Per pass analysis of thrombus composition retrieved by mechanical thrombectomy

BACKGROUND AND AIM

Mechanical thrombectomy (MT) for large vessel occlusion often requires multiple passes to retrieve the entire thrombus load. In this multi-institutional study we sought to examine the composition of thrombus fragments retrieved with each pass during MT.

METHODS

Patients who required multiple passes during thrombectomy were included. Histopathological evaluation of thrombus fragments retrieved from each pass was performed using Martius Scarlet Blue staining and the composition of each thrombus component including RBC, fibrin and platelet was determined using image analysis software.

RESULTS

154 patients underwent MT and 868 passes was performed which resulted in 263 thrombus fragments retrieval. The analysis of thrombus components per pass showed higher RBC, lower fibrin and platelet composition in the pass 1 and 2 when compared to pass 3 and passes 4 or more combined (P values <0.05). There were no significant differences between thrombus fragments retrieved in pass 1 and pass 2 in terms of RBC, WBC, fibrin, and platelet composition (P values >0.05). Similarly, when each composition of thrombus fragments retrieved in pass 3 and passes 4 or more combined were compared with each other, no significant difference was noted (P values >0.05).

CONCLUSION

Our findings confirm that thrombus fragments retrieved with each pass differed significantly in histological content. Fragments in the first passes were associated with lower fibrin and platelet composition compared to fragments retrieved in passes three and four or higher. Also, thrombus fragments retrieved after failed pass were associated with higher fibrin and platelet components.

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.

Novel Focal Therapeutic Hypothermia Device for Treatment of Acute Neurologic Injury: Large Animal Safety and Efficacy Trial

Objective Therapeutic hypothermia is a potentially powerful and controversial clinical tool for neuroprotection following acute neurologic pathology, particularly vascular injury. Indeed, therapeutic hypothermia remains a standard of care for postcardiac arrest ischemia and acute neonatal hypoxic-ischemic encephalopathy, improving both survival and outcomes. Although therapeutic hypothermia remains promising for cellular and systems-based neuronal protection in other neurologic injury states, the systemic side effects have limited clinical utility, confounded analysis of potential neurologic benefits, and precluded the completion of meaningful clinical trials.

Methods To address such limitations, we developed and tested a novel, minimally invasive, neurocritical care device that employs continuous circulation of cold saline through the pharyngeal region to deliver focal cerebrovascular cooling. We conducted a preclinical safety and efficacy trial in six adult porcine animals to assess the validity and functionality of the NeuroSave device, and assess cooling potential following middle cerebral artery occlusion (n = 2).

Results NeuroSave consistently lowered brain parenchymal temperature by a median of 9°C relative to core temperature within 60 minutes of initiation, including in ischemic cerebral parenchyma. The core body temperature experienced a maximal reduction of 2°C, or 5% of body temperature, with no associated adverse effects identified.

Conclusion The present study uses a large animal preclinical model to demonstrate the safety and efficacy of a novel, noninvasive device for the induction of robust and systemically safe hypothermia within the brain.

Assessment of Blood Clot Composition by Spectral Optical Coherence Tomography: An In Vitro Study

PURPOSE

Optical coherence tomography (OCT) has the potential for in vivo clot composition characterization in difficult mechanical embolectomy cases. We performed an in vitro study to determine the OCT characteristics of red blood cells (RBCs) and fibrin rich clots.

MATERIALS AND METHODS

Analogues of 5 compositions of clots (5% to 95% RBCs from Group A to E) were created from human blood. The blood mixture was injected into the bifurcation of a 3D printed bifurcated silicone tube. The OPTISTM Integrated System (St. Jude Medical Inc.) was used to identify the magnitude of OCT signals from different compositions of clots. Martius Scarlett Blue trichrome (MSB) staining was performed to confirm the composition of RBCs and fibrin in each clot.

RESULTS

Group A and B showed less signal attenuation (less than 30%) from its surface to the inside, which indicated high penetration (low-back scattering). Group C indicated intermediate signal attenuation (60%) from its surface to inside the clots, in which signals were found even at the periphery of the clot. Group D and E were superficially signal rich with more signal attenuation (more than 80%) from its surface to the inside indicating low penetration (high-back scattering). Signal-free shadowing was shown in 3 clots in Group E. MSB staining indicated color change (from red in fibrin-rich clots to yellow in RBC-rich clots).

