The Role of von Willebrand Factor, ADAMTS13, and Cerebral Artery Thrombus Composition in Patient Outcome Following Mechanical Thrombectomy for Acute Ischemic Stroke

Acute Ischemic Stroke Thrombus Composition

Ischemic stroke is caused by a thrombus blocking one or multiple arteries in the brain, resulting in irreversible damage in the associated brain tissue. The aim of therapy is to restore the blood flow as fast as possible. Two recanalization strategies are currently available: pharmacological thrombolysis using recombinant tissue plasminogen activator (rt-PA) and mechanical removal of the thrombus. Despite recent advancements, achieving efficient recanalization remains a challenge. The precise causes of therapy failure are not fully understood but thrombus composition is likely a key factor in successful recanalization. This review explores acute ischemic stroke thrombus composition, its recently identified components, and how it affects stroke treatment. It also discusses how new insights could enhance current recanalization strategies for ischemic stroke patients.

What is a Challenging Clot? : A DELPHI Consensus Statement from the CLOTS 7.0 Summit

BACKGROUND

Predicting a challenging clot when performing mechanical thrombectomy in acute stroke can be difficult. One reason for this difficulty is a lack of agreement on how to precisely define these clots. We explored the opinions of stroke thrombectomy and clot research experts regarding challenging clots, defined as difficult to recanalize clots by endovascular approaches, and clot/patient features that may be indicative of such clots.

METHODS

A modified DELPHI technique was used before and during the CLOTS 7.0 Summit, which included experts in thrombectomy and clot research from different specialties. The first round included open-ended questions and the second and final rounds each consisted of 30 closed-ended questions, 29 on various clinical and clot features, and 1 on number of passes before switching techniques. Consensus was defined as agreement ≥ 50%. Features with consensus and rated ≥ 3 out of 4 on the certainty scale were included in the definition of a challenging clot.

RESULTS

Three DELPHI rounds were performed. Panelists achieved consensus on 16/30 questions, of which 8 were rated 3 or 4 on the certainty scale, namely white-colored clots (mean certainty score 3.1), calcified clots under histology (3.7) and imaging (3.7), stiff clots (3.0), sticky/adherent clots (3.1), hard clots (3.1), difficult to pass clots (3.1) and clots that are resistant to pulling (3.0). Most panelists considered switching endovascular treatment (EVT) techniques after 2-3 unsuccessful attempts.

CONCLUSION

This DELPHI consensus identified 8 distinct features of a challenging clot. The varying degree of certainty amongst the panelists emphasizes the need for more pragmatic studies to enable accurate a priori identification of such occlusions prior to EVT.

The thrombus proteome in stroke reveals a key role of the innate immune system and new insights associated with its etiology, severity, and prognosis

BACKGROUND

Nowadays little is known about the molecular profile of the occluding thrombus of patients with ischemic stroke.

OBJECTIVES

To analyze the proteomic profile of thrombi in patients who experienced an ischemic stroke in order to gain insights into disease pathogenesis.

METHODS

Thrombi from an exploratory cohort of patients who experienced a stroke were obtained by thrombectomy and analyzed by sequential window acquisition of all theoretical spectra-mass spectrometry. Unsupervised k-means clustering analysis was performed to stratify patients who experienced a stroke. The proteomic profile was associated with both the neurological function (National Institute of Health Stroke Scale [NIHSS]) and the cerebral involvement (Alberta Stroke Program Early CT Score [ASPECTS]) prior to thrombectomy and the clinical status of patients at 3 months using the modified Rankin Scale. In an independent cohort of 210 patients who experienced a stroke, the potential role of neutrophils in stroke severity was interrogated.

RESULTS

Proteomic analysis identified 580 proteins in thrombi, which were stratified into 4 groups: hemostasis, proteasome and neurological diseases, structural proteins, and innate immune system and neutrophils. The thrombus proteome identified 3 clusters of patients with distinctive severity, prognosis, and etiology of the stroke. A protein signature clearly distinguished atherothrombotic and cardioembolic strokes. Several proteins were significantly correlated with the severity of the stroke (NIHSS and ASPECTS). Functional proteomic analysis highlighted the prominent role of neutrophils in stroke severity. This was in line with the association of neutrophil activation markers and count with NIHSS, ASPECTS, and the modified Rankin Scale score 90 days after the event.

CONCLUSION

The use of sequential window acquisition of all theoretical spectra-mass spectrometry in thrombi from patients who experienced an ischemic stroke has provided new insights into pathways and players involved in its etiology, severity, and prognosis. The prominent role of the innate immune system identified might pave the way for the development of new biomarkers and therapeutic approaches in this disease.

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.

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.

