEY POINTS

• With hyperdense artery sign and occlusion location, 12% of variability in thrombus RBC content can be explained. • With hyperdense artery sign, occlusion location, and quantitative thrombus characteristics on thin-slice (≤ 2.5 mm) non-contrast CT and CTA, 30% of variability in thrombus RBC content can be explained. • Absolute thrombus density and thrombus length were the strongest predictors for thrombus composition.

A review on the association of thrombus composition with mechanical and radiological imaging characteristics in acute ischemic stroke

Thrombus composition and mechanical properties significantly impact the ease and outcomes of thrombectomy procedures in patients with acute ischemic stroke. A wide variation exists in the composition of thrombi between patients. If a relationship can be determined between the composition of a thrombus and its mechanical behaviour, as well as between the composition of a thrombus and its radiological imaging characteristics, then there is the potential to personalise thrombectomy treatment based on each individual thrombus. This review aims to give an overview of the current literature addressing this issue. Here, we present a scoping review detailing associations between thrombus composition, mechanical behaviour and radiological imaging characteristics. We conducted two searches 1) on the association between thrombus composition and the mechanical behaviour of the tissue and 2) on the association between radiological imaging characteristics and thrombus composition in the acute stroke setting. The review suggests that higher fibrin and lower red blood cell (RBC) content contribute to stiffer thrombi independent of the loading mode. Further, platelet-contracted thrombi are stiffer than non-contracted compositional counterparts. Fibrin content contributes to the elastic portion of viscoelastic behaviour while RBC content contributes to the viscous portion. It is possible to identify fibrin-rich or RBC-rich thrombi with computed tomography and magnetic resonance imaging vessel signs. Standardisation is required to quantify the association between thrombus density on non-contrast computed tomography and the RBC content. The characterisation of the thrombus fibrin network has not been addressed so far in radiological imaging but may be essential for the prediction of device-tissue interactions and distal thrombus embolization. The association between platelet-driven clot contraction and radiological imaging characteristics has not been explicitly investigated. However, evidence suggests that perviousness may be a marker of clot contraction.

Thrombus Histology as It Relates to Mechanical Thrombectomy: A Meta-Analysis and Systematic Review

BACKGROUND

Appropriate thrombus-device interaction is critical for recanalization. Histology can serve as a proxy for mechanical properties, and thus inform technique selection.

OBJECTIVE

To investigate the value of histologic characterization, we conducted a systematic review and meta-analysis on the relationship between thrombus histology and recanalization, technique, etiology, procedural efficiency, and imaging findings.

METHODS

In this meta-analysis, we identified studies published between March 2010 and March 2020 reporting findings related to the histologic composition of thrombi in large vessel occlusion stroke. Studies with at least 10 patients who underwent mechanical thrombectomy using stent retriever or aspiration were considered. Only studies in which retrieved thrombi were histologically processed were included. Patient-level data were requested when data could not be directly extracted. The primary outcome assessed was the relationship between thrombus histology and angiographic outcome.

RESULTS

A total of 22 studies encompassing 1623 patients met inclusion criteria. Clots associated with good angiographic outcome had higher red blood cell (RBC) content (mean difference [MD] 9.60%, 95% CI 3.85-15.34, P = .008). Thrombi retrieved by aspiration had less fibrin (MD -11.39, 95% CI -22.50 to -0.27, P = .046) than stent-retrieved thrombi. Fibrin/platelet-rich clots were associated with longer procedure times (MD 13.20, 95% CI 1.30-25.10, P = .037). Hyperdense artery sign was associated with higher RBC content (MD 14.17%, 95% CI 3.07-25.27, P = .027). No relationship was found between composition and etiology.

CONCLUSION

RBC-rich thrombi were associated with better recanalization outcomes and shorter procedure times, suggesting that preinterventional compositional characterization may yield important prognostic and therapeutic guidance.

Thrombus Composition, Imaging, and Outcome Prediction in Acute Ischemic Stroke

BACKGROUND AND OBJECTIVES

New imaging techniques have advanced our ability to capture thrombus characteristics and burden in real time. An improved understanding of recanalization rates with thrombolysis and endovascular thrombectomy based on thrombus characteristics has spurred interest in new therapies for acute stroke.

METHODS AND RESULTS

This article reviews the biochemical, structural, and imaging characteristics of intracranial thrombi in acute ischemic stroke; the relationship between thrombus composition and response to lytic and endovascular therapies; and current and future directions for improving outcomes in patients with acute stroke based on thrombus characteristics.

DISCUSSION

Thrombus composition, size, location, and timing from stroke onset correlate with imaging findings in acute ischemic stroke and are associated with clinical outcome. Further research across multiple domains could assist in better applying our knowledge of thrombi to patient selection and individualization of acute therapies.

Studying Stroke Thrombus Composition After Thrombectomy: What Can We Learn?

