Autopsy findings after intracranial thrombectomy for acute ischemic stroke: a clinicopathologic study of 5 patients

Thrombectomy Outcomes in Acute Basilar Artery Occlusions Due to Intracranial Atherosclerotic Disease

BACKGROUND AND OBJECTIVES

Intracranial atherosclerotic disease (ICAD) large vessel occlusion (LVO) is responsible for up to 30% of LVO. In this study, we aimed to determine the likelihood of favorable functional outcomes (modified Rankin Scale 0-3) in acute ICAD-LVO basilar occlusion compared with embolic basilar occlusion.

METHODS

This is an analysis of the Posterior Circulation Ischemic Stroke Evaluation: Analyzing Radiographic and Intraprocedural Predictors for Mechanical Thrombectomy Registry in which patients with acute basilar artery occlusions from 8 comprehensive stroke centers were included from 2015 to 2021. Patients were dichotomized into with (ICAD-LVO) or without underlying ICAD (embolic). Descriptive statistics for each group and multivariate logistic analysis were performed on the primary outcome.

RESULTS

Three hundred forty-six patients were included. There were 215 patients with embolic (62%) and 131 patients with ICAD-LVO (38%). Baseline demographics were equivalent between the 2 groups except for sex (male 47% vs 67%; P < .001), history of stroke (12% vs 25%; P = .002), and atrial fibrillation (31% vs 17%; P = .003). At 90 days, patients in the ICAD-LVO cohort were less likely to achieve favorable functional outcomes (odds ratio [OR] 0.41, 95% CI 0.22-0.72; P = .003) after adjusting for potentially confounding factors. In addition, ICAD-LVO strokes were less likely to achieve thrombolysis in cerebral infarction ≥2b (OR 0.29, 95% CI 0.14-0.57; P < .001). ICAD-LVO lesions were more likely to require stent placement (OR 14.94, 95% CI 4.91-45.49; P < .001). Subgroup analysis demonstrated favorable functional outcomes in patients who underwent stenting and angioplasty compared with failed recanalization cohort (OR 4.96, 95% CI 1.68-14.64; P < .004).

CONCLUSION

Patients with acute basilar ICAD-LVO have higher morbidity and mortality compared with patients with embolic source. Lower rates of successful recanalization in the ICAD-LVO cohort support this finding. Our subgroup analysis demonstrates that stenting should be considered in patients with recanalization failure. Rates of symptomatic intracranial hemorrhage were similar between the ICAD-LVO and embolic cohorts.

Determining the safety of the tobacco cembranoid (1S,2E,4R,6R,7E,11E)-Cembratriene-4,6-diol (4R): A translational study in nonhuman primates

The tobacco cembranoid known as (1S,2E,4R,6R,7E,11E)-2,7,11-cembratriene-4,6-diol (4R) has been shown to offer neuroprotection against conditions such as brain ischemia, systemic inflammation, Parkinson's disease, and organophosphate toxicity in rodents. Previous safety studies conducted on male and female Sprague Dawley rats revealed no significant side effects following a single injection of 4R at varying concentrations (6, 24, or 98 mg/kg of body weight). This study aimed to assess the potential of 4R for clinical trials in neurotherapy in male nonhuman primates. Ten macaques (Macacca mulatta) were randomly separated into two groups of 5 and then intravenously injected with 4R or vehicle for 11 consecutive days at a dose of 1.4 mg/kg. Throughout the study, we monitored brain activity by electroencephalogram, somatosensory evoked potentials, and transcranial motor evoked potentials on days 0, 4, 8, and 12 and found no significant changes. The spontaneous behavior of the primates remained unaffected by the treatment. Minor hematological and blood composition variations were also detected in the experimental animals but lacked clinical significance. In conclusion, our results reinforce the notion that 4R is non-toxic in nonhuman primates under the conditions of this study.

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.

Intracranial atherosclerotic disease: current management strategies

A stroke due to underlying intracranial large artery occlusion, which is atherosclerotic in nature, is known as intracranial atherosclerotic disease (ICAD). It is important to recognize that ischaemic stroke due to ICAD differs from extracranial disease and other stroke aetiologies and requires a nuanced approach. It is a significant cause of stroke worldwide, and severe symptomatic ICAD can present challenges from a therapeutic standpoint, including recurrent ischaemic stroke despite optimal management. Furthermore, exploring the underlying pathophysiological mechanisms responsible for the disease may be necessary while considering treatment options. This narrative review aims to provide an all-encompassing overview of this disease. Epidemiology and clinical pathophysiology will be explored in detail. The findings of large clinical trials will serve as a guide to finding the most optimized management strategies. Another critical question that arises is the treatment of acute ischaemic stroke due to large vessel occlusion with underlying intracranial atherosclerosis, is the treatment and clinical diagnosis the same as for other aetiologies of stroke (i.e. extracranial disease and nonvalvular atrial fibrillation)? Consequently, secondary prevention of patients with ischaemic stroke or transient ischaemic attack will be divided into medical therapy, risk factor control, and endovascular and surgical treatment options.