Immediate outcome prognostic value of plasma factors in patients with acute ischemic stroke after intravenous thrombolytic treatment

In the present study, we explored multiple plasma factors to predict the outcomes of patients with AIS after IVT. Fifty AIS patients who received IVT with alteplase were recruited and divided into two groups according to their NIHSS scores. Serum from all subjects was collected to quantitatively analyze the levels of different plasma factors, IL-6, MMP-9, ADAMTS13, TNC, GSN and TRX, using Luminex assays or ELISA measurements. Compared with the levels assessed at the onset of AIS, the levels of MMP-9 (P < 0.001), ADAMTS13 (P < 0.001), and TRX (P < 0.001) significantly decreased after IVT. The level of IL-6 was significantly increased in the NIHSS > 5 group at admission (P < 0.001) compared to the NIHSS ≤ 5 group. AIS patients with a poor prognosis had lower levels of ADAMTS13 at 72 h post-IVT compared with patients with a good prognosis (P = 0.021). IL-6 also was notably higher in the poor outcome group (P = 0.012). After adjusting for confounders, ADAMTS13 at 72 h post-IVT was an independent protective factor for prognosis in AIS patients with an adjusted OR of 0.07 (P = 0.049), whereas IL-6 was an independent predictor of risk for AIS patients with an adjusted OR of 1.152 (P = 0.028). IVT decreased MMP-9, ADAMTS13, and TRX levels in the plasma of AIS patients. Patients with a NIHSS score of less than 5 exhibited lower IL-6 levels, indicating that increased levels of IL-6 correlated with AIS severity after IVT. Therefore, IL-6 and ADAMTS13 might be useful plasma markers to predict the prognosis in AIS patients at 90-days after IVT.

Composition and Organization of Acute Ischemic Stroke Thrombus: A Wealth of Information for Future Thrombolytic Strategies

During the last decade, significant progress has been made in understanding thrombus composition and organization in the setting of acute ischemic stroke (AIS). In particular, thrombus organization is now described as highly heterogeneous but with 2 preserved characteristics: the presence of (1) two distinct main types of areas in the core—red blood cell (RBC)-rich and platelet-rich areas in variable proportions in each thrombus—and (2) an external shell surrounding the core composed exclusively of platelet-rich areas. In contrast to RBC-rich areas, platelet-rich areas are highly complex and are mainly responsible for the thrombolysis resistance of these thrombi for the following reasons: the presence of platelet-derived fibrinolysis inhibitors in large amounts, modifications of the fibrin network structure resistant to the tissue plasminogen activator (tPA)-induced fibrinolysis, and the presence of non-fibrin extracellular components, such as von Willebrand factor (vWF) multimers and neutrophil extracellular traps. From these studies, new therapeutic avenues are in development to increase the fibrinolytic efficacy of intravenous (IV) tPA-based therapy or to target non-fibrin thrombus components, such as platelet aggregates, vWF multimers, or the extracellular DNA network.

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.

Effect of intravenous thrombolysis combined with mechanical thrombectomy on neurological function and short-term prognosis of patients with acute cerebral infarction

OBJECTIVE

This study was to assess the effect of intravenous thrombolysis combined with mechanical thrombectomy on neurological function and the short-term prognosis of patients with acute cerebral infarction (ACI).

METHODS

A total of 120 patients with ACI admitted to our hospital from January 2019 to January 2020 were selected as research objects, and randomized into Group A (n=60) or Group B (n=60). Patients in both groups were treated with intravenous thrombolysis. Group B received ACI conventional treatment and intravenous thrombolysis, while Group A was additionally given mechanical thrombectomy. Then the neurological function scores, serum factor levels, vascular recanalization rate, incidence of adverse reactions, Thrombolysis in Myocardial Infarction (TIMI) grade flow, and effective rate of treatment were compared between the two groups. The clinical trial is available at https://clinicaltrials.gov/, ClinicalTrials.gov Identifier: NCT03502411.

RESULTS

The neurological function scores of Group A were apparently lower than those of Group B one month after treatment (P<0.001). After treatment, Group A yielded a superior serum factor level compared to Group B (P<0.001), and also showed a higher recanalization rate of blood vessels and a notably lower adverse reaction rate (all P<0.05).

CONCLUSION

Intravenous thrombolysis combined with mechanical thrombectomy can accelerate the recovery of neurological function in patients with ACI, and yield a more promising outcome in terms of the patient's vascular recanalization rate compared with the monotherapy. It can also reduce the adverse reaction rate of patients to ensure a better short-term prognosis.

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.

