Adjunct Thrombolysis Enhances Brain Reperfusion following Successful Thrombectomy

Hippocampal neurometabolic and structural changes from pre-to post-COVID-19: A case-series study

BACKGROUND

Neurological complications of the COVID-19 infection may be caused in part by local neurochemical and structural abnormalities that could not be detected during routine medical examinations. We examined within subject neurometabolic and structural brain alterations from pre-to post-COVID-19 in the hippocampal region of three elderly individuals (aged 63-68 years) who had a COVID-19 infection with mild symptoms. Patients were participating in an interventional study in which they were closely monitored at the time they were diagnosed with COVID-19. Patients 1 and 2 just completed 18-20 resistance training sessions prior to their diagnosis. Patient 3 was assigned to a non-training condition in the same study.

METHODS

Whole brain magnetic resonance imaging (MRI) images and proton magnetic resonance spectroscopy (1H-MRS) of the left hippocampus were collected before and after infection. Structural and spectroscopic imaging measures post-COVID-19 were contrasted to the pre-COVID-19 measures and were compared with values for Minimal Detectable Change at 95% (MDC95) and 90% (MDC90) confidence from a group of six elderly (aged 60-79 years) without COVID-19 that participated in the same study.

RESULTS

After SARS-COV-2 infection, we observed a reduction of glutamate-glutamine (Glx) in Patients 1 and 2 (≥ 42.0%) and elevation of myo-inositol (mIns) and N-acetyl-aspartate (NAA) in Patient 3 (≥ 36.4%); all > MDC90. MRI findings showed increased (Patients 1 and 2) or unchanged (Patient 3) hippocampal volume.

CONCLUSIONS

Overall, findings from this exploratory study suggest that mild COVID-19 infection could be associated with development of local neuroinflammation and reduced glutamate levels in the hippocampus. Our 1H-MRS findings may have clinical value for explaining chronic neurological and psychological complaints in COVID-19 long-haulers.

Intravenous Thrombolysis before Complete Angiographic Reperfusion: Beyond Angiographic Assessment to Target Microvascular Obstruction?

OBJECTIVE

Recent data have suggested that ineffective tissue reperfusion despite successful angiographic reperfusion was partly responsible for unfavorable outcomes after endovascular therapy (EVT) and might be modulated by intravenous thrombolysis (IVT) use before EVT. To specifically decipher the effect played by IVT before EVT, we compared the clinical and safety outcomes of patients who experienced a complete reperfusion at the end of EVT according to IVT use before EVT.

METHODS

The Endovascular Treatment in Ischemic Stroke (ETIS) registry is an ongoing, prospective, observational study at 21 centers that perform EVT in France. Patients were included if they had an anterior large vessel occlusion of the intracranial internal carotid artery or middle cerebral artery (M1/M2 segments) and complete reperfusion (expanded Thrombolysis in Cerebral Infarction score = 3) with EVT within 6 hours, between January 2015 and December 2021. The cohort was divided into two groups according to IVT use before EVT, and propensity score matching (PSM) was used to balance the two groups. Primary outcome was the shift in the degree of disability as measured by the modified Rankin Scale (mRS) at 90 days. Secondary outcomes included favorable outcome (mRS 0-2) at 90 days. Safety outcomes included symptomatic intracranial hemorrhage and 90-day mortality. Outcomes were estimated with multivariate logistic models adjusted for age, National Institutes of Health Stroke Scale, Alberta Stroke Program Early CT Score, and time from symptom onset to puncture.

RESULTS

Among 5,429 patients included in the ETIS registry, 1,093 were included in the study, including 651 patients with complete recanalization treated with IVT before EVT. After PSM, 488 patients treated with IVT before EVT were compared to 337 patients without IVT. In the matched cohort analysis, the IVT+EVT group had a favorable shift in the overall mRS score distribution (adjusted odds ratio [aOR] = 1.41, 95% confidence interval [CI] = 1.04-1.91, p = 0.023) and higher rates of favorable outcome (61.1% vs 48.7%, aOR = 1.49, 95% CI = 1.02-2.20, p = 0.041) at 90 days compared with the EVT alone group. Rates of symptomatic intracerebral hemorrhage were comparable between both groups (6.0% vs 4.3%, aOR = 1.16, 95% CI = 0.53-2.54, p = 0.709).