CONCLUSION

Different compositions of clots can be assessed using OCT. Fibrin-rich clots have homogeneous signals with high penetration, while RBC-rich clots can be recognized as superficially signal rich with low penetration.

A novel rabbit thromboembolic occlusion model

BACKGROUND

To develop a preclinical thromboembolic occlusion model for studying revascularization strategies.

METHODS

Clot analog with barium sulfate was injected into the distal aorta in 9 New Zealand white rabbits. The situation of aorta occlusion was compared among fibrin-rich (n=4), red blood cell (RBC)-rich (n=3), and whole blood clot analogs (n=2) using digital subtraction angiography. Arterial geometries, histologic features and circumferential stretch of the distal aorta in rabbits were compared with the common carotid artery in swine and the distal internal carotid artery (ICA) in humans. Aspiration thrombectomy and mechanical thrombectomy using a stent retriever were performed in two rabbits.

RESULTS

The aortic bifurcation was occluded after a single delivery of clot in 4 cases. It was occluded after the second clot injection in the 5 remaining rabbits. Fragmentation of RBC-rich clots occurred during clot injection in 2 cases. The mean diameters of the distal aorta and right common iliac artery in rabbits were 3.7±0.4 and 2.8±0.3 mm, respectively; the mean diameters of human ICA, and first and second segments of the middle cerebral artery (M1, M2) were 3.6±0.4, 3.1±0.4, and 2.4±0.4 mm, respectively. Arterial revascularization was achieved in both rabbits. Geometric, mechanical and histological factors of the distal aorta in rabbit were more close to human distal ICA than swine carotid artery.

CONCLUSION

Arterial occlusion can be achieved at the aortic bifurcation in rabbits, which is comparable to human ICA bifurcation. This thrombectomy model has the potential to be used for testing of thrombectomy devices.

Clot composition in retrieved thrombi after mechanical thrombectomy in strokes due to carotid web

BACKGROUND

The association of carotid webs (CaW) and ischemic stroke is being increasingly recognized. Data on the histologic clot architecture in strokes caused by CaW has not been previously described. Understanding thrombi histopathology may provide insight into the pathophysiology of CaW-related strokes.

METHODS

This case series presents three patients with acute ischemic stroke thought to be caused by ipsilateral CaW. Thromboemboli were retrieved from the middle cerebral artery (MCA) by mechanical thrombectomy and histologic analysis was performed.

RESULTS

Three patients aged between 41 and 55 years with few to no vascular risk factors presented with symptoms concerning for an acute MCA territory infarction (National Institutes of Health Stroke Scale (NIHSS) range 10-17). Non-contrast computed tomography (CT) Alberta Stroke Program Early CT Score (ASPECTS) range was 7-8 and all patients had hyperdense vessel sign. Initial CT angiogram was concerning for CaW with no superimposed thrombus, later confirmed with conventional angiography. All patients underwent thrombectomy with full reperfusion. Comprehensive stroke workup failed to reveal other etiologies besides ipsilateral CaW. The histopathologic appearance was of typical fresh mixed thrombi. Qualitative thrombus composition analysis of clot from Case #1 yielded 42.5% fibrin, 50.0% red blood cells (RBC), and 7.5% white blood cells (WBC); Case #2 yielded 46.9% fibrin, 43.4% RBC, and 9.7% WBC; and Case #3 yielded 61.5% fibrin, 31.8% RBC, and 6.7% WBC.

CONCLUSIONS

The clot composition of large vessel occlusion strokes from CaW is comparable to the histopathology of previously reported clots from other stroke etiologies. Advanced staining techniques may aid in further characterizing the thrombi of this poorly understood condition.

WEB Device Shape Changes in Elastase-Induced Aneurysms in Rabbits

BACKGROUND AND PURPOSE

While WEB devices have been shown to be safe and effective for aneurysm treatment, WEB-shape modification compression has been associated with incomplete aneurysm occlusion. We explored the relationship between occlusion rates and WEB-shape modification in different WEB device types in an experimental aneurysm model.

MATERIALS AND METHODS

Elastase-induced aneurysms were created in rabbits and treated with dual-layer (n = 12), single-layer (n = 12), or single-layer sphere (n = 12) WEB devices. Aneurysms were followed up either at 3 or 12 months. Angiographic occlusion was graded using the WEB Occlusion Scale: grade I, complete; grade II, complete but recess filling; grade III, residual neck; or grade IV, residual aneurysm. WEB-shape modification and histologic features were also analyzed.