Role of Neurons and Glia Cells in Wound Healing as a Novel Perspective Considering Platelet as a Conventional Player

Wound healing is a complex physiological process in which the damaged or injured tissue is replaced or regenerated by new cells or existing cells respectively in their synthesized and secreted matrices. Several cells modulate the process of wound healing including macrophages, fibroblasts, and keratinocytes. Apart from these cells, platelet has been considered as a major cellular fragment to be involved in wound healing at several stages by secreting its granular contents including growth factors, thus resulting in coagulation, inflammation, and angiogenesis. A distant cell, which is gaining significant attention nowadays due to its resemblance with platelet in several aspects, is the neuron. Not only neurons but also glia cells are also confirmed to regulate wound healing at different stages in an orchestrated manner. Furthermore, these neurons and glia cells mediate wound healing inducing tissue repair and regeneration apart from hemostasis, angiogenesis, and inflammation by secreting various growth factors, coagulation molecules, immunomodulatory molecules as well as neurohormones, neuropeptides, and neurotrophins. Therefore, in wound healing platelets, neurons and glia cells not only contribute to tissue repair but are also responsible for establishing the wound microenvironment, thus affecting the proliferation of immune cells, fibroblast, and keratinocytes. Here in this review, we will enlighten the physiological roles of neurons and glia cells in coordination with platelets to understand various cellular and molecular mechanism in brain injury and associated neurocognitive impairments.

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.

Diagnosis of Early Neurological Deterioration after Intravenous Thrombolysis for Patients with Cerebral Ischemic Stroke Using Compressed Sensing-Magnetic Resonance Imaging Algorithm

This study was to explore the risk factors and prognosis of early neurological deterioration (END) after intravenous thrombolysis in patients with cerebral ischemic stroke (CIS) with the guidance of magnetic resonance imaging (MRI) under the compressed sensing-MRI (CSMRI) algorithm. 187 patients with CIS in the hospital were selected and grouped into a deterioration group and a control group according to whether they had END. The CSMRI algorithm was constructed and compared with digital television (DTV) algorithm and Bayesian compressed sensing (BCS) algorithm. It was found that the reconstruction time of CSMRI algorithm in platform I (1134.9 s) and platform II (2615.8 s) was visibly lower than that of DTV algorithm (2634.6 s, 3963.4 s) and BCS algorithm (5631.5 s, 7412.3 s), showing statistically obvious differences (P < 0.05). In addition, the reconstruction efficiency of the CSMRI algorithm was the best. After 4 hours of intravenous thrombolysis, the stroke scale score (12.3 scores) of the deterioration group was much higher than that of the control group (8.4 scores) (P < 0.05). The occlusion of responsible great vessel in the deterioration group (30 cases, 83.33%) was obviously higher in contrast to that in the control group (74 cases, 49%) (P < 0.05). Stroke scale score and occlusion of responsible great vessel were risk factors for EBD after intravenous thrombolysis.

Association between clot composition and stroke origin in mechanical thrombectomy patients: analysis of the Stroke Thromboembolism Registry of Imaging and Pathology

BACKGROUND

We retrospectively evaluated the composition of retrieved clots from ischemic stroke patients to study the association between histological composition and stroke etiology METHODS: Consecutive patients enrolled in the Stroke Thromboembolism Registry of Imaging and Pathology (STRIP) were included in this study. All patients underwent mechanical thrombectomy and retrieved clots were sent to a central core lab for processing. Histological analysis was performed using martius scarlet blue (MSB) staining, and quantification for red blood cells (RBCs), white blood cells (WBCs), fibrin and platelets was performed using Orbit Image Software. A Wilcoxon test was used for continuous variables and χ² test for categorical variables.

RESULTS

1350 patients were included in this study. The overall rate of Thrombolysis In Cerebral Infarction (TICI) 2c/3 was 68%. 501 patients received tissue plasminogen activator (tPA) (37%). 267 patients (20%) had a large artery atherosclerosis (LAA) source, 662 (49%) a cardioembolic (CE) source, 301 (22%) were cryptogenic, and the remainder had other identifiable sources including hypercoagulable state or dissection. LAA thrombi had a higher mean RBC density (46±23% vs 42±22%, p=0.01) and a lower platelet density (24±18% vs 27±18%, p=0.03) than CE thrombi. Clots from dissection patients had the highest mean RBC density (50±24%) while clots from patients with a hypercoagulable state had the lowest mean RBC density (26±21%).

CONCLUSIONS

Our study found statistically significant but clinically insignificant differences between clots of CE and LAA etiologies. Future studies should emphasize molecular, proteomic and immunohistochemical characteristics to determine links between clot composition and etiology.

Inside the Thrombus: Association of Hemostatic Parameters With Outcomes in Large Vessel Stroke Patients

Background: Actual clinical management of ischemic stroke (IS) is based on restoring cerebral blood flow using tissue plasminogen activator (tPA) and/or endovascular treatment (EVT). Mechanical thrombectomy has permitted the analysis of thrombus structural and cellular classic components. Nevertheless, histological assessment of hemostatic parameters such as thrombin-activatable fibrinolysis inhibitor (TAFI) and matrix metalloproteinase 10 (MMP-10) remains unknown, although their presence could determine thrombus stability and its response to thrombolytic treatment, improving patient's outcome.

Methods: We collected thrombi (n = 45) from large vessel occlusion (LVO) stroke patients (n = 53) and performed a histological analysis of different hemostatic parameters [TAFI, MMP-10, von Willebrand factor (VWF), and fibrin] and cellular components (erythrocytes, leukocytes, macrophages, lymphocytes, and platelets). Additionally, we evaluated the association of these parameters with plasma levels of MMP-10, TAFI and VWF activity and recorded clinical variables.

