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

Emerging Adjuvant Thrombolytic Therapies for Acute Ischemic Stroke Reperfusion

Thrombolytic therapies for acute ischemic stroke are widely available but only result in recanalization early enough, to be therapeutically useful, in 10% to 30% of cases. This large gap in treatment effectiveness could be filled by novel therapies that can increase the effectiveness of thrombus clearance without significantly increasing the risk of harm. This focused update will describe the current state of emerging adjuvant treatments for acute ischemic stroke reperfusion. We focus on new treatments that are designed to (1) target different components that make up a stroke thrombus, (2) enhance endogenous fibrinolytic systems, (3) reduce stagnant blood flow, and (4) improve recanalization of distal thrombi and postendovascular thrombectomy.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Characteristics and prognostic impact of unsuccessful recanalization after endovascular therapy for acute ischemic stroke

BACKGROUND

Endovascular therapy (EVT) has shown high therapeutic efficacy for acute large vessel occlusion (LVO); however, recanalization is unsuccessful in some cases. This study aimed to examine the characteristics and prognostic impact of unsuccessful recanalization after EVT compared with medical treatment alone.

METHODS

We conducted a post hoc analysis of RESCUE-Japan Registry 2, a nationwide registry of 2408 consecutive patients with acute LVO. Patients without successful recanalization after EVT (thrombolysis in cerebral infarction grade ≤ 2a) were classified into the Unsuccessful EVT group, and compared with the No-EVT group. To account for selection bias, the outcomes were compared in a propensity score-matched cohort. The outcomes included the modified Rankin Scale (mRS) score at 90 days and intracranial hemorrhage within 72 h after the LVO onset.

RESULTS

Among 188 (14.7 %) patients in the Unsuccessful EVT group out of 1281 who underwent EVT, 147 were matched with the No-EVT group, with comparable baseline characteristics. Patients in the Unsuccessful EVT group had a higher distribution of mRS score at 90 days and were less likely to achieve mRS 0-2 compared to those in the No-EVT group (23 % vs. 34 %, OR:0.58, 95 % CI:0.35-0.98). All-cause mortality was higher in the Unsuccessful EVT group (16 % vs. 6.8 %, OR: 2.54, 95 % CIs: 1.16-5.55). Symptomatic intracranial hemorrhage was more frequently observed in the Unsuccessful EVT group (5.4 % vs. 0.7 %, OR: 8.40, 95 % CIs: 1.04-68.1).

CONCLUSIONS

The clinical outcomes of patients without successful recanalization after EVT were worse than those who did not undergo EVT.

Association between thrombus composition and first-pass recanalization after thrombectomy in acute ischemic stroke

BACKGROUND

Achieving first-pass recanalization (FPR) has become the primary procedural objective during thrombectomy in acute ischemic stroke patients as it correlates with the best clinical outcome. Understanding factors contributing to FPR failures is essential to enhance FPR success rates. As the central target of thrombectomy, the thrombus itself may be a significant factor influencing FPR.

OBJECTIVES

This study aimed to investigate the association between thrombus composition and FPR success rates.

METHODS

In total, thrombi from 267 ischemic stroke patients were collected in the AZ Groeninge Hospital (Kortrijk, Belgium). Thrombus composition was determined via detailed histologic analysis of red blood cells (RBCs), fibrin, von Willebrand factor, platelets, leukocytes, citrullinated histone 3 (marker for neutrophil extracellular traps), and intracellular and extracellular DNA. FPR was defined as obtaining a modified thrombolysis in cerebral infarction (mTICI) score of 2c/3 after the first pass.

RESULTS

An mTICI score of 2c/3 was obtained in 180 patients, which was achieved via a successful FPR procedure in 126 cases or after multiple passes in 54 cases. Interestingly, thrombi from FPR cases had a different composition from thrombi that needed multiple passes to obtain an mTICI score of 2c/3. FPR thrombi contained significantly more RBCs (P = .0264), less fibrin (P = .0196), and less extracellular DNA (P = .0457).

CONCLUSION

Our results indicate that thrombi characterized by lower RBC content, higher fibrin levels, and increased extracellular DNA are less likely to result in an FPR. These results are important to guide future research aiming at improving procedures or technologies to obtain FPR rates in RBC-poor thrombi.

Evaluation of partial resheathing of EmboTrap III using the microcatheter (PREMIER) technique for fibrin-rich hard clots in an in vitro vessel model

Background and purpose

Despite the ongoing advancements in mechanical thrombectomy for large vessel occlusions causing acute ischemic stroke, successful recanalization is not achieved in all patients. One contributing factor is the presence of fibrin-rich hard clots. We proposed a new technique called the PREMIER technique, which aims to retrieve fibrin-rich clots. This study evaluated the efficacy of the PREMIER technique on fibrin-rich and erythrocyte-rich clots by comparing it with the simple use of EmboTrap III in an in vitro vessel model.

Methods

The PREMIER technique involves partially resheathing a fully deployed EmboTrap III (CERENOVUS, Johnson & Johnson Medical Devices, Irvine, California, USA) using a microcatheter to capture and retrieve a hard clot between the inner channel and outer cages of EmboTrap III. We compared recanalization rate of the PREMIER technique with the simple use of EmboTrap III in an in vitro vessel model, occluding the M1 segment with fibrin-rich hard clots (0% erythrocyte composition) and erythrocyte-rich clots (50% erythrocyte composition).

Results

Among the 40 procedures (10 each for the PREMIER technique and the simple use of EmboTrap III for two different clots) for fibrin-rich clots, the PREMIER technique achieved successful recanalization in all 10 cases, with a significantly higher recanalization rate than the EmboTrap III (100% vs. 50%, p = 0.03). For erythrocyte-rich clots, the recanalization rate was not significantly different in the PREMIER technique compared with the simple use of EmboTrap III (80% vs. 70%, p = 1.00).

Conclusion

The PREMIER technique is a novel technique for acute large-vessel occlusions caused by fibrin-rich hard clots that hinders successful recanalization during mechanical thrombectomy.

Comparison of Outcomes between Stent Retriever Combined with Contact Aspiration and Contact Aspiration Alone in Patients without Hyperdense Artery Sign/Susceptibility Vessel Sign

PURPOSE

To examine the relationship between hyperdense artery sign (HAS)/susceptibility vessel sign (SVS) and thrombus composition and evaluate the effect of HAS/SVS status on the association between first-line thrombectomy techniques and outcomes in patients with acute anterior circulation large vessel occlusion (LVO).

MATERIALS AND METHODS

From January 2018 to June 2021, 103 consecutive patients with acute anterior circulation LVO (75 [63.1%] men; median age, 66 years) who underwent thrombectomy and for whom the removed clot was available for histological analyses were retrospectively reviewed. The presence of HAS and SVS was assessed on unenhanced computed tomography (CT) and susceptibility-weighted imaging, respectively. Association of first-line thrombectomy techniques (stent retriever [SR] combined with contact aspiration [CA] vs CA alone) with outcomes was assessed according to HAS/SVS status.

RESULTS

Among the included patients, 55 (53.4%) were HAS/SVS-negative, and 69 (67.0%) underwent first-line SR + CA. Higher relative densities of fibrin/platelets (0.56 vs 0.51; P < .001) and lower relative densities of erythrocytes (0.32 vs 0.42; P < .001) were observed in HAS/SVS-negative patients compared with HAS/SVS-positive patients. First-line SR + CA was associated with reduced odds of distal embolization (adjusted odds ratio, 0.18; 95% CI, 0.04-0.83; P = .027) and a more favorable 90-day functional outcome (adjusted odds ratio, 5.29; 95% CI, 1.06-26.34; P = .042) in HAS/SVS-negative patients and a longer recanalization time (53 vs 25 minutes; P = .025) and higher risk of subarachnoid hemorrhage (24.2% vs 0%; P = .044) in HAS/SVS-positive patients.

CONCLUSIONS

Absence of HAS/SVS may indicate a higher density of fibrin/platelets in the thrombus, and first-line SR + CA yielded superior functional outcomes than CA alone in patients with acute LVO without HAS/SVS.

Relationship between thrombus composition and prognosis in patients with acute ischemic stroke undergoing mechanical thrombectomy

BACKGROUND

Mechanical thrombectomy has emerged as the primary endovascular treatment for acute ischemic stroke. Numerous studies have investigated the relationship between thrombus composition and factors such as pharmacological thrombolysis, stroke etiology, mechanical thrombectomy, and radiological imaging. However, limited research has explored the association between thrombus composition and clinical outcomes.