RESULTS

Grade I or II occlusion was seen in 16 (44%) aneurysms, and grade I, II, or III ("adequate") occlusion was observed in 22 (61.1%) aneurysms at follow-up. WEB-shape modification was observed in 22 (61.1%) aneurysms. WEB-shape modification was higher in single-layer (9/12) and dual-layer (10/12) devices compared with single-layer sphere devices (3/12). Aneurysms with WEB-shape modification had a higher level of thrombus organization in the dome compared with those without WEB-shape modification (68% [15/22] versus 50% [7/14]). WEB-shape modification was not correlated with angiographic or histologic outcomes but was significantly correlated with levels of fibrosis and smooth muscle cells in the aneurysm.

CONCLUSIONS

WEB-shape modification is not associated with incomplete aneurysm occlusion of WEB devices in the rabbit model but may be related to connective tissue formation and the healing response to WEB device implantation.

Adaptive Remodeling in the Elastase-induced Rabbit Aneurysms

BACKGROUND

Rupture of brain aneurysms is associated with high fatality and morbidity rates. Through remodeling of the collagen matrix, many aneurysms can remain unruptured for decades, despite an enlarging and evolving geometry.

OBJECTIVE

Our objective was to explore this adaptive remodeling for the first time in an elastase induced aneurysm model in rabbits.

METHODS

Saccular aneurysms were created in 22 New Zealand white rabbits and remodeling was assessed in tissue harvested 2, 4, 8 and 12 weeks after creation.

RESULTS

The intramural principal stress ratio doubled after aneurysm creation due to increased longitudinal loads, triggering a remodeling response. A distinct wall layer with multi-directional collagen fibers developed between the media and adventitia as early as 2 weeks, and in all cases by 4 weeks with an average thickness of 50.6 ± 14.3 μm. Collagen fibers in this layer were multi-directional (AI = 0.56 ± 0.15) with low tortuosity (1.08 ± 0.02) compared with adjacent circumferentially aligned medial fibers (AI = 0.78 ± 0.12) and highly tortuous adventitial fibers (1.22 ± 0.03). A second phase of remodeling replaced circumferentially aligned fibers in the inner media with longitudinal fibers. A structurally motivated constitutive model with both remodeling modes was introduced along with methodology for determining material parameters from mechanical testing and multiphoton imaging.

CONCLUSIONS

A new mechanism was identified by which aneurysm walls can rapidly adapt to changes in load, ensuring the structural integrity of the aneurysm until a slower process of medial reorganization occurs. The rabbit model can be used to evaluate therapies to increase aneurysm wall stability.

High-resolution scanning electron microscopy for the analysis of three-dimensional ultrastructure of clots in acute ischemic stroke

BACKGROUND

Characterization of acute ischemic stroke (AIS) clots has typically focused on two-dimensional histological analysis of the thrombus. The three-dimensional (3D) architecture and distribution of components within emboli have not been fully investigated. The aim of this study was to examine the composition and microstructure of AIS clots using histology and serial block-face scanning electron microscopy (SBFSEM).

METHODS

As part of the multi-institutional STRIP registry, 10 consecutive AIS emboli were collected from 10 patients treated by mechanical thrombectomy. Histological and immunohistochemical analysis was performed to determine clot composition. SBFSEM was used to assess the ultrastructural organization of the clots and specific features of individual components.

RESULTS

Quantification of Martius Scarlett Blue stain identified fibrin (44.4%) and red blood cells (RBCs, 32.6%) as the main components. Immunohistochemistry showed a mean platelet and von Willebrand factor content of 23.9% and 11.8%, respectively. The 3D organization of emboli varied greatly depending on the region analyzed. RBC-rich areas were composed mainly of tightly packed RBCs deformed into polyhedrocytes with scant fibrin fibers interwoven between cells. The regions with mixed composition showed thick fibrin fibers along with platelets, white blood cells and RBC clusters. Fibrin-rich areas contained dense fibrin masses with sparse RBC. In three cases, the fibrin formed a grid-like or a sponge-like pattern, likely due to thrombolytic treatment. Segmentation showed that fibrin fibers were thinner and less densely packed in these cases.

CONCLUSIONS

3D-SEM provides novel and potentially clinically relevant information on clot components and ultrastructure which may help to inform thrombolytic treatment and medical device design.