Results: In this study, we report for the first time the presence of MMP-10 and TAFI in all thrombi collected from LVO patients. Both proteins were localized in regions of inflammatory cells, surrounded by erythrocyte and platelet-rich areas, and their content was significantly associated (r = 0.41, p < 0.01). Thrombus TAFI was lower in patients who died during the first 3 months after stroke onset [odds ratio (OR) (95%CI); 0.59 (0.36–0.98), p = 0.043]. Likewise, we observed that thrombus MMP-10 was inversely correlated with the amount of VWF (r = −0.30, p < 0.05). Besides, VWF was associated with the presence of leukocytes (r = 0.37, p < 0.05), platelets (r = 0.32, p < 0.05), and 3 months mortality [OR (95%CI); 4.5 (1.2–17.1), p = 0.029]. Finally, plasma levels of TAFI correlated with circulating and thrombus platelets, while plasma MMP-10 was associated with cardiovascular risk factors and functional dependence at 3 months.

Conclusions: The present study suggests that the composition and distribution of thrombus hemostatic components might have clinical impact by influencing the response to pharmacological and mechanical therapies as well as guiding the development of new therapeutic strategies.

Thrombus Composition and Efficacy of Thrombolysis and Thrombectomy in Acute Ischemic Stroke

Thrombi retrieved from patients with acute ischemic stroke are highly heterogeneous. Recent data suggest that thrombus composition may impact on mechanical thrombectomy, the number of recanalization manoeuvres, resistance to retrieval, and on thrombolytic potential. Our aim was to summarize evidence describing the impact of thrombus composition on efficacy of mechanical thrombectomy and thrombolysis in patients with acute ischemic stroke. The scoping review methodology guided by the Joanna Briggs Institute, an adaption of the Arksey and O'Malley, was followed. Comprehensive searches were conducted in MEDLINE, EMBASE, SCOPUS, and Web of Science. Articles were classified into 4 key themes: (1) composition of stroke thrombi, (2) thrombus composition and mechanical thrombectomy, (3) thrombus composition and thrombolytic therapy, and (4) novel imaging and endovascular approaches. Our search identified 698 articles published from 1987 to June 2020. Additional articles were extracted from reference lists of the selected articles. Overall, 95 topic-specific articles identified for inclusion published in 40 different journals were included. Reports showed that thrombus composition in stroke was highly heterogeneous, containing fibrin, platelets, red blood cells, VWF (von Willebrand Factor), and neutrophil extracellular traps. Thrombi could roughly be divided into fibrin- and red blood cell-rich clots. Fibrin-rich clots were associated with increased recanalization manoeuvres, longer procedure time, and less favorable clinical outcomes compared with red blood cell-rich clots. Advances in detection or treatment of thrombi that take into account clot heterogeneity may be able to improve future endovascular and thrombolytic treatment of stroke.

Biomarkers of Unfavorable Outcome in Acute Ischemic Stroke Patients with Successful Recanalization by Endovascular Thrombectomy

<b><i>Background:</i></b> We aimed to identify plasma markers of unfavorable outcomes for patients with acute ischemic stroke (AIS) after recanalization by endovascular thrombectomy (EVT). <b><i>Methods:</i></b> From November 2017 to May 2019, we prospectively collected 61 AIS patients due to anterior large vessel occlusion who achieved recanalization by EVT. Plasma samples were obtained between 18 and 24 h after recanalization. Unfavorable outcomes included futile recanalization at 90 days and overall early complications within 7 days after EVT. <b><i>Results:</i></b> After adjustment for age and initial National Institute of Health Stroke Scale (NIHSS), matrix metalloproteinase-9 (MMP-9), tenascin-C, thioredoxin, ADAMTS13, and gelsolin were independently associated with both futile recanalization and overall early complications significantly (all <i>p</i> &#x3c; 0.05), while C-reactive protein (CRP) was independently associated with overall early complications (<i>p</i> = 0.031) but at the limit of significance for futile recanalization (<i>p</i> = 0.051). The baseline clinical model (BCM) (including age and initial NIHSS) demonstrated discriminating ability to indicate futile recanalization (area under the curve [AUC] 0.807, 95% confidence interval [CI] 0.693–0.921) and overall early complications (AUC 0.749, 95% CI 0.611–0.887). BCM+MMP-9+thioredoxin enhanced discrimination (AUC 0.908, 95% CI 0.839–0.978, <i>p</i> = 0.043) and reclassification (net reclassification improvement [NRI] 67.2%, <i>p</i> &#x3c; 0.001) to indicate futile recanalization. With respect to overall early complications, BCM+MMP-9+tenascin-C, BCM+MMP-9+CRP, BCM+MMP-9+ADAMTS13, BCM+tenascin-C+ADAMTS13, and BCM+CRP+ADAMTS13, all improved discrimination (AUC [95% CI]: 0.868 [0.766–0.970], 0.882 [0.773–0.990], 0.886 [0.788–0.984], 0.880 [0.783–0.977], and 0.863 [0.764–0.962], respectively, all <i>p</i> &#x3c; 0.05 by the DeLong method) and reclassification (NRI 59.1%, 71.8%, 51.1%, 67.4%, and 38.3%, respectively, all <i>p</i> &#x3c; 0.05). <b><i>Conclusions:</i></b> The increased levels of MMP-9, tenascin-C, CRP, thioredoxin, and decreased levels of ADAMTS13 and gelsolin were independent predictors of futile recanalization in AIS patients after recanalization by EVT.

