The administration of rtPA before mechanical thrombectomy in acute ischemic stroke patients is associated with a significant reduction of the retrieved clot area but it does not influence revascularization outcome

Clinical significance and prevalence of subarachnoid hyperdensities on flat detector CT after mechanical thrombectomy: does it really matter?

BACKGROUND

Subarachnoid hyperdensities after mechanical thrombectomy (MT) are a common finding. However, it is often regarded as clinically insignificant.

OBJECTIVE

With this single-center investigation, to identify the prevalence of subarachnoid hyperdensities following MT, associated predictors, and the impact on the clinical outcome of the patients.

METHODS

383 patients from the stroke registry were analyzed for the presence of subarachnoid hyperdensities on flat detector CT (FDCT) directly after the completion of MT, and on follow-up dual-energy CT, then classified according to a visual grading scale. 178 patients were included with anterior circulation occlusions. Regression analysis was performed to identify significant predictors, and Kruskal-Wallis analysis and Χ2 test were performed to test the variables among the different groups. The primary outcome was the modified Rankin Scale (mRS) score at 90 days and was analyzed with the Wilcoxon-Mann-Whitney rank-sum test.

RESULTS

The prevalence of subarachnoid hyperdensities on FDCT was (66/178, 37.1%) with patients experiencing a significant unfavorable outcome (P=0.035). Significantly fewer patients with subarachnoid hyperdensities achieved a mRS score of ≤3 at 90 days 25/66 (37.9%) vs 60/112 (53.6%), P=0.043). In addition, mortality was significantly higher in the subarachnoid hyperdensities group (34.8% vs 19.6%, P=0.024). Distal occlusions and a higher number of device passes were significantly associated with subarachnoid hyperdensities (P=0.026) and (P=0.001), respectively. Patients who received intravenous tissue plasminogen activator had significantly fewer subarachnoid hyperdensities (P=0.029).

CONCLUSIONS

Postinterventional subarachnoid hyperdensities are a frequent finding after MT and are associated with neurological decline and worse functional outcome. They are more common with distal occlusions and multiple device passes.

Pharmacological preclinical comparison of tenecteplase and alteplase for the treatment of acute stroke

Alteplase (rtPA) remains the standard thrombolytic drug for acute ischemic stroke. However, new rtPA-derived molecules, such as tenecteplase (TNK), with prolonged half-lives following a single bolus administration, have been developed. Although TNK is currently under clinical evaluation, the limited preclinical data highlight the need for additional studies to elucidate its benefits. The toxicities of rtPA and TNK were evaluated in endothelial cells, astrocytes, and neuronal cells. In addition, their in vivo efficacy was independently assessed at two research centers using an ischemic thromboembolic mouse model. Both therapies were tested via early (20 and 30 min) and late administration (4 and 4.5 h) after stroke. rtPA, but not TNK, caused cell death only in neuronal cultures. Mice were less sensitive to thrombolytic therapies than humans, requiring doses 10-fold higher than the established clinical dose. A single bolus dose of 2.5 mg/kg TNK led to an infarct reduction similar to perfusion with 10 mg/kg of rtPA. Early administration of TNK decreased the hemorrhagic transformations compared to that by the early administration of rtPA; however, this result was not obtained following late administration. These two independent preclinical studies support the use of TNK as a promising reperfusion alternative to rtPA.

Development of physiologically relevant synthetic thrombus for use in visual analysis of in vitro mechanical thrombectomy device testing

BACKGROUND

Ischemic stroke is a leading cause of death and significant long-term disability worldwide. Mechanical thrombectomy is emerging as a standard treatment for eligible patients. As clinical implementation of stent retrieval and aspiration thrombectomy increases, there is a need for physiologically relevant in vitro device efficacy testing. Critical to this testing is the development of standardized 'soft' and 'hard' synthetic blood clots that mimic the properties of human thrombi and are compatible with imaging technologies. Synthetic clots allow researchers to extract information regarding clot integration, model hemodynamics, and quantify the physics of thrombectomy.

METHODS

This work develops polyacrylamide and alginate-based synthetic clots that are compatible with particle image velocimetry (PIV) and radiographic imaging techniques while maintaining mechanical properties of 'soft' and 'hard' human clots. Dynamic mechanical analysis testing using an HR2-Rheometer demonstrates comparable mechanical properties to human clots previously tested by this research group and provided in existing literature.

RESULTS

The synthetic clots are formulated with either 0.5% w/v polyethylene microspheres for PIV visualization or 20% w/v barium sulfate for angiographic visualization, enabling real-time imaging of clot behavior during thrombectomy simulations. The soft formulation shows compressive and shear properties of ~12 kPa and 2-3 kPa, respectively. The hard clots are 3-4 times stiffer, with compressive and shear properties of 41-42 kPa and 8-9 kPa, respectively.