LncRNA BLACAT1 regulates the viability, migration and invasion of oral squamous cell carcinoma cells by targeting miR-142-5p

OBJECTIVE

Oral squamous cell carcinoma (OSCC) is one of the most common head and neck tumors with high incidence and mortality. Long noncoding RNA bladder cancer-associated transcript 1 (lncRNA BLACAT1) was involved in several cancers development. However, the roles of BLACAT1 in OSCC have not been investigated.

MATERIALS AND METHODS

The expressions of BLACAT1 and miR-142-5p in OSCC cells were measured by quantitative real-time polymerase chain reaction (qRT-PCR). Cell viability was evaluated by MTT assay. Cell migration and invasion were evaluated by transwell migration assay and transwell invasion assay, respectively. The protein levels of CyclinD1, p21, p27, MMP-2, MMP-9 and MMP-14 were detected by Western blot analysis. The interaction of BLACAT1 and miR-142-5p was verified by luciferase reporter assay.

RESULTS

The expression of BLACAT1 was increased and the expression of miR-142-5p was decreased in OSCC cells. The knockdown of BLACAT1 suppressed the viability, migration and invasion of OSCC cells. miR-142-5p was identified as a target of BLACAT1 and BLACAT1 overexpression suppressed miR-142-5p expression. Furthermore, overexpression of miR-142-5p showed similar effects on OSCC cells viability, migration and invasion with BLACAT1 knockdown, and inhibition of miR-142-5p restored the effects of BLACAT1 knockdown OSCC cells viability, migration and invasion.

CONCLUSIONS

LncRNA BLACAT1 knockdown suppressed the viability, migration and invasion of OSCC cells by sponging miR-142-5p, indicating that BLACAT1 might be a novel target for the treatment of OSCC.

Cellular responses to flow diverters in a tissue-engineered aneurysm model

BACKGROUND

Notwithstanding the widespread implementation of flow diverters (FDs) in the treatment of intracranial aneurysms, the exact mechanism of action of these devices remains elusive. We aimed to advance the understanding of cellular responses to FD implantation using a 3D tissue-engineered in vitro aneurysm model.

METHODS

Aneurysm-like blood vessel mimics (aBVMs) were constructed by electrospinning polycaprolactone nanofibers onto desired aneurysm-like geometries. aBVMs were seeded with human aortic smooth muscle cells (SMCs) followed by human aortic endothelial cells (ECs). FDs were then deployed in the parent vessel of aBVMs covering the aneurysm neck and were cultivated for 7, 14, or 28 days (n=3 for each time point). The EC and SMC coverage in the neck was measured semi-quantitatively.

RESULTS

At day 7, the device segment in contact with the parent vessel was partially endothelialized. Also, the majority of device struts, but not pores, at the parent vessel and neck interface were partially covered with ECs and SMCs, while device struts in the middle of the neck lacked cell coverage. At 14 days, histology verified a neointimal-like lining had formed, partially covering both the struts and pores in the center of the neck. At 28 days, the majority of the neck was covered with a translucent neointimal-like layer. A higher degree of cellular coverage was seen on the struts and pores at the neck at 28 days compared with both 7 and 14 days.

CONCLUSION

aBVMs can be a valuable alternative tool for evaluating the healing mechanisms of endovascular aneurysm devices.

Characterization of thrombus composition with multimodality CT-based imaging: an in-vitro study

BACKGROUND

CT is the most commonly used imaging modality for acute ischemic stroke evaluation. There is growing interest to use pre-operative imaging to characterize clot composition in stroke. We performed an in-vitro study examining the ability of various CT techniques in differentiation between different clot types.

METHODS

Five clot types with varying fibrin and red blood cells (RBCs) densities (5% RBC and 95% fibrin; 25% RBC and 75% fibrin; 50% RBC and 50% fibrin; 75% RBC and 25% fibrin; 95% RBC and 5% fibrin) were prepared and scanned using various CT scanning protocols (single-energy, dual-energy, photon-counting detector CT, mixed images, and virtual monoenergetic images). Martius Scarlett Blue trichrome staining was performed to confirm the composition of each clot. Mean CT values of each type of clot under different scanning protocol were calculated and compared.

RESULTS

Mean CT values of the CT numbers in the five clot specimens for 5%, 25%, and 50% RBC clot were similar across modalities, and increased significantly for 75% and 95% RBC clots (P<0.0001). Mean CT values are highest in the Mono +50 keV images in each type of clot, and they were also significantly higher than all other imaging protocols (P<0.001). Dual-energy CT with Mono +50 keV images showed the greatest difference between attenuation in each type of clot.