INTERPRETATION

In clinical practice, even after complete angiographic reperfusion by EVT, prior IVT use improves clinical outcomes of patients without increasing bleeding risk. ANN NEUROL 2024;95:762-773.

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.

New Perspectives in Neuroprotection for Ischemic Stroke

The constant failure of new neuroprotective therapies for ischemic stroke has partially halted the search for new therapies in recent years, mainly because of the high investment risk required to develop a new treatment for a complex pathology, such as stroke, with a narrow intervention window and associated comorbidities. However, owing to recent progress in understanding the stroke pathophysiology, improvement in patient care in stroke units, development of new imaging techniques, search for new biomarkers for early diagnosis, and increasingly widespread use of mechanical recanalization therapies, new opportunities have opened for the study of neuroprotection. This review summarizes the main protective agents currently in use, some of which are already in the clinical evaluation phase. It also includes an analysis of how recanalization therapies, new imaging techniques, and biomarkers have improved their efficacy.

Systemic Immune-Inflammation Response is Associated with Futile Recanalization After Endovascular Treatment

BACKGROUND

Frequent incidence of futile recanalization decreases the benefit of endovascular treatment (EVT) in acute ischemic stroke. We hypothesized that the inflammation and immune response after ischemic are associated with futile recanalization. We aimed to investigate the correlation of admission systemic immune-inflammation index (SII) with futile recanalization post EVT.

METHODS

Patients with successful recanalization (modified Thrombolysis in Cerebral Ischemia angiographic score 2b-3) and maintained artery recanalized after 24 h of EVT were chosen from a prospective nationwide registry study. Futile recanalization was defined as a poor functional outcome (modified Rankin Scale score 3-6) at 90 days, irrespective of a successful recanalization. At admission, SII was calculated as (platelet count × neutrophil count)/lymphocyte count/100. Logistic regression analysis helped to test the relationship of SII with futile recanalization.

RESULTS

Among the 1,002 patients included, futile recanalization occurred in 508 (50.70%). No matter whether tested as quartiles or continuous variables, SII was significantly associated with futile recanalization (P < 0.05), and for every one standard deviation increase of SII, the risk of futile recanalization elevated by 22.3% (odds ratio 1.223, 95% confidence interval 1.053-1.444, P = 0.0093). Moreover, no significant interactions could be observed between SII or SII quartiles and age, baseline National Institutes of Health Stroke Scale scores, onset-to-recanalization time, and modified Thrombolysis in Cerebral Ischemia angiographic scores (all P for interaction > 0.05).

CONCLUSIONS

Early SII elevation was associated with an increased risk of futile recanalization among patients with EVT. Our results indicated that therapeutic drug targeting hyperreactive immune-inflammation response might be helpful for reducing the incidence of futile recanalization.

Safety and efficacy of adjunctive intra-arterial antithrombotic therapy during endovascular thrombectomy for acute ischemic stroke: a systematic review and meta-analysis

BACKGROUND

Half of patients who achieve successful recanalization following endovascular thrombectomy (EVT) for acute ischemic stroke experience poor functional outcome. We aim to investigate whether the use of adjunctive intra-arterial antithrombotic therapy (AAT) during EVT is safe and efficacious compared with standard therapy (ST) of EVT with or without prior intravenous thrombolysis.

METHODS

Electronic databases were searched (PubMed/MEDLINE, Embase, Cochrane Library) from 2010 until October 2023. Data were pooled using a random-effects model and reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Risk of bias was assessed using ROBINS-I and ROB-2. The primary outcome was functional independence (modified Rankin Scale (mRS) 0-2) at 3 months. Secondary outcomes were successful recanalization (modified Thrombolysis In Cerebral Infarction (TICI) 2b-3), symptomatic intracranial hemorrhage (sICH), and 90-day mortality.

RESULTS

41 randomized and non-randomized studies met the eligibility criteria. Overall, 15 316 patients were included; 3296 patients were treated with AAT during EVT and 12 020 were treated with ST alone. Compared with ST, patients treated with AAT demonstrated higher odds of functional independence (46.5% AAT vs 42.6% ST; OR 1.22, 95% CI 1.07 to 1.40, P=0.004, I2=48%) and a lower likelihood of 90-day mortality (OR 0.71, 95% CI 0.61 to 0.83, P<0.0001, I2=20%). The rates of sICH (OR 1.00, 95% CI 0.82 to 1.22,P=0.97, I2=13%) and successful recanalization (OR 1.09, 95% CI 0.84 to 1.42, P=0.52, I2=76%) were not significantly different.