CONCLUSION

Standardized synthetic clots offer a platform for reproducible device testing. This provides a greater understanding of mechanical thrombectomy device efficacy, which may lead to quantifiable advances in device development and eventual improved clinical outcomes.

iSPAN: Explainable prediction of outcomes post thrombectomy with Machine Learning

PURPOSE

This study aimed to develop and evaluate a machine learning model and a novel clinical score for predicting outcomes in stroke patients undergoing endovascular thrombectomy.

MATERIALS AND METHODS

This retrospective study included all patients aged over 18 years with an anterior circulation stroke treated at a thrombectomy centre from 2010 to 2020 with external validation. The primary outcome was day 90 mRS ≥3. Existing clinical scores (SPAN and PRE) and Machine Learning (ML) models were compared. A novel clinical score (iSPAN) was derived by adding an optimised weighting of the most important ML features to the SPAN.

RESULTS

812 patients were initially included (397 female, average age 73), 63 for external validation. The best performing clinical score and ML model were SPAN and XGB (sensitivity, specificity and accuracy 0.290, 0.967, 0.628 and 0.693, 0.783, 0.738 respectively). A significant difference was found overall and our XGB model was more accurate than SPAN (p < 0.0018). The most important features were Age, mTICI and total number of passes. The addition of 11 points for mTICI of ≤2B and 3 points for ≥3 passes to the SPAN achieved the best accuracy and was used to create the iSPAN. iSPAN was not significantly less accurate than our XGB model (p > 0.5). In the external validation set, iSPAN and SPAN achieved sensitivity, specificity, and accuracy of (0.735, 0.862, 0.79) and (0.471, 0.897, 0.67) respectively.

CONCLUSION

iSPAN incorporates machine-derived features to achieve better predictions compared to existing clinical scores. It is not inferior to our XGB model and is externally generalisable.

Effect of Clot Burden Score on Safety and Efficacy of Intravenous Alteplase Prior to Mechanical Thrombectomy in Acute Ischemic Stroke: A Subgroup Analysis of a Randomized Phase 3 Trial

BACKGROUND AND PURPOSE

Whether thrombus burden in acute ischemic stroke modify the effect of intravenous thrombolysis (IVT) before mechanical thrombectomy (MT) remains uncertain. We aim to investigate the treatment effect of stratified clot burden score (CBS) on the efficacy and safety of direct versus bridging MT.

MATERIALS AND METHODS

This is an exploratory subgroup analysis of a randomized trial evaluating the effect of CBS on clinical outcome in the DIRECT-MT trial. CBS was divided into 3 groups (0-3, 4-6, and 7-10) based on preoperative CTA, where higher scores indicated a lower clot burden. We report the adjusted common odds ratio for a shift toward better outcomes on the mRS after thrombectomy alone compared with combination treatment by stratified CBS groups.

RESULTS

No modification effect of mRS distribution was observed by CBS subgroups (CBS 0-3: adjusted common ratio odds 1.519 [95% CI, 0.928-2.486]; 4-6: 0.924 [0.635-1.345]; 7-10: 1.040 [0.481-2.247]). Patients with CBS 4-6 had a higher rate of early reperfusion (adjusted OR (aOR), 0.3 [95% CI, 0.1-0.9]), final reperfusion (aOR 0.5 [95% CI, 0.3-0.9]), and fewer thrombectomy attempts (aOR 0.4 [95% CI, 0.1-0.7]). Patients with CBS 7-10 had a higher rate of asymptomatic intracranial hemorrhage (14.9% versus 36.8%, P = .0197) for bridging MT. No significant difference was observed in other safety outcomes by trichotomized CBS.

CONCLUSIONS

The subgroup analysis of DIRECT-MT suggested that thrombus burden did not alter the treatment effect of IVT before MT on functional outcomes in CBS subgroups.

Electrical impedance measurements can identify red blood cell-rich content in acute ischemic stroke clots ex vivo associated with first-pass successful recanalization

Background

Electrochemical impedance spectroscopy can determine characteristics such as cell density, size, and shape. The development of an electrical impedance-based medical device to estimate acute ischemic stroke (AIS) clot characteristics could improve stroke patient outcomes by informing clinical decision making.

Objectives

To assess how well electrical impedance combined with machine learning identified red blood cell (RBC)-rich composition of AIS clots ex vivo, which is associated with a successfully modified first-pass effect.

Methods

A total of 253 clots from 231 patients who underwent thrombectomy in 5 hospitals in France, Japan, Serbia, and Spain between February 2021 and October 2023 were analyzed in the Clotbase International Registry. Electrical impedance measurements were taken following clot retrieval by thrombectomy, followed by Martius Scarlet Blue staining. The clot components were quantified via Orbit Image Analysis, and RBC percentages were correlated with the RBC estimations made by the electrical impedance machine learning model.

Results

Quantification by Martius Scarlet Blue staining identified RBCs as the major component in clots (RBCs, 37.6%; white blood cells, 5.7%; fibrin, 25.5%; platelets/other, 30.3%; and collagen, 1%). The impedance-based RBC estimation correlated well with the RBC content determined by histology, with a slope of 0.9 and Spearman's correlation of r = 0.7. Clots removed in 1 pass were significantly richer in RBCs and clots with successful recanalization in 1 pass (modified first-pass effect) were richer in RBCs as assessed using histology and impedance signature.