METHODS

This retrospective analysis examined the histopathological examination of thrombi retrieved from 50 patients with acute ischemic stroke between May 2020 and May 2023. The composition of the retrieved thrombi was assessed using HE staining to quantify the proportions of red blood cells, white blood cells, platelets, and fibrin. Based on the predominant composition of the thrombus, the patients were divided into two groups: erythrocyte-rich and fibrin-rich. Demographics, clinical characteristics, and clinical outcomes assessed by the National Institutes of Health Stroke Scale (NIHSS) score and modified Rankin Scale (mRS) scores were collected retrospectively.

RESULT

Of the 50 patients, 23 were classified in the erythrocyte-rich group, and 27 were classified in the fibrin-rich group. There were no significant differences between the two groups in terms of age, sex, stroke subtype, history of hypertension and diabetes, thrombus location, NIHSS scores, mRS scores on admission, the time interval from symptom onset to hospitalization and reperfusion, or the rate of successful reperfusion. However, erythrocyte-rich thrombi were associated with a shorter time interval from puncture to reperfusion. No significant differences were found in the red blood cell fraction and fibrin/platelet fraction between large artery atherosclerosis and cardioembolism. At the 90-day follow-up, patients with erythrocyte-rich thrombi exhibited lower NIHSS scores and more favorable functional outcomes (mRS scores of 0-2) compared to those with fibrin-rich thrombi.

CONCLUSION

Erythrocyte-rich thrombi were linked to shorter time intervals from puncture to reperfusion and favorable clinical outcomes in patients with acute ischemic stroke. The composition of the thrombus may influence the thrombectomy strategy for endovascular therapy.

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.

Safety and efficacy of stent retrievers plus contact aspiration in patients with acute ischaemic anterior circulation stroke and positive susceptibility vessel sign in France (VECTOR): a randomised, single-blind trial

BACKGROUND

Positive susceptibility vessel sign (SVS) in patients with acute ischaemic stroke has been associated with friable red blood cell-rich clots and more effective recanalisation using stent retrievers versus contact aspiration. We compared the safety and efficacy of stent retrievers plus contact aspiration (combined technique) versus contact aspiration alone as the first-line thrombectomy technique in patients with acute ischaemic anterior circulation stroke and SVS-positive occlusions.

METHODS

Adaptive Endovascular Strategy to the Clot MRI in Large Intracranial Vessel Occlusion (VECTOR) was a prospective, randomised, open-label study with blinded evaluation. Patients with SVS-positive anterior circulation occlusions on pretreatment MRI and arterial puncture within 24 h of symptom onset were enrolled from 22 centres in France. A centralised web-based method was used by interventional neuroradiologists for dynamic randomisation by minimisation. Patients were randomly assigned 1:1 to the combined technique or contact aspiration alone. The primary outcome was expanded Thrombolysis in Cerebral Infarction (eTICI) grade 2c or 3 reperfusion after three or fewer passes on post-treatment angiogram, adjudicated by a blinded independent central imaging core laboratory. The intention-to-treat population was used to assess the primary and secondary outcomes. This trial is registered with ClinicalTrials.gov (NCT04139486) and is complete.

FINDINGS

Between Nov 26, 2019, and Feb 14, 2022, 526 patients were enrolled, of whom 521 constituted the intention-to-treat population (combined technique, n=263; contact aspiration alone, n=258). The median age of participants was 74·9 years (IQR 64·4-83·3); 284 (55%) were female and 237 (45%) male. The primary outcome did not differ significantly between groups (152 [58%] of 263 patients for the combined technique vs 135 [52%] of 258 for contact aspiration; odds ratio [OR] 1·27; 95% CI 0·88-1·83; p=0·19). Procedure-related adverse events occurred in 32 (12%) of 263 patients in the combined technique group and 27 (11%) of 257 in the contact aspiration group (OR 1·14; 0·65-2·00; p=0·65). The most common adverse event was intracerebral haemorrhage (146 [56%] of 259 patients for the combined technique vs 123 [49%] of 251 for contact aspiration; OR 1·32; 0·91-1·90; p=0·13). All-cause mortality at 3 months occurred in 57 (23%) of 251 patients in the combined technique group and 48 (19%) of 247 in the contact aspiration group (OR 1·19; 0·76-1·86; p=0·45), none of which was treatment-related.

INTERPRETATION

The results of the VECTOR trial do not show superiority of the combined stent retriever plus contact aspiration technique over contact aspiration alone in patients with SVS-positive occlusion with respect to achieving eTICI 2c-3 within three passes. These findings support the use of either the combined technique or contact aspiration alone as the initial thrombectomy strategy in patients with acute anterior circulation stroke with SVS on pretreatment MRI.

FUNDING

Cerenovus.

Thrombus histology does not predict stroke etiological subtype but influences recanalization

BACKGROUND

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

METHODOLOGY

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

RESULTS

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

CONCLUSION

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

Exploring thrombus composition in cerebral venous thrombosis: the first case report with initial insights and implications for treatment advancements

BACKGROUND

Endovascular thrombectomy (EVT) is a treatment option in patients with a cerebral venous thrombosis (CVT) who deteriorate despite anticoagulant treatment. Assessment of thrombus composition in CVT may provide insights into the pathophysiology of the disease and suggest new therapeutic strategies.

CASE REPORT

A 47-year-old woman (smoking habit and estradiol/progesterone-releasing intra-uterine device) diagnosed with massive CVT underwent EVT (complete recanalization via aspiration catheter and stentriever) due to acute-onset left-sided weakness and dysarthria despite 72 h of full-dose subcutaneous low-molecular heparin. Two main reddish clots (maximum diameter 15 mm) were retrieved. Microscopic assessment showed an erythrocyte-rich thrombus (83.9% of entire thrombus surface) with layers of platelets/fibrin (lines of Zahn: 13.9% fibrin and 38.5% platelet [CD61+]). The immunological profile was dominated by neutrophils (30% MPO+), with neutrophil extracellular traps (NETs) in 1.9% of thrombus surface. T- (CD3+), B-lymphocytes (CD20+), and monocytes/macrophages (CD68+) were rather rare (2.2%, 0.7%, and 2.0% respectively). We found no evidence (0.0%) of hemosiderin and endothelial cells (CD34+). Full clinical recovery occurred prior to discharge.

CONCLUSION

This is the first case report of a CVT with histologic assessment of the thrombus retrieved via EVT. Evaluating thrombi in CVT can provide key insights into disease pathophysiology and guide treatment advancements.

R-tPA Resistance Is Specific for Platelet-Rich Stroke Thrombi and Can Be Overcome by Targeting Nonfibrin Components

BACKGROUND

Resistance to r-tPA (recombinant tissue-type plasminogen activator) is a well-known but poorly understood phenomenon that hampers successful recanalization in patients with acute ischemic stroke. Using clinically relevant thrombi from patients with acute ischemic stroke, we investigated if and how thrombus composition impacts r-tPA-mediated lysis. In addition, we explored strategies to overcome r-tPA resistance.

METHODS

Thrombi were split into 2 parts, 1 of which was used for thrombolysis and the other for detailed histological analysis. Thrombolysis was performed in normal human plasma using r-tPA alone, using r-tPA in combination with DNase-1 or using r-tPA in combination with N,N'-diacetyl-l-cystine. Thrombus lysis was calculated as the percentage of residual thrombus weight compared with its initial weight and the degree of lysis was linked to thrombus composition determined via histology.

RESULTS

Interestingly, we found that the efficacy of r-tPA-mediated thrombolysis was strongly correlated with the composition of the thrombi. Thrombi containing high amounts of red blood cells and low amounts of DNA and von Willebrand Factor were efficiently degraded by r-tPA, whereas thrombi containing low amounts of red blood cells and higher amounts of DNA and von Willebrand Factor were resistant to r-tPA. Importantly, combination of r-tPA with DNase-1 or N,N'-diacetyl-l-cystine significantly and specifically improved the lysis of these r-tPA-resistant thrombi.

CONCLUSIONS

Using patient thrombus material, our results for the first time show that the composition of stroke thrombi largely determines their susceptibility to r-tPA-mediated thrombolysis. Red blood cell-poor thrombi have a specific resistance to r-tPA, which can be overcome by targeting nonfibrin components using DNase-1 or N,N'-diacetyl-l-cystine.

Histone content, and thus DNA content, is associated with differential in vitro lysis of acute ischemic stroke clots

BACKGROUND

Fibrin, von Willebrand factor, and extracellular DNA from neutrophil extracellular traps all contribute to acute ischemic stroke thrombus integrity.

OBJECTIVES

In this study, we explored how the proteomic composition of retrieved thromboemboli relates to susceptibility to lysis with distinct thrombolytics.