CONCLUSION

The use of AAT during EVT may improve functional outcomes and reduce mortality rates compared with ST alone, without an increased risk of sICH. These findings should be interpreted with caution pending the results from ongoing phase III trials to establish the efficacy and safety of AAT during EVT.

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.

Mechanical thrombectomy with intra-arterial thrombolysis versus mechanical thrombectomy alone in patients with acute ischemic stroke: A systematic review and meta-analysis

BACKGROUND

There is conflicting evidence as to whether intra-arterial thrombolysis (IAT) adds benefit in patients with acute stroke who undergo mechanical thrombectomy (MT).

METHODS

We conducted a systematic review to identify studies that evaluate IAT in patients with acute stroke who undergo MT. Data were extracted from relevant studies found through a search of PubMed, Scopus, and Web of Science until February 2023. Statistical pooling with random effects meta-analysis was undertaken to evaluate odds of functional independence, mortality, and near-complete or complete angiographic recanalization with IAT compared to no IAT.

RESULTS

A total of 18 studies were included (3 matched, 14 unmatched, and 1 randomized). The odds ratio (OR) for functional independence (modified Rankin Scale: 0-2) at 90 days was 1.14 (95% confidence interval (CI): 0.95-1.37, p = 0.17, 16 studies involving 7572 patients) with IAT with moderate between-study heterogeneity (I2 = 38.1%). The OR for functional independence with IAT was 1.28 (95% CI: 0.92-1.78, p = 0.15) in studies that were either matched or randomized and 1.24 (95% CI: 0.97-1.58, p = 0.08) in studies with the highest quality score. IAT was associated with higher odds of near-complete or complete angiographic recanalization (OR: 1.65, 95% CI: 1.03-2.65, p = 0.04) in studies that were either matched or of randomized comparisons.

CONCLUSION

Although the odds of functional independence appeared to be higher with IAT and MT compared with MT alone, none of the results were statistically significant. A prominent effect of the design and quality of the studies was observed on the association between IAT and functional independence at 90 days.

Incidence, severity and impact on functional outcome of persistent hypoperfusion despite large-vessel recanalization, a potential marker of impaired microvascular reperfusion: Systematic review of the clinical literature

The reported incidence of persistent hypoperfusion despite complete recanalization as surrogate for impaired microvascular reperfusion (IMR) has varied widely among clinical studies, possibly due to differences in i) definition of complete recanalization, with only recent Thrombolysis in Cerebral Infarction (TICI) grading schemes allowing distinction between complete (TICI3) and partial recanalization with distal occlusions (TICI2c); ii) operational definition of IMR; and iii) consideration of potential alternative causes for hypoperfusion, notably carotid stenosis, re-occlusion and post-thrombectomy hemorrhage. We performed a systematic review to identify clinical studies that carried out brain perfusion imaging within 72 hrs post-thrombectomy for anterior circulation stroke and reported hypoperfusion rates separately for TICI3 and TICI2c grades. Authors were contacted if this data was missing. We identified eight eligible articles, altogether reporting 636 patients. The incidence of IMR after complete recanalization (i.e., TICI3) tended to decrease with the number of considered alternative causes of hypoperfusion: range 12.5-42.9%, 0-31.6% and 0-9.1% in articles that considered none, two or all three causes, respectively. No study reported the impact of IMR on functional outcome separately for TICI-3 patients. Based on this systematic review, IMR in true complete recanalization appears relatively rare, and reported incidence highly depends on definition used and consideration of confounding factors.

Uric Acid: A Translational Journey in Cerebroprotection That Spanned Preclinical and Human Data