Conclusion

Electrical impedance estimations of RBC content in AIS clots are consistent with histologic findings and may have potential for clinically relevant parameters.

Thrombolytic therapy based on lyophilized platelet-derived nanocarriers for ischemic stroke

BACKGROUND

Intravenous administration of fibrinolytic drugs, such as recombinant tissue plasminogen activator (rtPA) is the standard treatment of acute thrombotic diseases. However, current fibrinolytics exhibit limited clinical efficacy because of their short plasma half-lives and risk of hemorrhagic transformations. Platelet membrane-based nanocarriers have received increasing attention for ischemic stroke therapies, as they have natural thrombus-targeting activity, can prolong half-life of the fibrinolytic therapy, and reduce side effects. In this study we have gone further in developing platelet-derived nanocarriers (defined as cellsomes) to encapsulate and protect rtPA from degradation. Following lyophilization and characterization, their formulation properties, biocompatibility, therapeutic effect, and risk of hemorrhages were later investigated in a thromboembolic model of stroke in mice.

RESULTS

Cellsomes of 200 nm size and loaded with rtPA were generated from membrane fragments of human platelets. The lyophilization process did not influence the nanocarrier size distribution, morphology, and colloidal stability conferring particle preservation and long-term storage. Encapsulated rtPA in cellsomes and administered as a single bolus showed to be as effective as a continuous clinical perfusion of free rtPA at equal concentration, without increasing the risk of hemorrhagic transformations or provoking an inflammatory response.

CONCLUSIONS

This study provides evidence for the safe and effective use of lyophilized biomimetic platelet-derived nanomedicine for precise thrombolytic treatment of acute ischemic stroke. In addition, this new nanoformulation could simplify the clinical use of rtPA as a single bolus, being easier and less time-consuming in an emergency setting than a treatment perfusion, particularly in stroke patients. We have successfully addressed one of the main barriers to drug application and commercialization, the long-term storage of nanomedicines, overcoming the potential chemical and physical instabilities of nanomedicines when stored in an aqueous buffer.

Bridging Thrombolysis Before Endovascular Therapy in Stroke Patients With Faster Core Growth

BACKGROUND AND OBJECTIVES

It is still uncertain that going direct to endovascular thrombectomy (EVT) leads to equivalent outcomes as bridging IV thrombolysis (IVT) in acute ischemic patients. This study aimed to explore whether the rate of ischemic core growth influenced the patient outcomes after bridging IVT vs direct EVT.

METHODS

This was a retrospective cohort study based on the International Stroke Perfusion Imaging Registry (INSPIRE). It selected acute ischemic stroke patients receiving perfusion CT within 4.5 hours of stroke onset. Patients who went direct to EVT were compared with those who received bridging treatment of IVT before EVT. Ischemic core growth rate was estimated by the acute ischemic core volume on perfusion CT divided by the time from stroke onset to perfusion CT, based on the assumption of a linear growth pattern of ischemic core. Core growth rate was stratified into fast (>15 mL/h) and slow (≤15 mL/h), based on its interaction with bridging IVT in predicting the primary outcome. The primary outcome was modified Rankin scale of 0-2 at 3 months. The secondary outcomes included successful thrombectomy reperfusion defined by modified Thrombolysis in Cerebral Infarction score of 2b-3 and time from groin puncture to reperfusion.

RESULTS

Of the 1,221 EVT patients in the INSPIRE, 323 patients were selected, of which 82 patients received direct EVT and 241 patients received bridging IVT. Bridging IVT was associated with a higher rate of good clinical outcome among patients with fast core growth (39% vs 7% for direct EVT, odds ratio [OR] 8.75 [1.96-39.1], p = 0.005), but the difference was not notable for patients with slow core growth (55% vs 55% for direct EVT, OR 1.00 [0.53-1.87], p = 0.989). In patients with fast core growth, the bridging and direct EVT patients showed no difference in the reperfusion rate (80% vs 76%, p = 0.616). However, patients who received bridging IVT were more likely to achieve reperfusion earlier (the median groin to reperfusion time of 63.0 vs 94.0 minutes, p = 0.005).

DISCUSSION

Patients with fast core growth were more likely to benefit from bridging IVT. This is likely because prior IVT facilitates clot removal and thus reduces time to reperfusion.

Thrombus composition and thrombolysis resistance in stroke

A State of the Art lecture titled "Thrombus Composition and Thrombolysis Resistance in Stroke" was presented at the ISTH Congress in 2022. Intravenous thrombolysis (IVT) remains the only pharmacologic option to re-establish cerebral perfusion at the acute phase of ischemic stroke. IVT is based on the administration of recombinant tissue plasminogen activator with the objective of dissolving fibrin, the major fibrillar protein component of thrombi. Almost 30 years on from its introduction, although the clinical benefits of IVT have been clearly demonstrated, IVT still suffers from a relatively low efficacy, with a rate of successful early recanalization below 50% overall. Analyses of thrombectomy-recovered acute ischemic stroke (AIS) thrombi have shown that apart from occlusion site, thrombus length, and collateral status, AIS thrombus structure and composition are also important modulators of IVT efficacy. In this article, after a brief presentation of IVT principle and current knowledge on IVT resistance, we review recent findings on how compaction and structural alterations of fibrin together with nonfibrin thrombus components such as neutrophil extracellular traps and von Willebrand factor interfere with IVT in AIS. We further discuss how these new insights could soon result in the development of original adjuvant therapies for improved IVT in AIS. Finally, we summarize relevant new data presented during the 2022 ISTH Congress.