METHODS

Twenty-six retrieved stroke thromboemboli were portioned into 4 segments, with each subjected to 1 hour of in vitro lysis at 37 °C in 1 of 4 solutions: tissue plasminogen activator (tPA), tPA + von Willebrand factor-cleaving ADAMTS-13, tPA + DNA-cleaving deoxyribonuclease (DNase) I, and all 3 enzymes. Lysis, characterized by the percent change in prelysis and postlysis weight, was compared across the solutions and related to the corresponding abundance of proteins identified on mass spectrometry for each of the thromboemboli used in lysis.

RESULTS

Solutions containing DNase resulted in approximately 3-fold greater thrombolysis than that with the standard-of-care tPA solution (post hoc Tukey, P < .01 for all). DNA content was directly related to lysis in solutions containing DNase (Spearman's ρ > 0.39 and P < .05 for all significant histones) and inversely related to lysis in solutions without DNase (Spearman's ρ < -0.40 and P < .05 for all significant histones). Functional analysis suggests distinct pathways associated with susceptibility to thrombolysis with tPA (platelet-mediated) or DNase (innate immune system-mediated).

CONCLUSION

This study demonstrates synergy of DNase and tPA in thrombolysis of stroke emboli and points to DNase as a potential adjunct to our currently limited selection of thrombolytics in treating acute ischemic stroke.

Optimizing catheter centering enhances mechanical thrombectomy success: Performance difference in cases using novel macrowires versus traditional microwires

BACKGROUND

The aim of this study is to determine how guidewire selection impacts procedure time and success and analyze if the trend toward the adoption of larger diameter guidewires provides a quantifiable advantage over traditional 0.014″ guidewires.

METHODS

A review of 494 consecutively performed acute ischemic stroke cases performed between 2018 and 2022 were reviewed and grouped into cases using a single 0.014″ outer diameter (OD) guidewire (195 cases) and cases using a single 0.018″ or 0.024″ OD guidewire (128 cases). These groups were compared for differences in average time to recanalization, average number of passes to achieve recanalization, and first pass success. Cases were compared overall, and further analyzed by region of occlusion to look at specific guidewire related differences for cases with M1, M2, and ICA occlusions.

RESULTS

Procedures using a larger OD guidewire have an average 5 min and 30 s reduction in time from puncture to recanalization (p = 0.0201). ICA occlusion cases using a larger macrowire show a 20 min reduction in recanalization time (p = 0.0005), a reduction in average number of passes from 2.6 to 1.7 (p = 0.0058), and an increase in first pass success from 18.8% to 58.3% when compared to traditional guidewires.

CONCLUSION

Large 0.018″ or 0.024″ OD guidewires better fill the lumen of the catheter and help to center the thrombectomy system in the vessel and navigate to the clot face. This leads to a reduction in procedure time and number of passes, and an increase in first pass success, especially when treating occlusions in the ICA.

Dual-Energy Computed Tomography Virtual Noncalcium Imaging of Intracranial Arteries in Acute Ischemic Stroke: Differentiation Between Acute Thrombus and Calcification

OBJECTIVE

Hyperdense artery sign (HAS) on noncontrast brain computed tomography (CT) indicates an acute thrombus within the cerebral artery. It is a valuable imaging biomarker for diagnosing large-vessel occlusion; however, its identification may be challenging with the presence of vascular calcification. Dual-energy CT virtual noncalcium (VNCa) imaging using a 3-material decomposition algorithm is helpful for differentiating between calcification and hemorrhage. This study aimed to clarify the potential of VNCa imaging for differentiating HAS from vascular calcification.

METHODS

Patients with acute ischemic stroke and large-vessel occlusion identified on MR angiography, who also underwent noncontrast dual-energy CT, were included. The 80 kV/Sn 140 kV mixed images, with a weighting factor of 0.4, were considered 120 kVp-equivalent images. Postprocessing using a 3-material decomposition algorithm to differentiate between calcium (Ca), cerebrospinal fluid, and hemorrhage was performed via a commercially available 3-dimensional workstation. A mixed image, VNCa image, color-coded Ca image, and color-coded Ca image with VNCa image overlay (color-coded Ca-overlay image) were obtained, and axial reconstruction with a 1-mm slice thickness was performed for each image type. Two experienced neuroradiologists conducted imaging evaluations in consensus.

RESULTS

Thirty-four patients (mean age, 76.0 years; 21 male and 13 female patients) were included. The mixed and VNCa images revealed an HAS (indicating an acute clot) corresponding to the large-vessel occlusion site in 30 patients. Among them, the VNCa and color-coded Ca-overlay images enabled clear differentiation between the acute thrombus and adjacent vessel wall calcification in 5 patients. Among the other 4 patients, the VNCa, Ca-overlay, and Ca images identified calcified cerebral emboli in the M1 segment in 1 patient. For the other 3 patients, no high attenuation corresponding to magnetic resonance angiography findings was observed in any of the mixed, VNCa, Ca-overlay, or Ca images.

CONCLUSIONS

VNCa and color-coded Ca-overlay images obtained via dual-energy brain CT enabled differentiation of acute thrombus from vessel wall calcification and calcified cerebral emboli in patients with acute ischemic stroke.

Clot composition and recanalization outcomes in mechanical thrombectomy

BACKGROUND

Mechanical thrombectomy (MT) has become standard for large vessel occlusions, but rates of complete recanalization are suboptimal. Previous reports correlated radiographic signs with clot composition and a better response to specific techniques. Therefore, understanding clot composition may allow improved outcomes.

METHODS

Clinical, imaging, and clot data from patients enrolled in the STRIP Registry from September 2016 to September 2020 were analyzed. Samples were fixed in 10% phosphate-buffered formalin and stained with hematoxylin-eosin and Martius Scarlett Blue. Percent composition, richness, and gross appearance were evaluated. Outcome measures included the rate of first-pass effect (FPE, modified Thrombolysis in Cerebral Infarction 2c/3) and the number of passes.

RESULTS

A total of 1430 patients of mean±SD age 68.4±13.5 years (median (IQR) baseline National Institutes of Health Stroke Scale score 17.2 (10.5-23), IV-tPA use 36%, stent-retrievers (SR) 27%, contact aspiration (CA) 27%, combined SR+CA 43%) were included. The median (IQR) number of passes was 1 (1-2). FPE was achieved in 39.3% of the cases. There was no association between percent histological composition or clot richness and FPE in the overall population. However, the combined technique resulted in lower FPE rates for red blood cell (RBC)-rich (P<0.0001), platelet-rich (P=0.003), and mixed (P<0.0001) clots. Fibrin-rich and platelet-rich clots required a higher number of passes than RBC-rich and mixed clots (median 2 and 1.5 vs 1, respectively; P=0.02). CA showed a trend towards a higher number of passes with fibrin-rich clots (2 vs 1; P=0.12). By gross appearance, mixed/heterogeneous clots had lower FPE rates than red and white clots.

CONCLUSIONS

Despite the lack of correlation between clot histology and FPE, our study adds to the growing evidence supporting the notion that clot composition influences recanalization treatment strategy outcomes.

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

BACKGROUND

Nowadays, there is no method to quantitatively characterize the material composition of acute ischemic stroke thrombi prior to intervention, but dual-energy CT (DE-CT) offers imaging-based multimaterial decomposition. We retrospectively investigated the material composition of thrombi ex vivo using DE-CT with histological analysis as a reference.

METHODS

Clots of 70 patients with acute ischemic stroke were extracted by mechanical thrombectomy and scanned ex vivo in formalin-filled tubes with DE-CT. Multimaterial decomposition in the three components, i.e., red blood cells (RBC), white blood cells (WBC), and fibrin/platelets (F/P), was performed and compared to histology (hematoxylin/eosin staining) as reference. Attenuation and effective Z values were assessed, and histological composition was compared to stroke etiology according to the Trial of ORG 10172 in Acute Stroke Treatment (TOAST) criteria.

RESULTS

Histological and imaging analysis showed the following correlation coefficients for RBC (r = 0.527, p < 0.001), WBC (r = 0.305, p = 0.020), and F/P (r = 0.525, p < 0.001). RBC-rich thrombi presented higher clot attenuation in Hounsfield units than F/P-rich thrombi (51 HU versus 42 HU, p < 0.01). In histological analysis, cardioembolic clots showed less RBC (40% versus 56%, p = 0.053) and more F/P (53% versus 36%, p = 0.024), similar to cryptogenic clots containing less RBC (34% versus 56%, p = 0.006) and more F/P (58% versus 36%, p = 0.003) than non-cardioembolic strokes. No difference was assessed for the mean WBC portions in all TOAST groups.

CONCLUSIONS

DE-CT has the potential to quantitatively characterize the material composition of ischemic stroke thrombi.