Characteristics of intracranial plaque in patients with non-cardioembolic stroke and intracranial large vessel occlusion

OBJECTIVE

To determine the characteristics of intracranial plaque proximal to large vessel occlusion (LVO) in stroke patients without major-risk cardioembolic source using 3.0 T high-resolution MRI (HR-MRI).

METHODS

We retrospectively enrolled eligible patients from January 2015 to July 2021. The multidimensional parameters of plaque such as remodelling index (RI), plaque burden (PB), percentage lipid-rich necrotic core (%LRNC), presence of discontinuity of plaque surface (DPS), fibrous cap rupture, intraplaque haemorrhage and complicated plaque were evaluated by HR-MRI.

RESULTS

Among 279 stroke patients, intracranial plaque proximal to LVO was more prevalent in the ipsilateral versus contralateral side to stroke (75.6% vs 58.8%, p<0.001). The larger PB (p<0.001), RI (p<0.001) and %LRNC (p=0.001), the higher prevalence of DPS (61.1% vs 50.6%, p=0.041) and complicated plaque (63.0% vs 50.6%, p=0.016) were observed in the plaque ipsilateral versus contralateral to stroke. Logistic analysis showed that RI and PB were positively associated with an ischaemic stroke (RI: crude OR: 1.303, 95% CI 1.072 to 1.584, p=0.008; PB: crude OR: 1.677, 95% CI 1.381 to 2.037, p<0.001). In subgroup with <50% stenotic plaque, the greater PB, RI, %LRNC and the presence of complicated plaque were more closely related to stroke, which was not evident in subgroup with ≥50% stenotic plaque.

CONCLUSION

This is the first study to report the characteristics of intracranial plaque proximal to LVO in non-cardioembolic stroke. It provides potential evidence to support different aetiological roles of <50% stenotic vs ≥50% stenotic intracranial plaque in this population.

Multiple large vessel occlusions resulting in vessel perforation in single pass of mechanical thrombectomy with stent retriever

Mechanical thrombectomy (MT) is a highly effective treatment for acute ischemic stroke, and hemorrhagic complications caused by vessel injury are rare. However, there is no evidence regarding the efficacy of MT for multiple large vessel occlusion or its procedural strategy. Herein, we report a case of MT with a stent retriever for multiple large vessel occlusion in the internal carotid artery and middle cerebral artery M1 distal, which resulted in vessel perforation in a single pass. A 79-year-old woman underwent MT for internal carotid artery occlusion, and multiple large vessel occlusion was observed on digital subtraction angiography. A longer and larger stent retriever was selected for thrombus retrieval in a single pass. Immediately after retrieval, digital subtraction angiography revealed internal carotid artery recanalization. Then, extravasation was observed from the M1 distal occlusion. Treatment was interrupted after hemostasis was confirmed. Nevertheless, rebleeding occurred after 4 hours. Emergency trapping was performed, and vessel perforation of >1 mm was observed. When retrieving a thrombus in a single pass with a stent retriever for multiple large vessel occlusion, vessel perforation may occur if the device is selected according to the diameter of the proximal occluded vessel. Based on the type of device, even a single pass may result in vessel perforation. Although aggressive MT intervention should be performed for multiple large vessel occlusion, a device that is appropriate for the pathological condition must be selected.

Underlying intracranial atherosclerotic disease is associated with worse outcomes in acute large vessel occlusion undergoing endovascular thrombectomy

BACKGROUND

Data on large vessel occlusion (LVO) management due to intracranial atherosclerotic disease (ICAD) are scarce.

OBJECTIVE

To compare clinical outcomes between patients with ICAD and those without ICAD following mechanical thrombectomy (MT).

METHODS

We performed a retrospective analysis of consecutive patients who underwent MT for LVO in a large academic comprehensive stroke center, and compared in-hospital mortality, 90-day mortality, favorable functional outcome at 90 days, and symptomatic intracranial hemorrhage (ICH) using chi-squared tests and multivariate logistic regression analyses. We defined ICAD as observable plaque at occlusion site post-thrombectomy.