S100b in acute ischemic stroke clots is a biomarker for post-thrombectomy intracranial hemorrhages

Background and purpose

Post-thrombectomy intracranial hemorrhages (PTIH) are dangerous complications of acute ischemic stroke (AIS) following mechanical thrombectomy. We aimed to investigate if S100b levels in AIS clots removed by mechanical thrombectomy correlated to increased risk of PTIH.

Methods

We analyzed 122 thrombi from 80 AIS patients in the RESTORE Registry of AIS clots, selecting an equal number of patients having been pre-treated or not with rtPA (40 each group). Within each subgroup, 20 patients had developed PTIH and 20 patients showed no signs of hemorrhage. Gross photos of each clot were taken and extracted clot area (ECA) was measured using ImageJ. Immunohistochemistry for S100b was performed and Orbit Image Analysis was used for quantification. Immunofluorescence was performed to investigate co-localization between S100b and T-lymphocytes, neutrophils and macrophages. Chi-square or Kruskal-Wallis test were used for statistical analysis.

Results

PTIH was associated with higher S100b levels in clots (0.33 [0.08-0.85] vs. 0.07 [0.02-0.27] mm², H1 = 6.021, P = 0.014^*), but S100b levels were not significantly affected by acute thrombolytic treatment (P = 0.386). PTIH was also associated with patients having higher NIHSS at admission (20.0 [17.0-23.0] vs. 14.0 [10.5-19.0], H1 = 8.006, P = 0.005) and higher number of passes during thrombectomy (2 [1-4] vs. 1 [1-2.5], H1 = 5.995, P = 0.014^*). S100b co-localized with neutrophils, macrophages and with T-lymphocytes in the clots.

Conclusions

Higher S100b expression in AIS clots, higher NIHSS at admission and higher number of passes during thrombectomy are all associated with PTIH. Further investigation of S100b expression in AIS clots by neutrophils, macrophages and T-lymphocytes could provide insight into the role of S100b in thromboinflammation.

Direct Mechanical Thrombectomy Versus Prior Bridging Intravenous Thrombolysis in Acute Ischemic Stroke: A Systematic Review and Meta-Analysis

BACKGROUND

The current guideline recommends using an intravenous tissue-type plasminogen activator (IV tPA) prior to mechanical thrombectomy (MT) in eligible acute ischemic stroke (AIS) with emergent large vessel occlusion (ELVO). Some recent studies found no significant differences in the long-term functional outcomes between bridging therapy (BT, i.e., IV tPA prior to MT) and direct MT (dMT).

METHODS

We conducted a systematic review and meta-analysis to compare the safety and functional outcomes between BT and dMT in AIS patients with ELVO who were eligible for IV tPA administration. Based on the ELVO location, patients were categorized as the anterior group (occlusion of the anterior circulation), or the combined group (occlusion of the anterior and/or posterior circulation). A subgroup analysis was performed based on the study type, i.e., RCT and non-RCT.

RESULTS

Thirteen studies (3985 patients) matched the eligibility criteria. Comparing the BT and dMT groups, no significant differences in terms of mortality and good functional outcome were observed at 90 days. Symptomatic intracranial hemorrhagic (sICH) events were more frequent in BT patients in the combined group (OR = 0.73, p = 0.02); this result remained significant only in the non-RCT subgroup (OR = 0.67, p = 0.03). The RCT subgroup had a significantly higher rate of successful revascularization in BT patients (OR = 0.73, p = 0.02).

CONCLUSIONS

Our meta-analysis uncovered no significant differences in functional outcome and mortality rate at 90 days between dMT and BT in patients with AIS who had ELVO. Although BT performed better in terms of successful recanalization rate, there is a risk of increased sICH rate in this group.

Effect of intravenous thrombolysis on core growth rate in patients with acute cerebral infarction

Objective

This study aimed to investigate the effects of recombinant tissue plasminogen activator intravenous thrombolysis (IVT) on the core growth rate of acute ischemic stroke.

Methods

Stroke patients with large vessel occlusion and non-recanalization from IVT treatment were retrospectively included in this study and divided into two groups: IVT and non-IVT. The core growth rate was estimated by the acute core volume on perfusion CT divided by the last known well time from stroke to CT perfusion. The primary endpoint was the core growth rate, the tissue outcome was 24 h-ASPECTS, and the clinical outcome was a 3-month modified Rankin score.