Quantitative Morphology of Cerebral Thrombi Related to Intravital Contraction and Clinical Features of Ischemic Stroke

BACKGROUND AND PURPOSE

The purpose was to assess quantitatively and qualitatively the composition and structure of cerebral thrombi and correlate them with the signs of intravital clot contraction (retraction), as well as with etiology, severity, duration, and outcomes of acute ischemic stroke.

METHODS

We quantified high-resolution scanning electron micrographs of 41 cerebral thrombi for their detailed cellular and noncellular composition and analyzed histological images for the overall structure with the emphasis on red blood cell compression, fibrin age, and the signs of inflammation.

RESULTS

Cerebral thrombi were quite compact and had extremely low porosity. The prevailing cell type was polyhedral compressed erythrocytes (polyhedrocytes) in the core, and fibrin-platelet aggregates were concentrated at the periphery; both findings are indicative of intravital contraction of the thrombi. The content of polyhedrocytes directly correlated with the stroke severity. The prevalence of fibrin bundles was typical for more severe cases, while the content of fibrin sponge prevailed in cases with a more favorable course. The overall platelet content in cerebral thrombi was surprisingly small, while the higher content of platelet aggregates was a marker of stroke severity. Fibrillar types of fibrin prevailed in atherothrombogenic thrombi. Older fibrin prevailed in thrombi from the patients who received thrombolytics, and younger fibrin dominated in cardioembolic thrombi. Alternating layers of erythrocytes and fibrin mixed with platelets were common for thrombi from the patients with more favorable outcomes. Thrombi with a higher number of leukocytes were associated with fatal cases.

CONCLUSIONS

Most cerebral thrombi undergo intravital clot contraction (retraction) that may be of underestimated clinical importance. Despite the high variability of the composition and structure of cerebral thrombi, the content of certain types of blood cells and fibrin structures combined with the morphological signs of intravital contraction correlate with the clinical course and outcomes of acute ischemic stroke.

Traumatic injury results in prolonged circulation of ultralarge von Willebrand factor and a reduction in ADAMTS13 activity

BACKGROUND

Increases in plasma von Willebrand Factor (VWF) levels, accompanied by decreases in the metalloprotease ADAMTS13, have been demonstrated soon after traumatic injury while downstream effects remain unclear.

STUDY DESIGN AND METHODS

A cohort of 37 injured trauma patients from a randomized control trial investigating the use of prehospital plasma transfusion were analyzed for activity and antigen levels of ADAMTS13 and VWF at 0 and 24 hours after admission. Relevant clinical data were abstracted from the medical records. Trauma patient plasma was analyzed via agarose gel electrophoresis to evaluate the effects of injury on VWF multimer composition compared to healthy controls.

RESULTS

von Willebrand factor levels were elevated at presentation (189% [110%-263%] vs. 95% [74%-120%]), persisting through 24 hours (213% [146%-257%] vs. 132% [57%-160%]), compared to healthy controls. Ultralarge VWF (UL-VWF) forms were elevated in trauma patients at both 0 and 24 hours, when compared to pooled normal plasma (10.0% [8.9%-14.3%] and 11.3% [9.1%-21.2%], respectively, vs. 0.6%). Circulating plasma ADAMTS13 activity was decreased at 0 hours (66% [47%-86%] vs. 100% [98%-100%]) and at 24 hours (72.5% [56%-87.3%] vs. 103% [103%-103%]) in trauma patients. ADAMTS13 activity independently predicted the development of coagulopathy and correlated with international normalized ratio, thromboelastography values, injury severity, and blood product transfusion.

CONCLUSION

Traumatic injury is associated with acute coagulopathy that is characterized by increased UL-VWF multimers and reduction in ADAMTS13, which correlates with blood loss, transfusion requirement, and injury severity. These findings suggest the potential for future trials targeting ADAMTS13 repletion to enhance clearance of VWF multimers.

von Willebrand Factor and Platelet Glycoprotein Ib: A Thromboinflammatory Axis in Stroke

von Willebrand factor (VWF) and platelets are key mediators of normal hemostasis. At sites of vascular injury, VWF recruits platelets via binding to the platelet receptor glycoprotein Ibα (GPIbα). Over the past decades, it has become clear that many hemostatic factors, including VWF and platelets, are also involved in inflammatory processes, forming intriguing links between hemostasis, thrombosis, and inflammation. The so-called “thrombo-inflammatory” nature of the VWF-platelet axis becomes increasingly recognized in different cardiovascular pathologies, making it a potential therapeutic target to interfere with both thrombosis and inflammation. In this review, we discuss the current evidence for the thrombo-inflammatory activity of VWF with a focus on the VWF-GPIbα axis and discuss its implications in the setting of ischemic stroke.