RESULTS

Among 215 patients (mean age 67.1 ± 16.0 years; 60.5% female; 83.6% Black, median NIHSS score 16), ICAD was present in 38 patients (17.7%). Diabetes and dyslipidemia were more common in those with ICAD (57.9% vs. 38.4%, p = 0.027 and 29.0% vs. 14.7%, p = 0.035, respectively). Substantial reperfusion (TICI ≥2b) was achieved less often (84.2% vs. 94.4%, p = 0.031) but symptomatic ICH was also less common in ICAD patients (0% vs. 9.0%, p = 0.081). In-hospital and 90-day mortality were more common (36.8% vs. 15.8%, p = 0.003 and 52.6% vs. 26.6%, p = 0.002, respectively) and favorable functional outcome (mRS 0-2) at 90 days was less common (7.9% vs. 33.9%, p = 0.001) in ICAD patients. After adjusting for prognostic variables, ICAD was independently associated with in-hospital mortality (OR=4.1, 95% CI 1.7-9.7), 90-day mortality (OR=3.7, 95% CI 1.6-8.6), and poor functional outcome at 90 days (OR=5.5, 95% CI 1.6-19.4).

CONCLUSION

Symptomatic ICAD in a predominantly African American cohort is associated with increased odds of mortality and poor functional outcome at 90 days in patients with LVO undergoing MT.

Large Vessel Occlusion Stroke due to Intracranial Atherosclerotic Disease: Identification, Medical and Interventional Treatment, and Outcomes

Large vessel occlusion stroke due to underlying intracranial atherosclerotic disease (ICAD-LVO) is prevalent in 10 to 30% of LVOs depending on patient factors such as vascular risk factors, race and ethnicity, and age. Patients with ICAD-LVO derive similar functional outcome benefit from endovascular thrombectomy as other mechanisms of LVO, but up to half of ICAD-LVO patients reocclude after revascularization. Therefore, early identification and treatment planning for ICAD-LVO are important given the unique considerations before, during, and after endovascular thrombectomy. In this review of ICAD-LVO, we propose a multistep approach to ICAD-LVO identification, pretreatment and endovascular thrombectomy considerations, adjunctive medications, and medical management. There have been no large-scale randomized controlled trials dedicated to studying ICAD-LVO, therefore this review focuses on observational studies.

Increased Number of Passes and Double Stent Retriever Technique Induces Cumulative Injury on Arterial Wall After Mechanical Thrombectomy in a Swine Model

The number of stentriever passes during endovascular thrombectomy impacts clinical outcomes in acute ischemic stroke. Previous studies suggest that the simultaneous double stent retriever technique (DSRT) could improve the efficacy and reduce the number of passes. We aim to analyze the degree of vessel wall injury according to the number of passes and technique (single vs. simultaneous devices). Histological changes were evaluated in renal arteries (RAs) of swine models after thrombectomy (1, 2, or 3 passes) with single stent (SSRT) and DSRT. Thrombectomy passes were performed in 12 RA: 3 samples from each artery were studied by optical microscopy to assess a vascular damage score. All thirty-six samples showed endothelial denudation and different degrees of damage in the deepest layers of the arterial wall; however, all arteries remained patent by the time of assessment. In all cases, the degree of vascular injury increased with the number of passes. Compared with a SSRT, DSRT showed a higher severity of histological damage corresponding to the damage caused by 1.4 SSRT passes. However, in distal arteries, vascular damage was relatively similar when comparing SSRT with multiple passes and DSRT with one pass. The degree of vessel injury increases with the number of passes. Even though histological damage per pass was 1.4 higher with DSRT than SSRT, short-term vessel patency was not compromised after up to 3 DSRT passes. Further studies are needed to characterize the risk-benefit ratio of the DSRT in routine clinical practice.

Rescue Endovascular Treatment for Emergent Large Vessel Occlusion With Underlying Intracranial Atherosclerosis: Current State and Future Directions

Intracranial atherosclerosis (ICAS) is one of the most common causes of stroke worldwide and is associated with high risk of stroke recurrence. While the most common clinical presentation is acute–subacute transient ischemic attack or ischemic stroke, occasionally, patients with underlying ICAS present with acute occlusion of the affected vessel. Diagnosis and endovascular management of ICAS-related emergent large vessel occlusion (ELVO) can be challenging. Herein, we review the current evidence supporting endovascular management of ICAS-related ELVO and discuss future directions.

[Nonrecanalization after mechanical thrombectomy in acute ischemic stroke due to infective endocarditis: an autopsy case]

An 86-year-old man was admitted for the abrupt onset of right hemiparesis and aphasia. DWI revealed the high intensity legion in the left insular cortex, and MRA demonstrated the left middle cerebral artery occlusion. Recanalization of the artery was not achieved after mechanical thrombectomy. The diagnosis of infective endocarditis was made as Enterococcus faecalis was cultured from the blood, and mobile vegetation was detected at the aortic valve by transthoracic echocardiography. The patient died from multiple organ failure at 19 days. Autopsy findings revealed fibrin-rich thrombus in the left middle cerebral artery containing neutrophils and bacteria. At the occluded site, neutrophils had intensively infiltrated into the vessel wall, and endothelial cells had partially disappeared. Moreover, disrupted internal elastic lamina was discovered. These findings could indicate that the thrombus had adhered to the vessel wall. The adhesion of the thrombus and vessel wall could be associated with unsuccessful recanalization after endovascular thrombectomy in patients with ischemic stroke due to infective endocarditis.