Results

A total of 94 patients were included with 53 in the IVT group and 41 in the non-IVT group. There was no significant difference in age, gender, hypertension, diabetes, atrial fibrillation, acute NIHSS, and last known well time from stroke to CT perfusion acquisition between the two groups. The core growth rate in the IVT group was lower than that in the non-IVT group, which was statistically significant after multivariate adjustment (coefficient: -5.20, 95% CI= [-9.85, -0.56], p = 0.028). There was a significant interaction between the IVT and the collateral index in predicting the core growth rate. The analysis was then stratified according to the collateral index, and the results suggested that IVT reduced the core growth rate more significantly after the worsening of collateral circulation (coefficient: 15.38, 95% CI= [-26.25, -4.40], p = 0.007). The 3-month modified Rankin score and 24 h-ASPECTS were not statistically significant between the two groups.

Conclusion

Intravenous thrombolysis reduces the core growth rate in patients with AIS, especially those with poor collateral status.

Fibrin-Targeted Nanoparticles for Finding, Visualizing and Characterizing Blood Clots in Acute Ischemic Stroke

Recanalization of the occluded artery is the gold standard treatment for acute ischemic stroke, which includes enzymatic fibrinolytic treatment with the use of recombinant tissue plasminogen activators (rtPAs) to disrupt the occluding clot, the use of mechanical thrombectomy to physically remove the clot, or a combination of both. Fibrin is one of the main components of blood clots causing ischemic stroke and is the target of rtPA upon activation of plasminogen in the clot. In addition, fibrin content also influences the efficacy of mechanical thrombectomy. Current imaging methods can successfully identify occlusions in large vessels; however, there is still a need for contrast agents capable of visualizing small thrombi in ischemic stroke patients. In this work, we describe the synthesis and the in vitro characterization of a new diagnostic nanoparticle, as well as the in vivo evaluation in an animal model of thromboembolic stroke. Gd-labeled KCREKA peptides were synthesized and attached onto the surface of PEGylated superparamagnetic nanoparticles. Magnetic resonance imaging (MRI) of blood clots was performed in vitro and in vivo in animal models of thromboembolic stroke. KCREKA-NPs were synthesized by attaching the peptide to the amino (N) termini of the PEG-NPs. The sizes of the nanoparticles, measured via DLS, were similar for both KCREKA-NPs and PEG-NPs (23 ± 4 nm, PDI = 0.11 and 25 ± 8 nm, PDI = 0.24, respectively). In the same line, r2 relaxivities were also similar for the nanoparticles (149 ± 2 mM Fe s−1 and 151 ± 5 mM Fe s−1), whereas the r1 relaxivity was higher for KCREKA-NPs (1.68 ± 0.29 mM Fe s−1 vs. 0.69 ± 0.3 mM Fe s−1). In vitro studies showed that blood clots with low coagulation times were disrupted by rtPA, whereas aged clots were almost insensitive to the presence of rtPA. MRI in vitro studies showed a sharp decrease in the T1 × T2 signals measured for aged clots incubated with KCREKA-NPs compared with fresh clots (47% [22, 80] to 26% [15, 51]). Furthermore, the control blood showed a higher value of the T1 × T2 signal (39% [20, 61]), being the blood clots with low coagulation times the samples with the lowest values measured by MRI. In vivo studies showed a significant T1 × T2 signal loss in the clot region of 24% after i.v. injection of KCREKA-NPs. The thrombus age (2.5% ± 6.1% vs. 81.3% ± 19.8%, p < 0.01) confirmed our ability to identify in vivo fresh blood clots. In this study, we developed and tested a dual MRI nanoparticle, acting as T1 and T2 contrast agents in MRI analyses. The developed KCREKA-NPs showed affinity for the fibrin content of blood clots, and the MRI signals provided by the nanoparticles showed significant differences depending on the clot age. The developed KCREKA-NPs could be used as a tool to predict the efficacy of a recanalization treatment and improve the triage of ischemic stroke patients.

Detection, Diagnosis and Treatment of Acute Ischemic Stroke: Current and Future Perspectives

Stroke is one of the leading causes of disability worldwide. Early diagnosis and treatment of stroke are important for better clinical outcome. Rapid and accurate diagnosis of stroke subtypes is critical. This review discusses the advantages and disadvantages of the current diagnostic and assessment techniques used in clinical practice, particularly for diagnosing acute ischemic stroke. Alternative techniques for rapid detection of stroke utilizing blood based biomarkers and novel portable devices employing imaging methods such as volumetric impedance phase-shift spectroscopy, microwave tomography and Doppler ultrasound are also discussed. Current therapeutic approaches for treating acute ischemic stroke using thrombolytic drugs and endovascular thrombectomy are discussed, with a focus on devices and approaches recently developed to treat large cranial vessel occlusions.