[Prognostic value of endothelial dysfunction and von Willebrand factor in acute and chronic hemispheric intracerebral hemorrhage]

AIM

To study the changes in endothelial dysfunction and von Willebrand factor activity in acute and chronic stages of hemispheric intracerebral hemorrhage (ICH) and their influence on clinical severity and functional recovery.

MATERIAL AND METHODS

Fifty patients with hemispheric ICH, aged 61.6±11.2 years, and 30 patients with AH, aged 59.6±6.2 years, (comparison group) were examined. Patients with ICH were examined on admission, 6-8^th, 13-15^th days, and 11.1±0.9 months after stroke onset. Patients with arterial hypertension (AH) were examined on admission. Changes in NIHSS, Glasgow coma scale, and modified Rankin scale were studied. Restocetin induced platelet aggregation (RIPA) was assessed by optical aggregometry (BIOLA LA230-2 AGGRWB) in modification by G. Born and Z. Gabbasov. von Willebrand factor (vWF) activity was examined as described by J. Olson.

RESULTS

RIPA was significantly higher in acute ICH compared to chronic ICH, AH and reference values. RIPA values were negatively correlated with hematoma volume and midline shift (r≥ -0.308, p≤0.035). vWF activity was significantly higher in ICH patients than in AH and reference values. Patients with AH also had significantly higher vWF activity than reference values. In acute ICH, vWF activity steadily increased reaching maximal values by 13-15^th day. In chronic ICH, vWF activity decreased compared to the acute phase, but still remained higher than in AH patients or reference values. In acute phase, 1% increment in vWF values resulted in 0.5% increase in the risk of death during the follow-up period (95% CI 1.001-1.008, p=0.007).

CONCLUSION

Endothelial dysfunction assessed by vWF activity increases during the acute hemispheric ICH and remains elevated in the chronic stage. vWF activity may be used as a marker in assessing stroke outcome and prognosis.

Insights from thrombi retrieved in stroke due to large vessel occlusion

The recent advances of endovascular procedures to treat stroke due to large cerebral vessel occlusion have made it possible to analyze the retrieved thrombus material. Analysis of cerebral thrombi is emerging as a relevant opportunity to complement the diagnostic workup of etiology, to develop new lytic approaches and to optimize the acute treatment of stroke due to large vessel occlusion. Nonetheless, retrieved thrombi are frequently discarded since their informative potential is often neglected and standards are missing. This review provides an overview of the current knowledge and expanding research relating to thrombus composition analysis in large vessel occlusions. We first discuss the heterogeneity of thrombogenic factors that underlie the thrombotic formation in stroke and its implications to identify stroke etiology and thrombus age. Further, we show that understanding structural characteristics of thrombus is pivotal for the development of new-targeted lytic therapies as well as to improve, through thrombus modeling, the development of thrombectomy devices. Finally, we discuss the on-going attempts to identify a signature of thrombus composition indirectly through imaging and peripheral blood biomarkers, which might in future assist treatment decision-making as well as secondary prevention. Thrombus analysis might contribute to the advancement and optimization of personalized stroke treatments.

Matrix metalloproteinases and ADAMs in stroke

Stroke is a leading cause of death and disability worldwide. However, after years of in-depth research, the pathophysiology of stroke is still not fully understood. Increasing evidence shows that matrix metalloproteinases (MMPs) and "a disintegrin and metalloproteinase" (ADAMs) participate in the neuro-inflammatory cascade that is triggered during stroke but also in recovery phases of the disease. This review covers the involvement of these proteins in brain injury following cerebral ischemia which has been widely studied in recent years, with efforts to modulate this group of proteins in neuroprotective therapies, together with their implication in neurorepair mechanisms. Moreover, the review also discusses the role of these proteins in specific forms of neurovascular disease, such as small vessel diseases and intracerebral hemorrhage. Finally, the potential use of MMPs and ADAMs as guiding biomarkers of brain injury and repair for decision-making in cases of stroke is also discussed.