CONCLUSION

Mono +50 keV dual-energy CT scan may be helpful for differentiating between RBC-rich and fibrin-rich thrombi seen in large-vessel occlusion patients.

[Analysis on the relationship between smoking status and the onset age of onset and the direct medical expenditure expenses of gastric cancer patients]

Objective: To investigate the relationship between smoking status and the onset age of stomach cancer patients and estimate the patients' direct medical cost burden of stomach cancer due to smoking in Anhui province. Methods: The information about the primary stomach cancer patients and their direct treatment expenditures in 10 cancer-registered areas in Anhui were collected in 2017. The association between smoking status and the age of onset of stomach cancer patients was analyzed by univariate regression and multivariate logistic regression models. The median and smoking-attributed risk method was used to describe the direct treatment expenditure of stomach cancer patients in Anhui due to smoking. Results: A total of 736 patients with stomach cancer were analyzed in this study. Univariate regression analysis showed that rural household registration (t=2.091, P=0.037), smoking (t=-2.357, P=0.001 9) and alcohol consumption (t=-2.036, P=0.042) were related to the age of onset of stomach cancer. After adjusting for gender, alcohol consumption, body mass index and household registration type, the risk of early stomach cancer in people who quitted smoking cessation was lower than that in smokers (OR=0.36, 95%CI: 0.17-0.75). The total direct medical cost burden of 736 newly diagnosed stomach cancer patients was 6.939 6 million RMB. The direct medical expenditure in stomach cancer patients who had smoking behavior was higher than that in stomach cancer patients who quitted smoking and never smoked. Conclusions: Smoking is one of the risk factors for the earlier onset of stomach cancer in Anhui. It is necessary to strengthen tobacco control to reduce the economic burden of patients with stomach cancer.

[A cross-sectional study on the prevalence and related factors of dyslipidemia among adults in Anhui province, in 2015]

Objective: Based on the data of chronic diseases and nutrition surveillance among Chinese adults in 2015, dyslipidemia and related factors were analyzed. Methods: Multi-stage stratified cluster random sampling was used to select participants who were aged 18 and over, with questionnaire survey and related measurements conducted. Prevalence rates of dyslipidemia among participants by different characteristics and influencing factors were analyzed, using the method of complex weighting and post-weighted stratification. Results: In all, 7 404 participants were included. The overall prevalence of dyslipidemia was 30.5% among the adults. The overall prevalence of dyslipidemia were 36.5% in males and 24.4% in females (P<0.05). The prevalence rates of hypercholesterolemia, hypertriglyceridemia, high LDL-C, and low HDL-C were 3.7%, 12.2%, 5.3%, and 19.4%, respectively. Results from the multivariate logistic regression model analysis showed that age (OR=1.009, 95%CI: 1.000-1.018), female (OR=0.501, 95%CI: 0.397-0.632), College degree or above (OR=1.728, 95%CI: 1.257-2.374), alcohol consumption 3 (OR=0.711, 95%CI: 0.536-0.943), central obesity (OR=1.868, 95%CI: 1.547-2.257), BMI (OR=1.141, 95%CI: 1.098-1.186), hypertension (OR=1.259, 95%CI: 1.077-1.473) and diabetes (OR=2.025, 95%CI: 1.446-2.835) were influencing factors on dyslipidemia. Conclusions: The prevalence of dyslipidemia seemed high among adults in Anhui. Risk factors should be closely monitored and under control, including those people with unhealthy lifestyles or being overweight, obesity, hypertensive and diabetic.

[Prevalence and risk factors of ischemic stroke in rural areas of Liaoning province]