Intravenous thrombolysis prior to mechanical thrombectomy does not affect clinical or procedural outcomes in patients with large vessel occlusion acute ischemic stroke

Mechanical thrombectomy (MT) has revolutionized the care of large vessel occlusion acute ischemic strokes (LVOAIS). However, the benefit of intravenous thrombolysis prior to MT remains unproven. Two recent trials showed equivocal results regarding the benefits of pre-MT intravenous thrombolysis in predominantly Asian populations. We evaluated clinical outcomes and procedural metrics for patients with LVOAIS who were treated with MT alone compared to those who were treated with both intravenous tPA and MT. In a retrospective study, LVOAIS patients treated with MT, with or without preceding intravenous thrombolysis, between January of 2017 and December of 2019 were identified. Patients were treated according to contemporary guidelines. Baseline demographic and clinical characteristics, procedural metrics, and clinical outcomes were collected. Among LVOAIS patients, those treated with intravenous thrombolysis and MT did not differ from those with MT alone on clinical outcomes at three months. Further, the two groups did not differ on thrombectomy procedure times, recanalization rates, and symptomatic intracranial hemorrhage rates. In our patients with LVOAIS, intravenous thrombolysis combined with MT offered no advantage compared to MT alone in clinical outcomes or recanalization rates. Our results are consistent with earlier studies in other populations. In addition, our results suggest that IV tPA does not impact the ease of clot removal by MT. Further studies will evaluate how newly available thrombolytic agents may benefit patients eligible for MT.

Histological composition of retrieved emboli in acute ischemic stroke is independent of pre-thrombectomy alteplase use

BACKGROUND AND PURPOSE

Given recent evidence suggesting the clot composition may be associated with revascularization outcomes and stroke etiology, clot composition research has been a topic of growing interest. It is currently unclear what effect, if any, pre-thrombectomy thrombolysis has on clot composition. Understanding this association is important as it is a potential confounding variable in clot composition research. We retrospectively evaluated the composition of retrieved clots from ischemic stroke patients who did and did not receive pre-treatment tPA to study the effect of tPA on clot composition.

MATERIALS AND 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 Scarlett Blue (MSB) staining and area of the clot was also measured on the gross photos. Student's t test was used for continuous variables and chi-squared test for categorical variables.

RESULTS

A total of 1430 patients were included in this study. Mean age was 68.4±13.5 years. Overall rate of TICI 2c/3 was 67%. A total of 517 patients received tPA (36%) and 913 patients did not (64%). Mean RBC density for the tPA group was 42.97±22.62% compared to 42.80±23.18% for the non-tPA group (P=0.89). Mean WBC density for the tPA group was 3.74±2.60% compared to 3.42±2.21% for the non-tPA group (P=0.012). Mean fibrin density for the tPA group was 26.52±15.81% compared to 26.53±15.34% for the non-tPA group (P=0.98). Mean platelet density for the tPA group was 26.22±18.60% compared to 26.55±19.47% for the non-tPA group (P=0.75). tPA group also had significantly smaller clot area compared to non-tPA group.

CONCLUSIONS

Our study 1430 retrieved emboli and ischemic stroke patients shows no interaction between tPA administration and clot composition. These findings suggest that tPA does not result in any histological changes in clot composition.

Does prior administration of rtPA influence acute ischemic stroke clot composition? Findings from the analysis of clots retrieved with mechanical thrombectomy from the RESTORE registry

BACKGROUND AND PURPOSE

There is still much debate whether bridging-therapy [intravenous thrombolysis (IVT) prior to mechanical thrombectomy (MT)] might be beneficial compared to MT alone. We investigated the effect of IVT on size and histological composition of the clots retrieved from patients undergoing bridging-therapy or MT alone.

METHODS

We collected mechanically extracted thrombi from 1000 acute ischemic stroke (AIS) patients included in RESTORE registry. Patients were grouped according to the administration (or not) of IVT before thrombectomy. Gross photos of each clot were taken and Extracted Clot Area (ECA) was measured using ImageJ software. Martius Scarlett Blue stain was used to characterize the main histological clot components [red blood cells (RBCs), fibrin (FIB), platelets/other (PTL)] and Orbit Image Analysis was used for quantification. Additionally, we calculated the area of each main component by multiplying the component percent by ECA. Chi-squared and Kruskal-Wallis tests were used for statistical analysis.

RESULTS

451 patients (45%) were treated with bridging-therapy while 549 (55%) underwent MT alone. When considering only percent histological composition, we did not find any difference in RBC% (P = 0.895), FIB% (P = 0.458) and PTL% (P = 0.905). However, bridging-therapy clots were significantly smaller than MT-alone clots [32.7 (14.8-64.9) versus 36.8 (20.1-79.8) mm2, N = 1000, H1 = 7.679, P = 0.006*]. A further analysis expressing components per clot area showed that clots retrieved from bridging-therapy cases contained less RBCs [13.25 (4.29-32.06) versus 14.97 (4.93-39.80) mm2, H1 = 3.637, P = 0.056] and significantly less fibrin [9.10 (4.62-17.98) versus 10.54 (5.57-22.48) mm2, H1 = 7.920, P = 0.005*] and platelets/other [5.04 (2.26-11.32) versus 6.54 (2.94-13.79) mm2, H1 = 9.380, P = 0.002*] than MT-alone clots.