ADAMTS13: An Emerging Target in Stroke Therapy

Thrombosis is the predominant underlying mechanism of acute ischemic stroke (AIS). Though thrombolysis with tPA has been proven to be effective in treating AIS within the time window, the majority of AIS patients fail to receive tPA due to various reasons. Current medical therapies for AIS have limited efficacy and pose a risk of intracerebral hemorrhage. ADAMTS13 (a disintegrin and metalloprotease with a thrombospondin type 1 motif, member 13) is a metalloprotease that effectively breaks down the von Willebrand Factor (VWF), a key factor in thrombus formation. Previous studies have proven that dysfunction of ADAMTS13 is associated with many diseases. Recently, ADAMTS13 has been reported to be closely related to stroke. In this review, we briefly described the structure of ADAMTS13 and its role in thrombosis, inflammation, as well as angiogenesis. We then focused on the relationship between ADAMTS13 and AIS, ranging from ischemic stroke occurrence, to AIS treatment and prognosis. Based on research findings from in vitro, animal, and clinical studies, we propose that ADAMTS13 is a potential biomarker to guide appropriate treatment for ischemic stroke and a promising therapeutic agent for tPA resistant thrombi.

Acid-Base and Electrolyte Changes Drive Early Pathology in Ischemic Stroke

Emergent large vessel occlusion accounts for 20-40% of ischemic strokes and is the most debilitating form of stroke. Some of the earliest changes in response to ischemic stroke occur in blood gases and electrolytes. These biochemical changes occur within minutes after occlusion in experimental models of stroke and can be utilized to predict stroke outcomes. The majority of ELVO stroke patients are middle-aged to elderly and are of both sexes, revealing that there is an age and sex mismatch between ischemic stroke patients and animal models, since most experimental studies use young male rats. Rethinking of the animal models should be considered, especially in encouraging the use of aged male and female rats with comorbidities to more closely mirror human populations. Mechanical thrombectomy provides a unique opportunity for researchers to further this work by expanding the collection and analysis of blood samples that are adjacent to the thrombus. To understand the complexity of stroke, researchers can analyze these tissues for different molecular targets that occur in response to ischemic stroke. This information may aid in the reduction of symptom burden for individuals diagnosed with ischemic stroke. Investigators should also focus on data from ischemic stroke patients and attempt to discover target molecules and then in animal models to establish mechanism, which will aid in the development of new stroke therapies. This review discusses the translation of these studies to the human patient to develop the capability to predict stroke outcomes. Future studies are needed to identify molecular targets to predict the risk of worsened long-term outcomes and/or increased risk for mortality.

Markers of Coagulation and Fibrinolysis Predicting the Outcome of Acute Ischemic Stroke Thrombolysis Treatment: A Review of the Literature

Intravenous administration of recombinant tissue plasminogen activator (rt-PA) has been proven to be safe and effective in the treatment of acute ischemic stroke. Little is known, however, why this treatment is less effective in some patients while in others life-threatening side-effects, e.g., symptomatic intracerebral hemorrhage might occur. Clinical failure of thrombolysis related to absent or partial recanalization or reocclusion as well as hemorrhagic complications of thrombolysis are possibly related to hemostatic events. Data on markers of coagulation and/or fibrinolysis in acute stroke patients are numerous and may provide indications regarding therapy outcomes. Better understanding of the hemostatic and fibrinolytic system during rt-PA therapy might be clinically useful and ultimately might lead to an improvement in the efficacy or safety of this treatment. Studies on thrombus composition retrieved from cerebral arteries may also advance our knowledge and provide a key to improve acute stroke therapy. Here we provide a comprehensive review on a wide range of factors and markers of coagulation and fibrinolysis that have been studied in the context of thrombolysis outcome in ischemic stroke patients. Moreover, a brief summary is given on the most recent research on thrombus composition having a potential influence on outcomes.

Correlation of imaging and histopathology of thrombi in acute ischemic stroke with etiology and outcome

Mechanical thrombectomy has become the stand of care for patients with large vessel occlusions, yet major improvements in thrombectomy speed, efficacy, and completeness can still be achieved. High rates of clot fragmentation and failure to remove the clot resulting in poor neurological outcomes suggest that in order to further advance the field of stroke intervention we must turn our attention towards understanding the science of clot. Accurately identifying the composition of the occlusive clot prior to intervention could significantly influence the success of the revascularization strategy used to treat them. Numerous features of thromboemboli could be studied and characterized, including quantitative histomorphometry and diagnostic imaging characteristics. Each of these features might logically predict superior thrombectomy outcomes with one device or another. This article aims to review the current literature on histopathological composition of acute ischemic stroke clots, with a particular focus on the correlation between clot composition and diagnostic imaging, stroke etiology and revascularization outcomes.

Thrombocytopenia and declines in platelet counts: predictors of mortality and outcome after mechanical thrombectomy

BACKGROUND AND PURPOSE

Acute ischemic stroke (AIS) has well-known risk factors. The role of platelets in patients treated using mechanical thrombectomy (MT) has not been studied. The aim of this study was to study if there is an association of initial thrombocytopenia (TP) and a decline of platelets counts (DPC) with the clinical outcomes, mortality and intracranial hemorrhage (ICH) rates in AIS patients treated with MT.