RELEVANCE STATEMENT

Using DE-CT, the composition of ischemic stroke thrombi can be determined. Knowledge of histological composition prior to intervention offers the opportunity to define personalized treatment strategies for each patient to accomplish faster recanalization and better clinical outcomes.

KEY POINTS

• Acute ischemic stroke clots present different recanalization success according to histological composition. • Currently, no method can determine clot composition prior to intervention. • DE-CT allows quantitative material decomposition of thrombi ex vivo in red blood cells, white blood cells, and fibrin/platelets. • Histological clot composition differs between stroke etiology. • Insights into the histological composition in situ offer personalized treatment strategies.

Clot-based time attenuation curve as a novel imaging predictor of mechanical thrombectomy functional outcome in acute ischemia stroke

OBJECTIVES

To investigate whether a novel assessment of thrombus permeability obtained from perfusion computed tomography (CTP) can act as a more accurate predictor of clinical response to mechanical thrombectomy (MT) in acute ischemic stroke (AIS).

MATERIALS AND METHODS

We performed a study including two cohorts of AIS patients who underwent MT admitted to a single-center between April 2018 and February 2022: a retrospective development cohort (n = 71) and a prospective independent validation cohort (n = 96). Thrombus permeability was determined in terms of entire thrombus time-attenuation curve (TAC) on CTP. Association between thrombus TAC distributions and histopathological results was analyzed in the development cohort. Logistic regression was used to assess the performance of the TAC for predicting 90-day modified Rankin Scale (mRS) score, and good outcome was defined as a mRS score of  ≤ 2. Basic clinical characteristics was used to build a routine clinical model. A combined model gathered TAC and basic clinical characteristics was also developed. The performance of the three models is compared on the independent validation set.

RESULTS

Two TAC distributions were observed-unimodal (uTAC) and linear (lTAC). TAC distributions achieved strong correlations (|r|= 0.627, p < 0.001) with histopathological results, in which uTAC associated with fibrin- and platelet-rich clot while lTAC associated with red blood cell-rich clot. The uTAC was independently associated with poor outcome (odds ratio, 0.08 [95% confidence interval (CI), 0.02-0.31]; p < 0.001). TAC distributions yielded an AUC of 0.78 (95% CI, 0.70-0.87) for predicting clinical outcome. When combined clinical characteristics, the performance was significantly improved (AUC, 0.85 [95% CI, 0.76-0.93]; p < 0.001) and higher than routine clinical model (AUC, 0.69 [95% CI, 0.59-0.83]; p < 0.001).

CONCLUSIONS

Thrombus TAC on CTP were found to be a promising new imaging biomarker to predict the outcomes of MT in AIS.

CLINICAL RELEVANCE STATEMENT

This study revealed that clot-based time attenuation curve based on admission perfusion CT could reflect the permeability and composition of thrombus and, also, provide valuable information to predict the clinical outcomes of mechanical thrombectomy in patients with acute ischemia stroke.

KEY POINTS

• Two time-attenuation curves distributions achieved strong correlations (|r|= 0.627, p < 0.001) with histopathological results. • The unimodal time-attenuation curve was independently associated with poor outcome (odds ratio, 0.08 [0.02-0.31]; p < 0.001). • The time-attenuation curve distributions yielded a higher performance for detecting clinical outcome than routine clinical model (AUC, 0.78 [0.70-0.87] vs 0.69 [0.59-0.83]; p < 0.001).

Dynamic Perviousness Predicts Revascularization Success in Acute Ischemic Stroke

BACKGROUND

The predictive value of thrombus perviousness in acute ischemic stroke (AIS), as measured by computed tomography (CT), has been intensively studied with conflicting results. In this study, we investigate the predictive potential of the novel concept of dynamic perviousness using three-dimensional (3D) volumetric evaluation of occlusive thrombi.

METHODS

The full thrombus volume in 65 patients with a hyperdense artery sign on non-contrast CT (NCCT), who underwent mechanical thrombectomy (MT), was segmented. Perviousness maps were computed voxel-wise for the entire thrombus volume as thrombus attenuation increase (TAI) between NCCT and CT angiography (CTA) as well as between CTA and late venous phase CT (CTV). Perviousness was analyzed for its association with NIHSS at admission, Thrombolysis In Cerebral Infarction (TICI) score, and number of MT passes.

RESULTS

The mean late-uptake TAI of thrombi with NIHSS scores greater than 21 at admission was approximately 100% higher than for lower scored NIHSS (p between 0.05 and 0.005). Concerning revascularization results, thrombi requiring less than four MT passes had ca. 80% higher group mean late-uptake TAI than clots requiring four or more passes (p = 0.03), and thrombi with TICI score III had ca. 95% higher group mean late-uptake TAI than thrombi with TICI II (p = 0.03). Standard perviousness showed no significant correlation with MT results.

CONCLUSION

Standard thrombus perviousness of 3D clot volume is not associated with revascularization results in AIS. In contrast, dynamic perviousness assessed with a voxel-wise characterization of 3D thrombi volume may be a better predictor of MT outcomes than standard perviousness.

A prospective, multicentre, registry study of RECO in the endovascular treatment of acute ischaemic stroke

The RECO is a novel endovascular treatment (EVT) device that adjusts the distance between two mesh segments to axially hold the thrombus. We organized this postmarket study to assess the safety and performance of RECO in acute ischaemic stroke (AIS) patients with large vessel occlusion (LVO). This was a single-arm prospective multicentre study that enrolled patients as first-line patients treated with RECO at 9 stroke centres. The primary outcome measures included functional independence at 90 days (mRS 0-2), symptomatic intracranial haemorrhage (sICH), time from puncture to recanalization and time from symptom onset to recanalization. The secondary outcome measures were a modified thrombolysis in cerebral infarction (mTICI) score of 2b or 3 after the first attempt and at the end of the procedure and the all-cause mortality rate within 90 days. From May 22, 2020, to July 30, 2022, a total of 268 consecutive patients were enrolled in the registry. The median puncture-to-recanalization time was 64 (IQR, 45-92), and the symptom onset-to-recanalization time was 328 min (IQR, 228-469). RECO achieved successful reperfusion (mTICI 2b-3) after the first pass in 133 of 268 patients (49.6%). At the end of the operation, 96.6% of the patients reached mTICI 2b-3, and 97.4% of the patients ultimately achieved successful reperfusion. Sixteen (7.2%) patients had sICH. A total of 132 (49.3%) patients achieved functional independence at 90 days, and the all-cause mortality rate within 90 days was 17.5%. In this clinical experience, the RECO device achieved a high rate of complete recanalization with a good safety profile and favourable 90-day clinical outcomes.Clinical trial registration: URL: https://www.clinicaltrials.gov/ ; Unique identifier: NCT04840719.

Quality assessment of histopathological stainings on prolonged formalin fixed thrombus tissues retrieved by mechanical thrombectomy

Background

Formalin-fixed retrieved clots from mechanical thrombectomy (MT) are now routinely studied using both conventional histopathologic techniques and immunohistochemistry (IHC). However, the effects of prolonged formalin fixation on the histological results of clot analysis remain unknown. The objective of this study was to investigate the effects of prolonged formalin fixation on quality of histopathologic stainings of thrombus tissues retrieved by MT.

Methods

As part of the multicenter EXCELLENT registry, a total of 80 clots extracted by MT from acute ischemic stroke patients were randomly selected from the tissue database and assigned into four groups according to 10% neutral buffered formalin (NBF) fixation duration (1-30, 30-60, 60-90, and 90+ days, up to 2 years). Samples underwent processing and sectioning. Two serial sections for each case were stained with hematoxylin and eosin (H&E), Martius Scarlet Blue (MSB), and IHC for CD42b (platelet marker). An expert pathologist, who was blinded to tissue fixation duration and patient clinical data, assessed the quality of each stain including stainability, sensitivity, specificity, and consistency of stainings.

Results

No significant issues were encountered during tissue processing and sectioning. On H&E stain, 97.5% (78/80) of slides showed good-quality staining, demonstrating clear histological properties of the thrombus tissue as red blood cells (RBC) stained in red, fibrin/platelet stained in pink, and nuclei stained in blue with intranuclear detail. The same histological features were also successfully demonstrated on MSB for all 80 samples. One of the 80 samples (1.2%) showed that RBC lost stainability on H&E due to tissue autolysis. Clear positive signal of platelet staining was expressed in 98.8% of the samples (79/80) with minimal background staining on IHC. There was no significant difference in staining quality across different formalin fixation groups.

Conclusion

A good quality of histopathological staining is achievable for the thrombus tissue fixed in 10% neutral buffered formalin for up to 2 years. The findings are limited to the thrombus tissue retrieved by MT and specific fixation and staining protocols used in the study. To apply these results to other tissue or experimental setups, further studies and validations would be necessary.