CONCLUSIONS

Our results suggest that previous IVT administration significantly reduces thrombus size, proportionally releasing all the main histological components.

Direct to angiography suite approaches for the triage of suspected acute stroke patients: a systematic review and meta-analysis

Background:

Increasing evidence suggests improved time metrics leading to better clinical outcomes when stroke patients with suspected large vessel occlusion (LVO) are transferred directly to the angiography suite (DTAS) compared with cross-sectional imaging followed by transfer to the angiography suite. We performed a systematic review and meta-analysis on the efficacy and safety of DTAS approaches.

Methods:

We searched Embase, Medline, Scopus, and clinicaltrials.gov for studies comparing outcomes of DTAS and conventional triage. Eligible studies were assessed for risk of bias. We performed a random-effects meta-analysis on the differences of median door-to-groin and door-to-reperfusion times between intervention and control group. Secondary outcomes included good outcome at 90 days (modified Rankin Scale ⩽ 2) rate of symptomatic intracranial hemorrhage (sICH) and mortality within 90 days.

Results:

Eight studies (one randomized, one cluster-randomized trial and six observational studies) with 1938 patients were included. Door-to-groin and door-to-reperfusion times in the intervention group were on median 29.0 min [95% confidence interval (CI): 14.3–43.6; p < 0.001] and 32.1 min (95% CI: 15.1–49.1; p < 0.001) shorter compared with controls. Prespecified subgroup analyses for transfer (n = 1753) and mothership patients (n = 185) showed similar reductions of the door-to-groin and door-to-reperfusion times in response to the intervention. The odds of good outcome did not differ significantly between both groups but were numerically higher in the intervention group (odds ratio: 1.38, 95% CI: 0.97–1.95; p = 0.07). There was no significant difference for mortality and sICH between the groups.

Conclusion:

DTAS approaches for the triage of suspected LVO patients led to a significant reduction in door-to-groin and door-to-reperfusion times but an effect on functional outcome was not detected. The subgroup analysis showed similar results for transfer and mothership patients.

Registration: This study was registered in PROSPERO (CRD42020213621).

Aspects of ischemic stroke biomechanics derived using ex-vivo and in-vitro methods relating to mechanical thrombectomy

Establishing the underlying biomechanics of acute ischemic stroke (AIS) and its treatment is fundamental to developing more effective clinical treatments for one of society's most impactful diseases. Recent changes in AIS management, driven by clinical evidence of improved treatments, has already led to a rapid rate of innovation, which is likely to be sustained for many years to come. These unprecedented AIS triage and treatment innovations provide a great opportunity to better understand the disease. In this article we provide a perspective on the recreation of AIS in the laboratory to inform contemporary device design and procedural techniques in mechanical thrombectomy. Presentation of these findings, which have been used to solve the applied problem of designing mechanical thrombectomy devices, is intended to help inform the development of basic biomechanics solutions for AIS.

Correlation between acute ischaemic stroke clot length before mechanical thrombectomy and extracted clot area: Impact of thrombus size on number of passes for clot removal and final recanalization

Introduction

We assessed the correlation between thrombus size before and after mechanical thrombectomy, measured as length by Computed Tomography Angiography/Non-Contrast Computed Tomography (CTA/NCCT) and Extracted Clot Area, ECA, respectively. We also assessed the influence of thrombus size on the number of passes required for clot removal and final recanalization outcome.

Materials and methods

Acute ischaemic stroke (AIS) thrombi retrieved by mechanical thrombectomy from 500 patients and data of clot length by CTA/NCCT were collected from three hospitals in Europe. ECA was obtained by measuring the area of the extracted clot. Non-parametric tests were used for data analysis.

Results

A strong positive correlation was found between clot length on CTA/NCCT and ECA (rho = 0.619,N = 500,P < 0.0001*). Vessel size influences clot length on CTA/NCCT (H2 = 98.6, P < 0.0001*) and ECA (H2 = 105.6,P < 0.0001*), but the significant correlation between CTA/NCCT length and ECA was evident in all vessels. Poorer revascularisation outcome was associated with more passes (H5 = 73.1, P < 0.0001*). More passes were required to remove longer clots (CTA/NCCT; H4 = 31.4, P < 0.0001*; ECA; H4 = 50.2, P < 0.0001*). There was no significant main association between recanalization outcome and length on CTA/NCCT or ECA, but medium sized clots (ECA 20–40 mm²) were associated with least passes and highest revascularisation outcome (N = 500, X² = 16.2, P < 0.0001*).

Conclusion

Clot length on CTA/NCCT strongly correlates with ECA. Occlusion location influences clot size. More passes are associated with poorer revascularisation outcome and bigger clots. The relationship between size and revascularisation outcome is more complex. Clots of medium ECA take less passes to remove and are associated with better recanalization outcome than both smaller and larger clots.