Uric acid (UA) is a strong endogenous antioxidant that neutralizes the toxicity of peroxynitrite and other reactive species on the neurovascular unit generated during and after acute brain ischemia. The realization that a rapid reduction of UA levels during an acute ischemic stroke was associated with a worse stroke outcome paved the way to investigate the value of exogenous UA supplementation to counteract the progression of redox-mediated ischemic brain damage. The long translational journey for UA supplementation recently reached a critical milestone when the results of the multicenter NIH stroke preclinical assessment network (SPAN) were reported. In a novel preclinical paradigm, 6 treatment candidates including UA supplementation were selected and tested in 6 independent laboratories following predefined criteria and strict methodological rigor. UA supplementation was the only intervention in SPAN that exceeded the prespecified efficacy boundary with male and female animals, young mice, young rats, aging mice, obese mice, and spontaneously hypertensive rats. This unprecedented achievement will allow UA to undergo clinical testing in a pivotal clinical trial through a NIH StrokeNet thrombectomy endovascular platform created to assess new treatment strategies in patients treated with mechanical thrombectomy. UA is a particularly appealing adjuvant intervention for mechanical thrombectomy because it targets the microcirculatory hypoperfusion and oxidative stress that limits the efficacy of this therapy. This descriptive review aims to summarize the translational development of UA supplementation, highlighting those aspects that likely contributed to its success. It includes having a well-defined target and mechanism of action, and an approach that simultaneously integrated rigorous preclinical assessment, with epidemiologic and preliminary human intervention studies. Validation of the clinical value of UA supplementation in a pivotal trial would confirm the translational value of the SPAN paradigm in preclinical research.

Risk Factors, Pathophysiologic Mechanisms, and Potential Treatment Strategies of Futile Recanalization after Endovascular Therapy in Acute Ischemic Stroke

Endovascular therapy is the first-line treatment for acute ischemic stroke. However, studies have shown that, even with the timely opening of occluded blood vessels, nearly half of all patients treated with endovascular therapy for acute ischemic stroke still have poor functional recovery, a phenomenon called "futile recanalization.". The pathophysiology of futile recanalization is complex and may include tissue no-reflow (microcirculation reperfusion failure despite recanalization of the occluded large artery), early arterial reocclusion (reocclusion of the recanalized artery 24-48 hours post endovascular therapy), poor collateral circulation, hemorrhagic transformation (cerebral bleeding following primary ischemic stroke), impaired cerebrovascular autoregulation, and large hypoperfusion volume. Therapeutic strategies targeting these mechanisms have been attempted in preclinical research; however, translation to the bedside remains to be explored. This review summarizes the risk factors, pathophysiological mechanisms, and targeted therapy strategies of futile recanalization, focusing on the mechanisms and targeted therapy strategies of no-reflow to deepen the understanding of this phenomenon and provide new translational research ideas and potential intervention targets for improving the efficacy of endovascular therapy for acute ischemic stroke.

Microvascular reperfusion during endovascular therapy: the balance of supply and demand

BACKGROUND

Endovascular therapy (EVT) has revolutionized the treatment of acute stroke, but large vessel recanalization does not always result in tissue-level reperfusion. Cerebral blood flow (CBF) is not routinely monitored during EVT. We aimed to leverage diffuse correlation spectroscopy (DCS), a novel transcranial optical imaging technique, to assess the relationship between microvascular CBF and post-EVT outcomes.

METHODS

Frontal lobe CBF was monitored by DCS in 40 patients undergoing EVT. Baseline CBF deficit was calculated as the percentage of CBF impairment on pre-EVT CT perfusion. Microvascular reperfusion was calculated as the percentage increase in DCS-derived CBF that occurred with recanalization. The adequacy of reperfusion was defined by persistent CBF deficit, calculated as: baseline CBF deficit - microvascular reperfusion. A good functional outcome was defined as 90-day modified Rankin Scale score ≤2.

RESULTS

Thirty-six of 40 patients achieved successful recanalization, in whom microvascular reperfusion in itself was not associated with infarct volume or functional outcome. However, patients with good functional outcomes had a smaller persistent CBF deficit (median 1% (IQR -11%-16%)) than patients with poor outcomes (median 28% (IQR 2-50%)) (p=0.02). Smaller persistent CBF deficit was also associated with smaller infarct volume (p=0.004). Multivariate models confirmed that persistent CBF deficit was independently associated with infarct volume and functional outcome.

CONCLUSIONS

CBF augmentation alone does not predict post-EVT outcomes, but when microvascular reperfusion closely matches the baseline CBF deficit, patients experience favorable clinical and radiographic outcomes. By recognizing inadequate reperfusion, bedside CBF monitoring may provide opportunities to personalize post-EVT care aimed at CBF optimization.

Intra-Arterial Thrombolysis is Associated with Delayed Reperfusion of Remaining Vessel Occlusions following Incomplete Thrombectomy

BACKGROUND AND PURPOSE

Intra-arterial thrombolytics may be used to treat distal vessel occlusions, which cause incomplete reperfusion following mechanical thrombectomy. Because immediate reperfusion after intra-arterial thrombolytics occurs rarely, the aim of this study was to assess the delayed effect of intra-arterial thrombolytics using follow-up perfusion imaging.