MATERIALS AND METHODS

In a case-control study consecutive MT-stroke patients were analyzed. A multivariate logistic regression model was used to test for good clinical outcome (mRS 90 days <= 2) and mortality adjusting for age, initial NIHSS, pretreatment with tPA, statins and platelet inhibitors, occlusion site, time from symptom onset to recanalization, initial TP (< 150 × 10⁹/L) and DPC (> 26%). Additionally, rates of ICH were compared.

RESULTS

Of 294 patients included, 9.6% had an initial TP and 23.8% a DPC > 26%. The mortality rate in patients with normal platelet counts was 26.1% vs. 48.3% (p = 0.002) in patients with initial TP with an aOR of 3.47 (CI 1.28-9.4, p = 0.005). No difference regarding the rate of good clinical outcome (p = 0.204) and ICH (p = 0.18) was observed. A DPC of more than 26% during the first 5 days of hospitalization predicted the rate of mortality (aOR 2.4 CI 1.14-5.04, p = 0.021) and the chances of a good clinical outcome (aOR 0.291 CI 0.128-0.666, p = 0.003) without significant differences of ICH rates (p = 0.735).

CONCLUSION

In AIS patients treated with MT an initial TP was independently associated with higher mortality rates and a marked DPC with higher mortality rates as well as poorer clinical outcomes.

Comparison of Mechanical Thrombectomy with Contact Aspiration, Stent Retriever, and Combined Procedures in Patients with Large-Vessel Occlusion in Acute Ischemic Stroke

Background

We investigated the properties and effects of 5 mechanical thrombectomy procedures in patients with acute ischemic stroke. The relationships between the type of procedure, the time required, the success of recanalization, and the clinical outcome were analyzed.

Material/Methods

This prospective comparative analysis included 500 patients with acute ischemic stroke and large-vessel occlusion. We compared contact aspiration thrombectomy (ADAPT, n=100), stent retriever first line (SRFL, n=196), the Solumbra technique (n=64), mechanical thrombectomy plus stent implantation (n=81), and a combined procedure (n=59).

Results

ADAPT provided shorter procedure (P<0.001) and recanalization times (P<0.001) than the other techniques. Better clinical outcome was achieved for ischemia in the anterior circulation than ischemia in the posterior fossa (P<0.001). Compared to the other techniques, patients treated with ADAPT procedure had increased odds of achieving better mTICI scores (P=0.002) and clinical outcome (NIHSS) after 7 days (P=0.003); patients treated with SRFL had increased odds of achieving better long-term clinical status (3M-mRS=0–2; P=0.040). Patients with SRFL and intravenous thrombolysis (IVT) had increased odds of better clinical status (3M-mRS=0–2; P=0.031) and decreased odds of death (P=0.005) compared to patients with SRFL without IVT. The other treatment approaches had no additional effect of IVT. Patients with SRFL with a mothership transfer had increased odds of achieving favorable clinical outcome (3M-mRS) compared to SRFL with the drip-and-ship transfer paradigm (P=0.015).

Conclusions

Our results showed that ADAPT and SRFL provided significantly better outcomes compared to the other examined techniques. A mothership transfer and IVT administration contributed to the success of the SRFL approach.

Correlation of imaging and histopathology of thrombi in acute ischemic stroke with etiology and outcome: a systematic review

BACKGROUND AND PURPOSE

Studying the imaging and histopathologic characteristics of thrombi in ischemic stroke could provide insights into stroke etiology and ideal treatment strategies. We conducted a systematic review of imaging and histologic characteristics of thrombi in acute ischemic stroke.

MATERIALS AND METHODS

We identified all studies published between January 2005 and December 2015 that reported findings related to histologic and/or imaging characteristics of thrombi in acute ischemic stroke secondary to large vessel occlusion. The five outcomes examined in this study were (1) association between histologic composition of thrombi and stroke etiology; (2) association between histologic composition of thrombi and angiographic outcomes; (3) association between thrombi imaging and histologic characteristics; (4) association between thrombi imaging characteristics and angiographic outcomes; and (5) association between imaging characteristics of thrombi and stroke etiology. A meta-analysis was performed using a random effects model.

RESULTS

There was no significant difference in the proportion of red blood cell (RBC)-rich thrombi between cardioembolic and large artery atherosclerosis etiologies (OR 1.62, 95% CI 0.1 to 28.0, p=0.63). Patients with a hyperdense artery sign had a higher odds of having RBC-rich thrombi than those without a hyperdense artery sign (OR 9.0, 95% CI 2.6 to 31.2, p<0.01). Patients with a good angiographic outcome had a mean thrombus Hounsfield unit (HU) of 55.1±3.1 compared with a mean HU of 48.4±1.9 for patients with a poor angiographic outcome (mean standard difference 6.5, 95% CI 2.7 to 10.2, p<0.001). There was no association between imaging characteristics and stroke etiology (OR 1.13, 95% CI 0.32 to 4.00, p=0.85).

CONCLUSIONS

The hyperdense artery sign is associated with RBC-rich thrombi and improved recanalization rates. However, there was no association between the histopathological characteristics of thrombi and stroke etiology and angiographic outcomes.