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

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

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

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

Safety and Outcomes of Thrombectomy in Ischemic Stroke With vs Without IV Thrombolysis

OBJECTIVE

To test the hypothesis that IV thrombolysis (IVT) treatment before endovascular thrombectomy (EVT) is associated with better outcomes in patients with anterior circulation large artery occlusion (LAO) stroke, we examined a large real-world database, the Safe Implementation of Treatment in Stroke-International Stroke Thrombectomy Register (SITS-ISTR).

METHODS

We identified centers recording ≥10 consecutive patients in the SITS-ISTR, with at least 70% available modified Rankin Scale (mRS) scores at 3 months during 2014 to 2019. We defined LAO as intracranial internal carotid artery, first and second segment of middle cerebral artery, and first segment of anterior cerebral artery. Main outcomes were functional independence (mRS score 0-2) and death at 3 months and symptomatic intracranial hemorrhage (SICH) per modified SITS-Monitoring Study. We performed propensity score-matched (PSM) and multivariable logistic regression analyses.

RESULTS

Of 6,350 patients from 42 centers, 3,944 (62.1%) received IVT. IVT + EVT-treated patients had less frequent atrial fibrillation, ongoing anticoagulation, previous stroke, heart failure, and prestroke disability. PSM analysis showed that IVT + EVT-treated patients had a higher rate of functional independence than patients treated with EVT alone (46.4% vs 40.3%, p < 0.001) and a lower rate of death at 3 months (20.3% vs 23.3%, p = 0.035). SICH rates (3.5% vs 3.0%, p = 0.42) were similar in both groups. Multivariate adjustment yielded results consistent with PSM.

CONCLUSION

Pretreatment with IVT was associated with favorable outcomes in EVT-treated LAO stroke in the SITS-ISTR. These findings, while indicative of international routine clinical practice, are limited by observational design, unmeasured confounding, and possible residual confounding by indication.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that IVT before EVT increases the probability of functional independence at 3 months compared to EVT alone.

Histological evaluation of acute ischemic stroke thrombi may indicate the occurrence of vessel wall injury during mechanical thrombectomy

Background

Several animal studies have demonstrated that mechanical thrombectomy (MT) for acute ischemic stroke (AIS) may cause vessel wall injury (VWI). However, the histological changes in human cerebral arteries following MT are difficult to determine.

Objective

To investigate the occurrence of VWI during MT by histological and immunohistochemical evaluation of AIS clots.

Methods

As part of the multicenter STRIP registry, 277 clots from 237 patients were analyzed using Martius Scarlett Blue stain and immunohistochemistry for CD34 (endothelial cells) and smooth muscle actin (smooth muscle cells).

Results

MT devices used were aspiration catheters (100 cases), stentriever (101 cases), and both (36 cases). VWI was found in 33/277 clots (12%). There was no significant correlation between VWI and MT device. The degree of damage varied from grade I (mild intimal damage, 24 clots), to grade II (relevant intimal and subintimal damage, 3 clots), and III (severe injury, 6 clots). VWI clots contained significantly more erythrocytes (p=0.006*) and less platelets/other (p=0.005*) than non-VWI clots suggesting soft thrombus material.

Thrombolysis correlated with a lower rate of VWI (p=0.04*). VWI cases showed a significantly higher number of passes (2 [1–4] vs 1 [1–3], p=0.028*) and poorer recanalization outcome (p=0.01*) than cases without VWI.

Conclusions

Histological markers of VWI were present in 12% of AIS thrombi, suggesting that VWI might be related to MT. VWI was associated with soft thrombus consistency, higher number of passes and poorer revascularization outcome. There was no significant correlation between VWI and MT device.

Functional Outcome After Mechanical Thrombectomy with or without Previous Thrombolysis

INTRODUCTION

Combined intravenous therapy (IVT) and mechanical thrombectomy (MT) is the standard treatment for acute ischemic stroke (AIS) with large vessel occlusion (LVO). However, the use of  IVT before MT is recently being questioned.

OBJECTIVES

To compare patients treated with IVT before MT with those treated with MT alone, in a real-world scenario.

METHODS

Retrospective analysis of AIS patients with LVO of the anterior circulation who underwent MT, with or without previous IVT, between 2016 and 2018.

RESULTS

A total of 524 patients were included (347 submitted to IVT+MT; 177 to MT alone). No differences between groups were found except for a higher time from stroke onset to CT and to groin puncture in the MT group (297.5 min vs 115.0 min and 394.0 min vs 250.0 min respectively, p < 0.001). Multivariable analysis showed that age<75 years (OR 2.65, 95% CI 1.71-4.07, p < 0.001), not using antiplatelet therapy (OR 1.93, 95% CI 1.21-3.08, p = 0.006), low prestroke mRS (OR 4.33, 95% CI 1.89-9.89, p < 0.001), initial NIHSS (OR 0.89, 95% CI 0.86-0.93, p < 0.001), absent cerebral edema (OR 7.83, 95% CI 3.31-18.51, p < 0.001), and mTICI 2b/3 (OR 4.56, 95% CI 2.17-9.59, p < 0.001) were independently associated with good outcome (mRS 0-2).

CONCLUSIONS

Our findings support the idea that IVT before MT does not influence prognosis, in a real-world setting.