Objective: To explore the prevalence and risk factors of ischemic stroke in rural areas of Liaoning province. Methods: The study was a cross-sectional survey. From September 2017 to May 2018, a total of 10 926 rural residents aged ≥40 years were investigated in Chaoyang county, Lingyuan, Liaoyang county and Donggang city of Liaoning province. The investigation included questionnaire survey, physical examination and laboratory examination.Univariate and multivariate logistic regression models were used to analyze the risk factors of ischemic stroke. Results: The prevalence of ischemic stroke in the rural areas of Liaoning province was 5.51% (602/10 926), and the standardized prevalence rate was 4.04%. The standardized prevalence rate of male (5.05%) is higher than that of female (3.44%). The prevalence of ischemic stroke increased with age in both males (P<0.01) and females (P<0.01). Multivariate logistic regression analysis showed that age increase(compared with 40-49 years old group, 50-59 years old, OR=2.08, 95%CI 1.31-3.30, P=0.02; 60-69 years old, OR=3.90, 95%CI 2.51-6.05, P<0.01; 70-79 years old, OR=5.32, 95%CI 3.37-8.34, P<0.01; ≥80 years old, OR=3.64, 95%CI 2.00-6.62, P<0.01), male(OR=2.35, 95%CI 1.95-2.84, P<0.01),family history of stroke(OR=2.18, 95%CI 1.83-2.60, P<0.01),coronary heart disease (OR=2.01, 95%CI 1.52-2.66, P<0.01), hypertension (OR=2.82, 95%CI 2.21-3.60, P<0.01), diabetes mellitus (OR=1.36, 95%CI 1.11-1.67, P=0.03) and overweight/obese (OR=1.22, 95%CI 1.02-1.47, P=0.03) were the major risk factors of ischemic stroke. Conclusions: The prevalence of ischemic stroke in rural areas of Liaoning province is high. Age, male, family history of stroke, coronary heart disease, hypertension, diabetes mellitus, overweight/obesity are the risk factors of ischemic stroke in rural areas of Liaoning province.

Abstract WP268: Von Willebrand Factor Expression in Various Subtypes of Acute Ischemic Stroke

Introduction: Von Willebrand factor (VWF) is a key component of acute ischemic stroke (AIS) thrombi. The aim of our prospective study was to investigate the immunohistochemical expression of VWF in clots and to evaluate whether VWF is associated with certain subtypes of AIS.

Methods: VWF immunostaining was performed on 79 thrombi collected as part of the multi-center Stroke Thromboembolism Registry of Imaging and Pathology (STRIP) registry. The cases were classified according to TOAST criteria. The VWF expression was quantified using Orbit Image Analysis (www.Orbit.bio) machine learning software. IBM SPSS statistics 25 was used to assess the relationship between the VWF levels and different etiology subtypes.

Results: A cardioembolic stroke was defined in 39 cases (49.4%) whereas an atherosclerotic origin was identified in 13 patients (16.5%). Other causes accounted for 12 cases (15.1%). Unknown etiology was reported in 15 cases (19%). The mean VWF content in the clots was 12.8%. According to the Mann-Whitney U-test, the level of VWF was significantly higher in the cases with unknown etiology compared to cardioembolic origin (p=0.044). We found also that patients with unknown etiology of stroke had higher VWF expression as compared to the other two subtypes, although this difference was not statistically significant.

Conclusions: Among the patients with ischemic stroke included in this study, the VWF expression was significantly increased in those with unknown etiology compared to the group with cardioembolic stroke. Our finding provides new insights into clot composition in cryptogenic stroke and may influence the treatment and secondary prevention in these cases.

Abstract TP214: 3D-Electron Microscopy for the Analysis of the Microstructure of Acute Ischemic Stroke Clots

Introduction: Characterization of acute ischemic stroke thrombi has typically focused on the two dimensional (2D) histological characterization of the thrombus. Little is known about the three dimensional (3D) structure of these occlusive thrombi. Electron Microscopy (EM) can be used to obtain 3D information about the organization of clot components. Individual structures can be segmented and qualitative and quantitative information obtained from the clots.

Methods: Following IRB approval from Mayo Clinic, acute ischemic stroke clot samples were collected from 10 patients treated at Mayo Clinic. Samples were immediately fixed in fresh modified Trumps fixative solution. A representative fragment of clot was taken and split longitudinally into two pieces; one piece was sent for 3D-EM analysis and the other for histological processing and analysis. Hematoxylin and eosin stain (H&E) and Martius Scarlett Blue (MSB) histological stains were used for conventional histopathology evaluation and components analysis. Immunohistochemical (IHC) staining using anti-CD42b (Platelets) was applied to confirm the presence of platelets in each clot. Serial block-face scanning electron microscopy was used to generate high-resolution three-dimensional images.