Clinical trial registration

This study was conducted as part of the EXCELLENT study: www.clinicaltrials.gov, unique identifier: NCT03685578.

Endovascular treatment of acute ischemic stroke in childhood: A comprehensive literature review based on the experience of a single center

Acute ischemic stroke (AIS) in childhood is a relatively rare but significant condition that can result in long-term disabilities. There is a lack of standardized strategies for diagnosing and treating pediatric AIS due to limited evidence-based data on thrombolytic and endovascular treatments in children. This comprehensive literature review focuses on the experience of a single center in Italy and aims to highlight the main peculiarities of endovascular treatment (EVT) for AIS in childhood. The review covers the diagnostic workup, the endovascular procedures, and the need for a specific thrombectomy program for pediatric AIS. The review discusses the indications and considerations for thrombectomy in children, including the risk of complications and the challenges of extrapolating results from adult studies. The diagnostic protocols for pediatric AIS are also discussed, emphasizing the use of MRI to avoid X-ray and contrast medium exposure in children. The combination of intravenous thrombolysis and mechanical thrombectomy has been examined, considering the differences between pediatric and adult thrombi. Technical considerations related to the size of pediatric patients are addressed, including the use of large bore catheters and potential concerns with access points. The organization of a thrombectomy program for pediatric AIS is discussed, emphasizing the need for specialized facilities and expertise. Although evidence for EVT in the pediatric population is based on case series, the importance of specialized centers and the lack of validated guidelines are evident.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Coagulation Factor Expression and Composition of Arterial Thrombi in Cancer-Associated Stroke

BACKGROUND

Cancer is associated with an increased risk of stroke. Tumor cells activate platelets, induce a coagulation cascade, and generate thrombin. The composition of thrombi may reflect the mechanism of thrombosis, aiding the determination of the treatment strategy. Here, we investigated the composition and expression of coagulation factors in the thrombi of patients with cancer-associated stroke.

METHODS

Patients with stroke who underwent endovascular thrombectomy between September 2014 and June 2020 and whose cerebral thrombi were obtained were divided into those with cancer-associated stroke (cancer group) and propensity score-matched patients without cancer (control group), using 1:1 matching based on age and sex. Immunohistochemistry was performed of the thrombi, and the composition and expression of coagulation factors were compared between groups.

RESULTS

Among the 320 patients who underwent endovascular thrombectomy and who had thrombi obtained, this study included 23 patients with cancer and 23 matched controls. In both groups, the median age was 65 years, and 12 patients (52.2%) were men. Platelet composition was significantly higher in the cancer group than in the control group (median [interquartile range], 51.3% [28.0%-61.4%] versus 9.5% [4.8%-14.0%]; P<0.001). Among coagulation factors, thrombin (26.2% [16.2%-52.7%] versus 4.5% [1.3%-7.2%]; P<0.001) and tissue factors (0.60% [0.34%-2.06%] versus 0.37% [0.22%-0.60%]; P=0.024) were higher and factor X was lower (1.25% [0.39%-3.60%] versus 2.33% [1.67%-4.48%]; P=0.034) in the cancer group. There was a positive correlation between thrombin and platelets in the cancer group (r=0.666; P=0.001) but not in the control group (r=-0.167; P=0.627).

CONCLUSIONS

Cerebral thrombi in patients with cancer-associated stroke showed higher proportions of platelets, thrombin, and tissue factors, suggesting their key roles in arterial thrombosis in cancer and providing a therapeutic perspective for preventing stroke in patients with cancer-associated stroke.

Susceptibility vessel sign, a predictor of long-term outcome in patients with stroke treated with mechanical thrombectomy

BACKGROUND

The absence of the susceptibility vessel sign (SVS) in patients treated with mechanical thrombectomy (MT) is associated with poor radiological and clinical outcomes after 3 months. Underlying conditions, such as cancer, are assumed to influence SVS status and could potentially impact the long-term outcome. We aimed to assess SVS status as an independent predictor of long-term outcomes in MT-treated patients.

METHODS

SVS status was retrospectively determined in consecutive MT-treated patients at a comprehensive stroke center between 2010 and 2018. Predictors of long-term mortality and poor functional outcome (modified Rankin Scale (mRS) ≥3) up to 8 years were identified using multivariable Cox and logistic regression, respectively.

RESULTS

Of the 558 patients included, SVS was absent in 13% (n=71) and present in 87% (n=487) on baseline imaging. Patients without SVS were more likely to have active cancer (P=0.003) and diabetes mellitus (P<0.001) at the time of stroke. The median long-term follow-up time was 1058 days (IQR 533-1671 days). After adjustment for active cancer and diabetes mellitus, among others, the absence of SVS was associated with long-term mortality (adjusted HR (aHR) 2.11, 95% CI 1.35 to 3.29) and poor functional outcome in the long term (adjusted OR (aOR) 2.90, 95% CI 1.29 to 6.55).

CONCLUSION

MT-treated patients without SVS have higher long-term mortality rates and poorer long-term functional outcome. It appears that this association cannot be explained by comorbidities alone, and further studies are warranted.

Management and Prognosis of Acute Stroke in Atrial Fibrillation

Atrial fibrillation (AF) is an important risk factor for ischemic stroke (IS). Oral anticoagulation (OAC) significantly reduces the risk of IS in AF but also increases the risk of systemic bleeding, including intracerebral hemorrhage (ICH). AF-related strokes are associated with greater disability and mortality compared to non-AF strokes. The management of patients with AF-related strokes is challenging, and it involves weighing individual risks and benefits in the acute treatment and preventive strategies of these patients. This review summarizes the current knowledge of the acute management of ischemic and hemorrhagic stroke in patients with AF, and the prognosis and potential implications for management both in the acute and long-term setting.

Imaging features of cardioembolic stroke on 4-dimensional computed tomography angiography

Background

Identifying cardioembolic stroke is important for the decision-making of endovascular treatment and anticoagulation therapy. We aimed to explore the features of cardioembolic stroke on 4-dimensional (4D) computed tomography angiography (4D-CTA) and assess whether these features can assist in classifying stroke etiology.

Methods

In this retrospective study, we analyzed the images of 294 patients with acute ischemic stroke (AIS) from July 2020 to February 2022 at the First Affiliated Hospital of Chongqing Medical University, which had been consecutively collected. The data of 110 patients with occlusion of the M1/M2 segment of the middle cerebral artery (MCA) with/without intracranial internal carotid artery (ICA) occlusion were analyzed to calculate the clot burden score (CBS) and collateral score (CS), and the data of 88 patients with a clear origin and distal part were analyzed to measure clot length. Maximum intensity projection (MIP) and time MIP (tMIP) post-processing were used to assess the clot features. The Mann-Whitney U test was used to compare the clot characteristics between the 2 groups. Binary logistic regression was performed to assess the association between the image characteristics and cardioembolic stroke. Moreover, the receiver operating characteristic (ROC) curve was used to test the diagnostic efficacy of MIP/tMIP clot features in classifying cardioembolic stroke.

Results

Age, high-risk factors for cerebrovascular disease, high/medium-risk sources of cardioembolic stroke, clot length, CBS, and CS were significantly different between the cardioembolic stroke group and non-cardioembolic stroke group (P<0.05). In the cardioembolic stroke group, the median MIP and tMIP clot length was 12 mm [interquartile range (IQR), 8.3-17.4 mm] and 9.3 mm (IQR, 6.8-14.3 mm), respectively. In the non-cardioembolic stroke group, the median MIP and tMIP clot length was 6.5 mm (IQR, 4.7-11.5 mm) and 5.8 mm (IQR, 3.9-10.6 mm), respectively. Binary logistic regression showed that cardioembolic stroke was significantly associated with MIP-clot length [odds ratio (OR), 1.15; 95% confidence interval (CI): 1.02-1.29; P<0.05], tMIP-clot length (OR, 1.18; 95% CI: 1.02-1.36; P<0.05), and tMIP-CBS (OR, 3.96; 95% CI: 1.08-14.58; P<0.05). The area under the ROC curve (AUC) values of MIP clot length for identifying cardioembolic stroke were 0.75 (95% CI: 0.65-0.84, P<0.05), with a cut-off value of >7.4 mm [sensitivity: 84.62% (95% CI: 69.50-94.10%); specificity: 59.18% (95% CI: 44.20-73.00%)]. The AUC value of tMIP clot length was 0.72 (95% CI: 0.61-0.81, P<0.05), with a cut-off value of >5.4 mm [sensitivity: 92.31% (95% CI: 79.10-98.40%); specificity: 48.98% (95% CI: 34.40-63.70%)].