The composition of ischemic stroke thrombi has gained an increasing amount of interest in recent years. The implementation of endovascular procedures in standard stroke care has granted researchers the unique opportunity to examine patient thrombus material. Increasing evidence indicates that stroke thrombi are complex and heterogenous, consisting of various biochemical (eg, fibrin, von Willebrand Factor, and neutrophil extracellular traps) and cellular (eg, red blood cells, platelets, leukocytes, and bacteria) components. This complex composition may explain therapeutic limitations and also offer novel insights in several aspects of stroke management. Better understanding of thrombus characteristics could, therefore, potentially lead to improvements in the management of patients with stroke. In this review, we provide a comprehensive overview of the lessons learned by examining stroke thrombus composition after endovascular thrombectomy and its potential relevance for thrombectomy success rates, thrombolysis, clinical outcomes, stroke etiology, and radiological imaging.

Characterization of the 'White' Appearing Clots that Cause Acute Ischemic Stroke

OBJECTIVES

Most clots retrieved from patients with acute ischemic stroke are 'red' in color. 'White' clots represent a less common entity and their histological composition is less known. Our aim was to investigate the composition, imaging and procedural characteristics of 'white' clots retrieved by mechanical thrombectomy.

MATERIALS AND METHODS

Seventy five 'white' thrombi were selected by visual inspection from a cohort of 760 clots collected as part of the RESTORE registry. Clots were evaluated histopathologically.

RESULTS

Quantification of Martius Scarlett Blue stain identified platelets/other as the major component in 'white' clots' (mean of 55% of clot overall composition) followed by fibrin (31%), red blood cells (6%) and white blood cells (3%). 'White' clots contained significantly more platelets/other (p<0.001*) and collagen/calcification (p<0.001*) and less red blood cells (p<0.001*) and white blood cells (p=0.018*) than 'red' clots. The mean platelet and von Willebrand Factor expression was 43% and 24%, respectively. Adipocytes were found in four cases. 'White' clots were significantly smaller (p=0.016*), less hyperdense (p=0.005*) on computed tomography angiography/non-contrast CT and were associated with a smaller extracted clot area (p<0.001*) than 'red' clots. They primarily caused the occlusion of middle cerebral artery, were less likely to be removed by aspiration and more likely to require rescue-therapy for retrieval.

CONCLUSIONS

'White' clots represented 14% of our cohort and were platelet, von Willebrand Factor and collagen/calcification-rich. 'White' clots were smaller, less hyperdense, were associated with significantly more distal occlusions and were less successfully removed by aspiration alone than 'red' clots.

Development and reliability of the histological THROMBEX-classification rule for thrombotic emboli of acute ischemic stroke patients

Background

Thrombus histology has become a potential diagnostic tool for the etiology assessment of patients with ischemic stroke caused by embolic proximal vessel occlusion. We validated a classification rule that differentiates between cardiac and arteriosclerotic emboli in individual stroke patients. We aim to describe in detail the development of this classification rule and disclose its reliability.

Methods

The classification rule is based on the hypothesis that cardiac emboli arise out of separation thrombi and arteriosclerotic emboli result from agglutinative thrombi. 125 emboli recovered by thrombectomy from stroke patients and 11 thrombi serving as references for cardiac (n = 5) and arteriosclerotic emboli (n = 6) were Hematoxylin and eosin, Elastica-van Gieson and CD61 stained and rated independently by two histopathologists blinded to the presumed etiology by several pre-defined criteria. Intra- and interobserver reliabilities of all criteria were determined. Out of the different criteria, three criteria with the most satisfactory reliability values were selected to compose the classification rule that was finally adjusted to the reference thrombi. Reliabilities of the classification rule were calculated by using the emboli of stroke patients.

Results

The classification rule reached intraobserver reliabilities for the two raters of 92.9% and 68.2%, respectively. Interobserver reliability was 69.9%.

Conclusions

A new classification rule for emboli obtained from thrombectomy was established. Within the limitations of histological investigations, it is reliable and able to distinguish between cardioembolic and arteriosclerotic emboli.

Supplementary Information

The online version contains supplementary material available at 10.1186/s42466-021-00149-6.

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

Mechanical thrombectomy renders the occluding clot available for analysis. Insights into thrombus composition could help establish the stroke cause. We aimed to investigate the value of clot composition analysis as a complementary diagnostic tool in determining the etiology of large vessel occlusion (LVO) ischemic strokes (International Prospective Register of Systematic Reviews [PROSPERO] registration # CRD42020199436). Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we ran searches on Medline (using the PubMed interface) and Web of Science for studies reporting analyses of thrombi retrieved from LVO stroke patients subjected to mechanical thrombectomy (January 1, 2006 to September 21, 2020). The PubMed search was updated weekly up to February 22, 2021. Reference lists of included studies and relevant reviews were hand-searched. From 1,714 identified studies, 134 eligible studies (97 cohort studies, 31 case reports, and six case series) were included in the qualitative synthesis. Physical, histopathological, biological, and microbiological analyses provided information about the gross appearance, mechanical properties, structure, and composition of the thrombi. There were non-unanimous associations of thrombus size, structure, and composition (mainly proportions of fibrin and blood formed elements) with the Trial of Org 10172 in Acute Stroke Treatment (TOAST) etiology and underlying pathologies, and similarities between cryptogenic thrombi and those of known TOAST etiology. Individual thrombus analysis contributed to the diagnosis, mainly in atypical cases. Although cohort studies report an abundance of quantitative rates of main thrombus components, a definite clot signature for accurate diagnosis of stroke etiology is still lacking. Nevertheless, the qualitative examination of the embolus remains an invaluable tool for diagnosing individual cases, particularly regarding atypical stroke causes.