Results: The 2D morphological features of the clot were identified using H&E, MSB and anti-CD42b staining. The 3D organization of thrombi varies greatly, both within and between clots depending on the constituents. Red Blood Cell-rich areas are mainly composed of Red Blood Cells packaged tightly together, with a small number of Fibrin strands interwoven between the cells. Fibrin-rich areas are characterized by dense networks of fibrin strands along with platelets and White Blood Cells with some sparse Red Blood Cells present. Platelet-rich areas are composed of large volumes of de-granulated platelets, some fibrin stands and white blood cells and an absence of Red Blood Cells.

Conclusions: 3D electron microscopy can provide important information on the organization of components within thrombi. This could provide key information on the age and etiology of the thrombus. In addition, it may help to inform thrombolytic treatment and medical device design.

Abstract WP108: Novel Human Acute Ischemic Stroke Blood Clot Analogues for in-vitro Testing

Introduction: Previous studies have successfully created blood clot analogues for In-vitro testing using animal blood. Blood components vary greatly among species and thus, creating clot analogues with human blood is likely a more accurate representation of thrombi formed in the human vasculature. We present a novel method of creating clot analogues from human blood and platelets that mimic the process by which clots form In-vivo .

Methods: Following IRB approval from Mayo Clinic, human whole blood and platelets donations were obtained from the Blood Transfusion service. The whole blood was centrifuged at 1,200RPM for 20 minutes to separate it into its constituents. Plasma was removed and the remaining Red Blood Cells and Buffy Coat were mixed together by inverting. A total of 12 clot analogues were created with varying concentrations of components; Red Blood cells/Buffy Coat, Plasma and Platelets. Thrombin was added first to stimulate platelets activation for a total of 5 mins whilst continuously mixing by inversion. The RBC/WBC mixture was added next followed by CaCl2. The mixture was then quickly drawn into a 3cc syringe and spun overnight at 20RPM at room temperature to mimic dynamic flow conditions. Macro-photographs were taken to display the variation in texture and color between different clot analogue types. The clots were then fixed in 10% neutral buffered formalin for 24 hours prior to being processed. Histopathological analysis was performed using Hematoxylin and Eosin (H&E) and Martius Scarlet Blue (MSB) staining to confirm clot composition.

Results: Red Blood cell-rich, Fibrin-rich, Platelet-rich and mixed clot analogues that accurately mimic clots retrieved from Acute Ischemic Stroke Patients were created. The range of histopathological compositions of the clot analogues is similar to that of the clinical samples.

Conclusions: The addition and activation of platelets is key to creating accurate clot analogues for In-vitro testing. Spinning the clots is important to prevent natural sedimentation and mimic the In-vivo situation.

Orbit image analysis machine learning software can be used for the histological quantification of acute ischemic stroke blood clots

Our aim was to assess the utility of a novel machine learning software (Orbit Image Analysis) in the histological quantification of acute ischemic stroke (AIS) clots. We analyzed 50 AIS blood clots retrieved using mechanical thrombectomy procedures. Following H&E staining, quantification of clot components was performed by two different methods: a pathologist using a reference standard method (Adobe Photoshop CC) and an experienced researcher using Orbit Image Analysis. Following quantification, the clots were categorized into 3 types: RBC dominant (≥60% RBCs), Mixed and Fibrin dominant (≥60% Fibrin). Correlations between clot composition and Hounsfield Units density on Computed Tomography (CT) were assessed. There was a significant correlation between the components of clots as quantified by the Orbit Image Analysis algorithm and the reference standard approach (ρ = 0.944**, p < 0.001, n = 150). A significant relationship was found between clot composition (RBC-Rich, Mixed, Fibrin-Rich) and the presence of a Hyperdense artery sign using the algorithmic method (X2(2) = 6.712, p = 0.035*) but not using the reference standard method (X2(2) = 3.924, p = 0.141). Orbit Image Analysis machine learning software can be used for the histological quantification of AIS clots, reproducibly generating composition analyses similar to current reference standard methods.

Clot permeability and histopathology: is a clot's perviousness on CT imaging correlated with its histologic composition?

BACKGROUND

Clot perviousness in large vessel occlusion has been shown to be associated with improved recanalization outcomes with mechanical thrombectomy and intravenous thrombolysis.

OBJECTIVE

To evaluate the association between clot perviousness based on thrombus attenuation increase (TAI) on CT, and histologic composition of clots in acute ischemic stroke (AIS).