Conclusions

Clot length and CBS were overestimated on MIP images. Among the clot characteristics, clot length could identify cardioembolic stroke.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Gene expression profiles of ischemic stroke clots retrieved by mechanical thrombectomy are associated with disease etiology

BACKGROUND

Determining stroke etiology is crucial for secondary prevention, but intensive workups fail to classify ~30% of strokes that are cryptogenic.

OBJECTIVE

To examine the hypothesis that the transcriptomic profiles of clots retrieved during mechanical thrombectomy are unique to strokes of different subtypes.

METHODS

We isolated RNA from the clots of 73 patients undergoing mechanical thrombectomy. Samples of sufficient quality were subjected to 100-cycle, paired-end RNAseq, and transcriptomes with less than 10 million unique reads were excluded from analysis. Significant differentially expressed genes (DEGs) between subtypes (defined by the Trial of Org 10 172 in Acute Stroke Treatment) were identified by expression analysis in edgeR. Gene ontology enrichment analysis was used to study the biologic differences between stroke etiologies.

RESULTS

In all, 38 clot transcriptomes were analyzed; 6 from large artery atherosclerosis (LAA), 21 from cardioembolism (CE), 5 from strokes of other determined origin, and 6 from cryptogenic strokes. Among all comparisons, there were 816 unique DEGs, 174 of which were shared by at least two comparisons, and 20 of which were shared by all three. Gene ontology analysis showed that CE clots reflected high levels of inflammation, LAA clots had greater oxidoreduction and T-cell processes, and clots of other determined origin were enriched for aberrant platelet and hemoglobin-related processes. Principal component analysis indicated separation between these subtypes and showed cryptogenic samples clustered among several different groups.

CONCLUSIONS

Expression profiles of stroke clots were identified between stroke etiologies and reflected different biologic responses. Cryptogenic thrombi may be related to multiple etiologies.

Thrombus imaging characteristics within acute ischemic stroke: similarities and interdependence

BACKGROUND

The effects of thrombus imaging characteristics on procedural and clinical outcomes after ischemic stroke are increasingly being studied. These thrombus characteristics - for eg, size, location, and density - are commonly analyzed as separate entities. However, it is known that some of these thrombus characteristics are strongly related. Multicollinearity can lead to unreliable prediction models. We aimed to determine the distribution, correlation and clustering of thrombus imaging characteristics based on a large dataset of anterior-circulation acute ischemic stroke patients.

METHODS

We measured thrombus imaging characteristics in the MR CLEAN Registry dataset, which included occlusion location, distance from the intracranial carotid artery to the thrombus (DT), thrombus length, density, perviousness, and clot burden score (CBS). We assessed intercorrelations with Spearman's coefficient (ρ) and grouped thrombi based on 1) occlusion location and 2) thrombus length, density and perviousness using unsupervised clustering.

RESULTS

We included 934 patients, of which 22% had an internal carotid artery (ICA) occlusion, 61% M1, 16% M2, and 1% another occlusion location. All thrombus characteristics were significantly correlated. Higher CBS was strongly correlated with longer DT (ρ=0.67, p<0.01), and moderately correlated with shorter thrombus length (ρ=-0.41, p<0.01). In more proximal occlusion locations, thrombi were significantly longer, denser, and less pervious. Unsupervised clustering analysis resulted in four thrombus groups; however, the cohesion within and distinction between the groups were weak.

CONCLUSIONS

Thrombus imaging characteristics are significantly intercorrelated - strong correlations should be considered in future predictive modeling studies. Clustering analysis showed there are no distinct thrombus archetypes - novel treatments should consider this thrombus variability.

Factors related to white thrombi in acute ischemic stroke in cancer patients

OBJECTIVES

Thrombi in cerebral large vessel occlusion associated with active cancer are often fibrin and platelet-rich white thrombi. However, evaluating the thrombus composition in a short time before thrombectomy is often ineffective. We sought to determine factors related to white thrombi in acute ischemic stroke due to large vessel occlusion in cancer patients.

METHODS

Consecutive cancer patients undergoing thrombectomy for acute ischemic stroke due to large vessel occlusion between January 2018 and May 2022 were retrospectively reviewed. The patients were classified into white thrombus and red thrombus groups on the basis of the pathological findings of retrieved thrombi. Patient characteristics and laboratory findings were compared between the two groups.

RESULTS

There were 12 patients in the white thrombus group and 11 patients in the red thrombus group. Active cancer was significantly more in the white thrombus group than in the red thrombus group (91.7% vs. 36.3%, p = 0.0094). Internal carotid artery occlusion was significantly less in the white thrombus group than in the red thrombus group (0% vs. 36.4%, p = 0.037). Among laboratory findings, D-dimer levels were an independent factor associated with white thrombi (odds ratio 8.97 [95% confidence interval 1.71-368.99], p < 0.0001). The cutoff value of D-dimer levels for predicting white thrombi was 3.5 μg/mL (83.3% sensitivity and 100% specificity).

CONCLUSIONS

In acute ischemic stroke in cancer patients, active cancer, no internal carotid artery occlusion, and higher D-dimer levels (≥3.5 μg/mL) may be associated with occlusion with fibrin and platelet-rich white thrombi.

Pleocytosis in cerebrospinal fluid attributed to ischemic stroke: A review of the literature

INTRODUCTION

Lumbar puncture is generally performed in stroke settings when infectious or inflammatory diseases are suspected to be the etiology. This review aimed to assess the prevalence of pleocytosis in the cerebrospinal fluid following ischemic stroke without inflammatory or infectious etiology.

METHODS

We searched PubMed for studies with mentions of "[ischemic stroke] AND [cerebrospinal fluid]". We included only studies written in English, including patients with a primary diagnosis of either ischemic stroke or transient ischemic attack (TIA), and where white blood cell count in the spinal fluid was presented. Studies investigating common etiologies for pleocytosis, was excluded. Study and patient characteristics, white blood cell count and time to lumbar puncture were presented in tables, and the prevalence of pleocytosis were reported and plotted graphically.

RESULTS

We included 15 studies with 1607 patients, 1522 with ischemic stroke and 85 with TIA. The prevalence of pleocytosis was between 0% to 28,6% and a mean of 11.8%. The highest white blood cell count found with common etiologies for pleocytosis ruled out was 56 cells/mm3. A mean white blood cell count of 4.0 was based on the three studies where this was available.

DISCUSSION

The included studies were methodologically heterogenous and few had pleocytosis as primary outcome. Pleocytosis following ischemic stroke is uncommon and should prompt further investigations.

Comparing CT and MR Properties of Artificial Thrombi According to Their Composition

This study aims to determine whether and to what extent the structure and composition of thrombi can be assessed using NMR and CT measurements. Seven different thrombus models, namely, six RBC thrombi with hematocrit levels (HTs) of 0%, 20%, 40%, 60%, 80% and 100% and one platelet thrombus model, were analyzed using proton NMR at 100 MHz and 400 MHz, with measurements of T₁ and T₂ NMR relaxation times and measurements of the apparent diffusion coefficient (ADC). In addition, the thrombus models were CT-scanned in a dual-energy mode (80 kV and 140 kV) and in a single-energy mode (80 kV) to measure their CT numbers. The results confirmed that RBC thrombi can be distinguished from platelet thrombi by using ADC and CT number measurements in all three settings, while they cannot be distinguished by using T₁ and T₂ measurements. All measured parameters allowed for the differentiation of RBC thrombi according to their HT values, but the best sensitivity to HT was obtained with ADC and single-energy CT measurements. The importance of this study also lies in the potential application of its results for the characterization of actual thrombi in vivo.

Identifying ex vivo acute ischemic stroke thrombus composition using electrochemical impedance spectroscopy

BACKGROUND

Intra-procedural characterization of stroke thromboemboli might guide mechanical thrombectomy (MT) device choice to improve recanalization rates. Electrochemical impedance spectroscopy (EIS) has been used to characterize various biological tissues in real time but has not been used in thrombus.

OBJECTIVE

To perform a feasibility study of EIS analysis of thrombi retrieved by MT to evaluate: (1) the ability of EIS and machine learning to predict red blood cell (RBC) percentage content of thrombi and (2) to classify the thrombi as "RBC-rich" or "RBC-poor" based on a range of cutoff values of RBC.

METHODS

ClotbasePilot was a multicentric, international, prospective feasibility study. Retrieved thrombi underwent histological analysis to identify proportions of RBC and other components. EIS results were analyzed with machine learning. Linear regression was used to evaluate the correlation between the histology and EIS. Sensitivity and specificity of the model to classify the thrombus as RBC-rich or RBC-poor were also evaluated.