MATERIALS AND METHODS

We included patients from a prospective stroke registry (February 2015 to September 2022) who had undergone mechanical thrombectomy and had incomplete reperfusion (expanded TICI 2a-2c) and available 24 hour perfusion imaging. Perfusion imaging was rated as delayed reperfusion if time-sensitive perfusion maps did not show wedge-shaped delays suggestive of persisting occlusions corresponding to the post-mechanical thrombectomy angiographic deficit. Patients treated with intra-arterial thrombolytics were compared with controls using multivariable logistic regression and inverse probability of treatment weighting matching for baseline differences and factors associated with delayed reperfusion.

RESULTS

The median age of the final study population (n = 459) was 74 years (interquartile range, 63-81 years), and delayed reperfusion occurred in 61% of cases. Patients treated with additional intra-arterial thrombolytics (n = 40) were younger and had worse expanded TICI scores. After matching was performed, intra-arterial thrombolytics was associated with higher rates of delayed reperfusion (adjusted OR = 2.7; 95% CI, 1.1-6.4) and lower rates of new infarction in the residually hypoperfused territory after mechanical thrombectomy (adjusted OR = 0.3; 95% CI, 0.1-0.7). No difference was found in the rates of functional independence (90-day mRS, 0-2; adjusted OR = 1.4; 95% CI, 0.4-4.1).

CONCLUSIONS

Rescue intra-arterial thrombolytics is associated with delayed reperfusion of remaining vessel occlusions following incomplete mechanical thrombectomy. The value of intra-arterial thrombolytics as a potential therapy for incomplete reperfusions after mechanical thrombectomy should be assessed in the setting of randomized controlled trials.

Effect of intra-arterial thrombolysis following successful endovascular thrombectomy on functional outcomes in patients with large vessel occlusion acute ischemic stroke: A post-CHOICE meta-analysis

INTRODUCTION

Endovascular thrombectomy (EVT) is the standard treatment of acute ischemic stroke (AIS) due to large vessel occlusion (LVO). Although > 70% of patients in the trials assessing EVT for AIS-LVO had successful recanalization, only a third ultimately achieved favorable outcomes. A "no-reflow" phenomenon due to distal microcirculation disruption might contribute to such suboptimal outcomes. Combining intra-arterial (IA) tissue plasminogen activator (tPA) and EVT to reduce the distal microthrombi burden was investigated in a few studies. We present a pooled-data meta-analysis of the existing evidence of this combinatorial treatment.

METHODS

We followed the Preferred Reporting Items for Systematic Review and Meta-analyses (PRISMA) recommendations. We aimed to include all original studies investigating EVT plus IA tPA in AIS-LVO patients. Using R software, we calculated pooled odds ratios (ORs) with corresponding 95% confidence intervals (CI). A fixed-effects model was adopted to evaluate pooled data.

RESULTS

Five studies satisfied the inclusion criteria. Successful recanalization was comparable between the IA tPA and control groups at 82.9% and 82.32% respectively. The 90-day functional independence was similar between both groups (OR= 1.25; 95% CI= 0.92-1.70; P= 0.154). Symptomatic intracranial hemorrhage (sICH) was also comparable between both groups (OR= 0.66; 95% CI= 0.34-1.26; P= 0.304).

CONCLUSION

Our current meta-analysis does not show significant differences between EVT alone and EVT plus IA tPA in terms of functional independence or sICH. However, with the limited number of studies and included patients, more randomized controlled trials (RCTs) are needed to further investigate the benefits and safety of combined EVT and IA tPA.

Endovascular Thrombectomy for Anterior Circulation Large Vessel Occlusion Stroke: An Evolution of Trials

The last decade's progress in demonstrating the clinical benefit of endovascular thrombectomy (EVT) in patients with large vessel occlusion stroke has transformed the paradigm of care for these patients. This review presents the milestones in implementing EVT as standard of care, demonstrates the current state of evidence, provides guidance for identifying the candidate patient for EVT, and highlights unsolved and controversial issues. Ongoing trials investigate broadening of EVT indications for patients who present with large core infarction, adjunctive intra-arterial thrombolysis, medium vessel occlusion, low NIHSS, and tandem occlusion.