METHODS

A retrospective review was completed of patients with AIS secondary to large vessel occlusion, non-contrast CT (NCCT) and CT angiography (CTA) images, and histologic analysis of the retrieved clot. TAI was measured by subtracting clot attenuation on NCCT from the attenuation on CTA. Up to 3 regions of interest (ROIs) were evaluated on each clot; the average attenuation was used for analysis if multiple ROIs were assessed. Pervious clots were defined as TAI ≥10 Hounsfield units (HUs); impervious clots had TAI <10 HU. Histopathologic analyses of clots were assessed for relative compositions of red blood cells (RBCs), white blood cells (WBCs), fibrin, and platelets/other.

RESULTS

57 patients were included. Pervious clots were more likely to be RBC rich (p=0.04); impervious clots were more likely to be fibrin and WBC rich (p=0.01 for both). Pervious clots also had greater RBC density than impervious clots (49.8% and 33.0%, respectively; p=0.006); fibrin density of pervious clots was lower than that of impervious clots (17.8% and 23.2%, respectively; p=0.02).

CONCLUSION

Clot perviousness, assessed on NCCT and CTA imaging, is associated with higher RBC density and lower fibrin density, offering a possible explanation for the higher rates of successful thrombectomy and favorable clinical outcome seen in such patients.

NanoARG: a web service for detecting and contextualizing antimicrobial resistance genes from nanopore-derived metagenomes

BACKGROUND

Direct and indirect selection pressures imposed by antibiotics and co-selective agents and horizontal gene transfer are fundamental drivers of the evolution and spread of antibiotic resistance. Therefore, effective environmental monitoring tools should ideally capture not only antibiotic resistance genes (ARGs), but also mobile genetic elements (MGEs) and indicators of co-selective forces, such as metal resistance genes (MRGs). A major challenge towards characterizing the potential human health risk of antibiotic resistance is the ability to identify ARG-carrying microorganisms, of which human pathogens are arguably of greatest risk. Historically, short reads produced by next-generation sequencing technologies have hampered confidence in assemblies for achieving these purposes.

RESULTS

Here, we introduce NanoARG, an online computational resource that takes advantage of the long reads produced by nanopore sequencing technology. Specifically, long nanopore reads enable identification of ARGs in the context of relevant neighboring genes, thus providing valuable insight into mobility, co-selection, and pathogenicity. NanoARG was applied to study a variety of nanopore sequencing data to demonstrate its functionality. NanoARG was further validated through characterizing its ability to correctly identify ARGs in sequences of varying lengths and a range of sequencing error rates.

CONCLUSIONS

NanoARG allows users to upload sequence data online and provides various means to analyze and visualize the data, including quantitative and simultaneous profiling of ARGs, MRGs, MGEs, and putative pathogens. A user-friendly interface allows users the analysis of long DNA sequences (including assembled contigs), facilitating data processing, analysis, and visualization. NanoARG is publicly available and freely accessible at https://bench.cs.vt.edu/nanoarg .

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.

Platelet-Rich Emboli in Cerebral Large Vessel Occlusion Are Associated With a Large Artery Atherosclerosis Source

Background and Purpose- Nearly 30% of large vessel occlusion acute ischemic stroke clots are from an unknown source. We assessed histological clot composition in a series of patients with large vessel occlusion and investigated correlations between clot composition and stroke pathogenesis. Methods- As part of the multi-institutional STRIP registry (Stroke Thromboembolism Registry of Imaging and Pathology), consecutive emboli retrieved during mechanical thrombectomy were stained using Martius Scarlett Blue and analyzed using machine learning software. We assessed proportions of red blood cells, fibrin, platelets, and white blood cells. Correlations between clot components and stroke pathogenesis (large artery atherosclerosis, cardioembolism, and stroke of undetermined pathogenesis) were assessed using SPSS22. Results- One hundred five patients were included. The proportion of platelet-rich clots (55.0% versus 21.2%; P=0.005) and percentage of platelet content (22.1±4.2% versus 13.9±14.2%; P=0.03) was significantly higher in the large artery atherosclerosis group compared with the cardioembolic group. The proportion of platelet-rich clots (50.0% versus 21.2%; P=0.024) was also significantly higher in the cryptogenic group compared with cardioembolic cases. Large artery atherosclerosis and cryptogenic cases had a similar proportion of platelet-rich clots (55.0% versus 50.0%; P=0.636). There was no significant difference between stroke pathogenesis and the other major clot components. Conclusions- High platelet content of emboli is associated with a large artery atherosclerosis etiology of large vessel occlusion.