RESULTS

Among 514 MT,179 thrombi were included for EIS and histological analysis. The mean composition in RBC of the thrombi was 36% ± 24. Good correlation between the impedance-based prediction and histology was achieved (slope of 0.9, R²  =  0.53, Pearson coefficient  =  0.72). Depending on the chosen cutoff, ranging from 20 to 60% of RBC, the calculated sensitivity for classification of thrombi ranged from 77 to 85% and the specificity from 72 to 88%.

CONCLUSION

Combination of EIS and machine learning can reliably predict the RBC composition of retrieved ex vivo AIS thrombi and then classify them into groups according to their RBC composition with good sensitivity and specificity.

Effect of Truncal-Type Occlusion Based on Multiphase or Single-Phase Computed Tomographic Angiography in Predicting Intracranial Atherosclerotic Stenosis-Related Acute Middle Cerebral Artery Occlusion

OBJECTIVE

To investigate whether truncal-type occlusion based on multiphase computed tomographic angiography (mpCTA) was more effective for predicting intracranial atherosclerotic stenosis-related occlusion (ICAS-O) than occlusion type based on single-phase computed tomographic angiography (spCTA) in patients with acute ischemic stroke with large-vessel occlusion (AIS-LVO) in the middle cerebral artery (MCA).

METHODS

Data were retrospectively collected from 72 patients with AIS-LVO in the MCA between January 2018 and December 2019. The occlusion types included truncal-type and branching-site occlusions. The association between ICAS-O and occlusion type based on the 2 computed tomographic angiography patterns was analyzed, and receiver operating characteristic curves were plotted for assessment. The areas under the curve were compared to determine the difference between the predictive powers of truncal-type occlusion based on mpCTA and spCTA.

RESULTS

Among the 72 patients, 16 were classified as having ICAS-O and 56 as having embolisms. In univariate analysis, truncal-type occlusion was significantly associated with ICAS-O (P < 0.001 for mpCTA and P = 0.001 for spCTA). After multivariable analysis, truncal-type occlusion based on both mpCTA and spCTA remained independently associated with ICAS-O (P = 0.002 for mpCTA and P = 0.029 for spCTA). The areas under the curve were 0.821 for mpCTA and 0.683 for spCTA; this difference was statistically significant (P = 0.024).

CONCLUSIONS

In patients with AIS-LVO in the MCA, truncal-type occlusion based on mpCTA enables more accurate detection of ICAS-O than that based on spCTA.

Advancing Stroke Research on Cerebral Thrombi with Omic Technologies

Cerebrovascular diseases represent a leading cause of disability, morbidity, and death worldwide. In the last decade, the advances in endovascular procedures have not only improved acute ischemic stroke care but also conceded a thorough analysis of patients' thrombi. Although early anatomopathological and immunohistochemical analyses have provided valuable insights into thrombus composition and its correlation with radiological features, response to reperfusion therapies, and stroke etiology, these results have been inconclusive so far. Recent studies applied single- or multi-omic approaches-such as proteomics, metabolomics, transcriptomics, or a combination of these-to investigate clot composition and stroke mechanisms, showing high predictive power. Particularly, one pilot studies showed that combined deep phenotyping of stroke thrombi may be superior to classic clinical predictors in defining stroke mechanisms. Small sample sizes, varying methodologies, and lack of adjustments for potential confounders still represent roadblocks to generalizing these findings. However, these techniques hold the potential to better investigate stroke-related thrombogenesis and select secondary prevention strategies, and to prompt the discovery of novel biomarkers and therapeutic targets. In this review, we summarize the most recent findings, overview current strengths and limitations, and present future perspectives in the field.

Reverse Translation to Develop Post-stroke Therapeutic Interventions during Mechanical Thrombectomy: Lessons from the BACTRAC Trial

The majority of strokes, approximately 87%, are ischemic in etiology with the remaining hemorrhagic in origin. Emergent large vessel occlusions (ELVOs) are a subtype of ischemic stroke accounting for approximately 30-40% of acute large vessel blockages. Treatment for ELVOs focuses on recanalization of the occluded vessel by time-sensitive administration of tissue plasminogen activator (tPA) or thrombus removal using mechanical thrombectomy. Although a great deal of time and resources have focused on translational stroke research, little progress has been made in the area of identifying additional new treatments for stroke. Translational limitations include difficulty simulating human comorbid conditions in animal models, as well as the temporal nature of stroke pathology. The Blood And Clot Thrombectomy Registry And Collaboration represents an ongoing tissue registry for thrombectomy patients and includes collection of intracranial arterial blood, systemic arterial blood, thrombi, as well as a series of clinical and radiographic data points for analysis. This chapter will explore the methodologies employed and results obtained from studying BACTRAC-derived human biological specimens and how they can inform translational experimental design in animal studies.

Computational analysis of effects of clot length on Acute ischemic stroke recanalization under different cyclic aspiration loading conditions

Acute ischemic stroke, the second leading cause of death worldwide, results from occlusion of a cerebral artery by a blood clot. Application of cyclic aspiration using an aspiration catheter is a current therapy for the removal of lodged clots. In this study, we perform finite element simulations to analyze deformation of long clots, having length to radius ratio of 2-10, which corresponds to clot-length of 2.85-14.25 mm, under peak-to-peak cyclic aspiration pressures of 10-50 mmHg, and frequencies of 0.5, 1, and 2 Hz. Our computational system comprises of a nonlinear viscoelastic solid clot, a hyperelastic artery, and a nonlinear viscoelastic cohesive zone, the latter modeling the clot-artery interface. We observe that clots having length-to-radius ratio approximately greater than two separate from the inner arterial surface somewhere between the axial and distal ends, irrespective of the cyclic aspiration loading conditions. The stress distribution within the clot shows large tensile stresses in the clot interior, indicating the possibility of simultaneous fragmentation of the clot. Thus, this study shows us the various failure mechanisms simultaneously present in the clot during cyclic aspiration. Similarly, the stress distribution within the artery implies a possibility of endothelial damage to the arterial wall near the end where the aspiration pressure is applied. This framework provides a foundation for further investigation to clot fracture and adhesion characterization.

Hyperdense middle cerebral artery sign predicts favorable outcome in patients undergoing mechanical thrombectomy

Non-contrast computer tomography detects the presence of hyperdense middle cerebral artery sign (HMCAS). Studies on the prognostic value of HMCAS among patients undergoing mechanical thrombectomy (MT) are conflicting. A retrospective analysis of consecutive patients with acute ischemic stroke due to middle cerebral artery occlusion, presenting with or without HMCAS, who underwent MT, was performed. We enrolled 191 patients (HMCAS +, n = 140; HMCAS -, n = 51). Prevalence of successful recanalization was significantly higher in patients with HMCAS than in those without HMCAS (92.1% versus 74.5%, p = 0.001). Patients with HMCAS had a better clinical outcome than those HMCAS - (54.3% versus 37.3%, p = 0.037, for three-month favorable outcome; 62.9% versus 39.3%, p = 0.004, for major neurological improvement at discharge; 8.6% versus 19.6%, p = 0.035, for in-hospital mortality; 14.3% versus 27.5%, p = 0.035, for intracranial hemorrhage; 2.9% versus 17.6%, p = 0.001, for symptomatic intracranial hemorrhage). Multivariate analyses confirmed that HMCAS represents an independent predictor of three-month favorable outcome (OR 2.48, 95% CI 1.10-5.58, p = 0.028), major neurological improvement at discharge (OR 2.40, 95% CI 1.09-5.20, p = 0.030), in-hospital mortality (OR 0.29, 95% CI 0.010-0.81, p = 0.018), presence of ICH (OR 0.49, 95% CI 0.25-0.97, p = 0.042) and presence of SICH (OR 0.16, 95% CI 0.04-0.63, p = 0.009). HMCAS presence predicts favorable outcome in patients undergoing MT. This result may indicate that hyperdense clots are more likely to respond to MT than isodense ones. This effect is mediated by reduction in hemorrhagic transformation.

A nomogram for predicting thrombus composition in stroke patients with large vessel occlusion: combination of thrombus density and perviousness with clinical features

PURPOSE

To establish a nomogram incorporating pretreatment imaging parameters and clinical characteristics for predicting the thrombus composition of acute ischemic stroke (AIS) with large vessel occlusion (LVO).

METHODS

We retrospectively enrolled patients with occlusion of the Middle Cerebral Artery (MCA) who underwent Mechanical Thrombectomy (MT). Retrieved thrombi were stained with Hematoxylin and Eosin (H&E) and Martius Scarlet Blue (MSB). Thrombi are assigned to the Fibrin-rich or RBC-rich group based on the relative fractions of Red Blood Cells (RBC), fibrin, and platelet. The independent risk factors for Fibrin-rich clots were determined via univariate and multivariate logistic regression analysis and were then integrated to establish a nomogram.