Radiology-Pathology Correlations of Intracranial Clots: Current Theories, Clinical Applications, and Future Directions

In recent years, there has been substantial progression in the field of stroke clot/thrombus imaging. Thrombus imaging aims to deduce the histologic composition of the clot through evaluation of various imaging characteristics. If the histology of a thrombus can be reliably determined by noninvasive imaging methods, critical information may be extrapolated about its expected response to treatment and about the patient's clinical outcome. Crucially, as we move into an era of stroke therapy individualization, determination of the histologic composition of a clot may be able to guide precise and targeted therapeutic effort. Most radiologists, however, remain largely unfamiliar with the topic of clot imaging. This article will review the current literature regarding clot imaging, including its histologic backdrop, the correlation of images with cellular components and treatment responsiveness, and future expectations.

Carotid webs in large vessel occlusion stroke: Clinical, radiological and thrombus histopathological findings

BACKGROUND

Carotid webs are an under-recognized embolic source in patients with cryptogenic stroke. Limited resources currently exist to assist clinicians in stroke prevention for patients with symptomatic carotid webs (SCW). We aimed at analysing the clinical, radiological and procedural features of stroke patients with SCW undergoing endovascular thrombectomy (EVT), and to describe the histopathological composition of their occlusive thrombi.

METHODS

In a single-center observational study on consecutive patients with ischemic stroke treated by EVT, carotid web was defined symptomatic when it was ipsilateral to the ischemic lesion in a patient classified with stroke of otherwise undetermined etiology. Clinical, radiological and procedural data of patients with SCW were evaluated. Histopathological examination of the retrieved thrombi was performed.

RESULTS

Out of 1430 patients with large vessel occlusion stroke treated by EVT, 11(0.7%) were found to have a SCW. Patients with SCW had a median age of 47 years old (IQR 38-50), they were prevalently women (55%), mostly of African ethnicity (91%). Each of the 11 patients achieved successful angiographic reperfusion (mTICI 2b-3) after EVT. For secondary prevention, elective endovascular carotid stenting was performed in 5 (55%) patients, while 1 (9%) was treated by surgical endoarterectomy. Histological analysis of the retrieved thrombi performed in 4 patients showed a mixed composition with variable red blood cell content.

CONCLUSIONS

EVT is feasible in large vessel occlusion stroke related to SCW. Procedures of carotid revascularization appear to be feasible therapeutic options for secondary prevention. The histopathological analysis of cerebral thrombi may provide new insights on stroke pathogenesis in patients with SCW.

An Older Thrombus Delays Reperfusion after Mechanical Thrombectomy for Ischemic Stroke

Background  Thrombosis is a dynamic process, and a thrombus undergoes physical and biochemical changes that may alter its response to reperfusion therapy. This study assessed whether thrombus age influenced reperfusion quality and outcomes after mechanical thrombectomy for cerebral embolism.

Methods  We retrospectively evaluated 185 stroke patients and thrombi that were collected during mechanical thrombectomy at three stroke centers. Thrombi were pathologically classified as fresh or older based on their granulocytes' nuclear morphology and organization. Thrombus components were quantified, and the extent of NETosis (the process of neutrophil extracellular trap formation) was assessed using the density of citrullinated histone H3-positive cells. Baseline patient characteristics, thrombus features, endovascular procedures, and functional outcomes were compared according to thrombus age.

Results  Fresh thrombi were acquired from 43 patients, and older thrombi were acquired from 142 patients. Older thrombi had a lower erythrocyte content ( p  < 0.001) and higher extent of NETosis ( p  = 0.006). Restricted mean survival time analysis revealed that older thrombi were associated with longer puncture-to-reperfusion times (difference: 15.6 minutes longer for older thrombi, p  = 0.002). This association remained significant even after adjustment for erythrocyte content and the extent of NETosis (adjusted difference: 10.8 minutes, 95% confidence interval [CI]: 0.6–21.1 minutes, p  = 0.039). Compared with fresh thrombi, older thrombi required more device passes before reperfusion ( p  < 0.001) and were associated with poorer functional outcomes (adjusted common odds ratio: 0.49; 95% CI: 0.24–0.99).

Conclusion  An older thrombus delays reperfusion after mechanical thrombectomy for ischemic stroke. Adding therapies targeting thrombus maturation may improve the efficacy of mechanical thrombectomy.