RESULTS

In total, 98 patients were included in this study. Patients with fibrin-rich clots had worse functional outcome [modified Rankin scale (mRS) 0-2, 34.7% vs 63.2%, p = 0.005], longer procedure time (76.8 min vs 50.8 min, p = 0.001), and increased maneuvers of MT (1.84 vs 1.46, p = 0.703) than those with RBC-rich clots. The independent risk factors for Fibrin-rich clots were lower perviousness measured by Non-Contrast Computer Tomography (NCCT) and CT Angiography (CTA), lower thrombus relative attenuation on NCCT, elevated Platelet-WBC ratio (PWR) of admission peripheral blood, and previous antithrombotic medication. The nomogram showed good discrimination with an area under the Receiver Operating Characteristic (ROC) curve (AUC) of 0.852 (95% CI: 0.778-0.926). The calibration curve and decision curve analysis also displayed satisfactory accuracy and clinical utility.

CONCLUSION

This study has developed and internally validated an easy-to-use nomogram which can help predict clot composition and optimize therapeutic strategies for thrombectomy.

Spatial heterogeneity of occlusive thrombus in acute ischemic stroke: A systematic review

Following the advent of mechanical thrombectomy, occlusive clots in ischemic stroke have been amply characterized using conventional histopathology. Many studies have investigated the compositional variability of thrombi and the consequences of thrombus composition on treatment response. More recent evidence has emerged about the spatial heterogeneity of the clot or the preferential distribution of its components and compact nature. Here we review this emerging body of evidence, discuss its potential clinical implications, and propose the development of adequate characterization techniques.

Prognostic value of radiomics-based hyperdense middle cerebral artery sign for patients with acute ischemic stroke after thrombectomy strategy

Background and purpose

The purpose of this study was to evaluate the prognostic value of radiomics-based hyperdense middle cerebral artery sign (HMCAS) for patients with acute ischemic stroke (AIS) after mechanical thrombectomy (MT) and to establish prediction models to identify patients who may benefit more from MT.

Methods

In this retrospective study, a total of 102 consecutive patients who presented with HMCAS on non-contrast computed tomography (NCCT) at admission and underwent MT in our hospital between January 2019 and December 2020 were recruited. Among them, 46 experienced favorable outcomes (modified Rankin Scale [mRS] ≤ 2) at 3 months of follow-up. All patients were categorized into two sets, namely, the training set (n = 81) and the test set (n = 21). Radiomics features (RFs) and clinical features (CFs) in the training set were selected by statistical analysis to create models. The models' discriminative ability was quantified using the area under the curve (AUC) and confirmed by decision curve analyses.

Results

The prediction model established using CFs before MT includes baseline National Institutes of Health Stroke Scale (NIHSS) and neutrophil-to-lymphocyte ratio (NLR) [AUC [95% confidence interval (CI)] = 0.596 (0.312-0.881)]. A total of 1,389 RFs were extracted from each hyperdense territory and 8 RFs were left to build the radiomics model [RM; AUC (95%CI) = 0.798 (0.598-0.998)]. The model using preoperative CFs and RFs showed good performance [AUC (95%CI) = 0.817 (0.625-1.000)]. The models using post-operative CFs alone [AUC (95%CI) = 0.856 (0.685-1.000)] or post-operative CFs with RFs [AUC (95%CI) = 0.894 (0.757-1.000)] also showed good discrimination.

Conclusion

The radiomics-based HMCAS might be a promising tool to predict the prognoses of patients with AIS after MT.

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

Background and aim

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

Methods

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

Results

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

Conclusion

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

Neuroimaging of Acute Ischemic Stroke: Multimodal Imaging Approach for Acute Endovascular Therapy

Advances in acute ischemic stroke (AIS) treatment have been contingent on innovations in neuroimaging. Neuroimaging plays a pivotal role in the diagnosis and prognosis of ischemic stroke and large vessel occlusion, enabling triage decisions in the emergent care of the stroke patient. Current imaging protocols for acute stroke are dependent on the available resources and clinicians' preferences and experiences. In addition, differential application of neuroimaging in medical decision-making, and the rapidly growing evidence to support varying paradigms have outpaced guideline-based recommendations for selecting patients to receive intravenous or endovascular treatment. In this review, we aimed to discuss the various imaging modalities and approaches used in the diagnosis and treatment of AIS.

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

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

Updates in mechanical thrombectomy

Stroke is a leading cause of morbidity and mortality. The advent of mechanical thrombectomy has largely improved patient outcomes. This article reviews the features and outcomes associated with aspiration, stent retrievers, and combination catheters used in current practice. There is also a discussion on clinical considerations based on anatomical features and clot composition. The reperfusion grading scale and outcome metrics commonly used following thrombectomy when a patient is still in the hospital are reviewed. Lastly, there are proposed discharge and outpatient follow-up goals in caring for patients hospitalized for a stroke.

Correlation of Neutrophil to Lymphocyte Ratio with Expression of Neutrophil Extracellular Traps Within Stroke Emboli

BACKGROUND & PURPOSE

It has been hypothesized that circulating neutrophils have a direct correlation with the composition of emboli in acute ischemic stroke (AIS). The aim of this study is to evaluate the association between neutrophil-lymphocyte ratio (NLR) in peripheral blood and the expression of neutrophil extracellular traps (NETs) within stroke emboli.

METHODS

Consecutive patients with acute ischemic stroke (AIS) due to large vessel occlusion (LVO) that underwent mechanical thrombectomy (MT) were included. Patients were divided into two groups based on NLR median value. Retrieved thrombi were histologically analyzed using Martius Scarlett Blue (MSB) for main thrombus components including red blood cells (RBCs), white blood cells (WBCs), fibrin and platelet. Immunohistochemistry staining for von Willebrand Factor (vWF) and anti-citrullinated H3 (H3Cit; NETs marker) was also performed.

RESULTS

Samples from a total of 84 patients were included. The average percentage of RBCs, WBCs, fibrin, platelet, H3Cit, and vWF components in thrombi were 45.1%, 3.5%, 21.8%, 29.6%, 19.7% and 14.8% respectively. When stratifying by NLR group [low (≤3.94) versus high (>3.95)], high NLR group had significantly more WBCs (4.5%), fibrin (24.2%), H3Cit (22.7%) and vWF (17.1%) thrombus fractions compared to low NLR group. Additionally, RBC content (38.8%) was lower in the high NLR group.

CONCLUSIONS

NLR is correlated with the amounts of WBCs, fibrin, NETs and vWF within the thrombi retrieved from AIS patients due to LVO.

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.

Magnetic resonance imaging quantitative T2* mapping to predict the red blood cell content of in vivo thrombi retrieved from patients with large vessel occlusions in acute ischemic stroke

BACKGROUND AND PURPOSE

Magnetic resonance imaging quantitative T2* mapping has shown reliable identification of thrombus red blood cell content in vitro. The thrombus composition has been in vivo, associated with outcomes after endovascular therapy for acute ischemic stroke. We aim to analyze the red blood cell content of thrombi retrieved from patients with large vessel occlusions in relation to the thrombus-T2* relaxation time in magnetic resonance imaging.

MATERIAL AND METHODS

Consecutive acute ischemic stroke patients treated by endovascular therapy were scanned with an magnetic resonance imaging quantitative T2* mapping sequence. Quantitative histologic evaluations of red blood cell content were performed. A linear regression assessed the association between vascular risk factors, comorbidities, antithrombotic drugs intake, baseline National Institutes of Health Stroke Scale (NIHSS), intravenous thrombolysis before endovascular therapy, time between onset and groin puncture, patient's outcome at 3 months, magnetic resonance imaging quantitative T2* mapping results, and the red blood cell content of thrombi. The correlation between the mean thrombus-T2* relaxation time and red blood cell content was assessed by calculating the Pearson correlation coefficient.

RESULTS

Among 31 thrombi, 16 were "Fibrin rich" and 15 "red blood cell dominant." The median red blood cell content was 39 (range, 0-90; interquartile range, 37). The median (interquartile range) thrombus-T2* relaxation time was shorter in "red blood cell dominant" thrombi (21, interquartile range 6) than in "Fibrin rich" thrombi (24, interquartile range 7), without significant difference (p = 0.15), as shown in the Box plot. An inverse correlation between thrombus-T2* relaxation time and red blood cell content was found, with a correlation coefficient of -0.41 (95% CI, -0.67 to -0.08, p = 0.02).

CONCLUSION

Our study shows that a shorter thrombus-T2* relaxation time is related to a higher red blood cell content within in vivo thrombi.

Novel synthetic clot analogs for in-vitro stroke modelling

Purpose

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

Methods

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

Results

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

Conclusion

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