Outcomes of Rescue Endovascular Treatment of Emergent Large Vessel Occlusion in Patients With Underlying Intracranial Atherosclerosis: Insights From STAR

Background

Some emergent large vessel occlusions (ELVOs) are refractory to reperfusion because of underlying intracranial atherosclerosis (ICAS), often requiring rescue therapy (RT) with balloon angioplasty, stenting, or both. In this study, we investigate the safety, efficacy, and long‐term outcomes of RT in the setting of mechanical thrombectomy for ICAS‐related ELVO.

Methods and Results

We queried the databases of 10 thrombectomy‐capable centers in North America and Europe included in STAR (Stroke Thrombectomy and Aneurysm Registry). Patients with ELVO who underwent ICAS‐related RT were included. A matched sample was produced for variables of age, admission National Institute of Health Stroke Scale, Alberta Stroke Program Early CT Score, onset to groin puncture time, occlusion site, and final recanalization. Out of 3025 patients with MT, 182 (6%) patients required RT because of underlying ICAS. Balloon angioplasty was performed on 122 patients, and 117 patients had intracranial stenting. In the matched analysis, 141 patients who received RT matched to a similar number of controls. The number of thrombectomy passes was higher (3 versus 1, P<0.001), and procedural time was longer in the RT group (52 minutes versus 36 minutes, P=0.004). There was a higher rate of symptomatic hemorrhagic transformation in the RT group (7.8% versus 4.3%, P=0.211), however, the difference was not significant. There was no difference in 90‐day modified Rankin scale of 0 to 2 (44% versus 47.5%, P=0.543) between patients in the RT and control groups.

Conclusions

In patients with ELVO with underlying ICAS requiring RT, despite longer procedure time and a more thrombectomy passes, the 90 days favorable outcomes were comparable with patients with embolic ELVO.

High-resolution vessel wall imaging after mechanical thrombectomy

OBJECTIVES

High-resolution magnetic resonance imaging has the potential of characterising arterial wall changes after endovascular mechanical thrombectomy. The purpose of this study is to evaluate high-resolution magnetic resonance imaging features of large intracranial arteries following mechanical thrombectomy.

METHODS

Patients who presented with acute ischaemic stroke due to large vessel occlusion and underwent mechanical thrombectomy were prospectively recruited. Subjects underwent high-resolution magnetic resonance imaging within 24 hours of the procedure. Magnetic resonance imaging sequences included whole brain T1 pre and post-contrast black-blood imaging, three-dimensional T2, contrast-enhanced magnetic resonance angiography and susceptibility-weighted imaging. Arterial wall enhancement was objectively assessed after normalisation with the pituitary stalk. The contrast ratio of target vessels was compared with non-affected reference vessels.

RESULTS

Twenty patients with 22 target vessels and 20 reference vessels were included in the study. Sixteen patients were treated with stentriever with or without aspiration, and four with contact aspiration only. Significantly higher arterial wall enhancement was identified on the target vessel when compared to the reference vessel (U = 22.5, P < 0.01). The stentriever group had an 82% increase in the contrast ratio of the target vessel (x̄ = 0.75 ± 0.21) when compared to the reference vessel (x̄ = 0.41 ± 0.13), whereas the contact aspiration group had a 64% increase of the contrast ratio difference between target (x̄ = 0.62 ± 0.07) and reference vessels (x̄ = 0.38 ± 0.12). Approximately 65% of patients in the stentriever group had a positive parenchymal susceptibility-weighted imaging versus 25% in the contact aspiration group. There was no statistically significant correlation between susceptibility-weighted imaging volume and the percentage increase in the contrast ratio (r_s = 0.098, P = 0.748).

CONCLUSIONS

This prospective pilot study used the objective quantification of arterial wall enhancement in determining arterial changes after mechanical thrombectomy. Preliminary data suggest that the use of stentrievers is associated with a higher enhancement as compared to reperfusion catheters.

The Protective Effects of Statins Towards Vessel Wall Injury Caused by a Stent Retrieving Mechanical Thrombectomy Device : A Histological Analysis of the Rabbit Carotid Artery Model

Objective

Endovascular mechanical thrombectomy (MT) has been regarded as one of the standard treatments for acute ischemic stroke caused by large vessel occlusion. Despite the wide use of stent retrievers for MT, arterial intimal damage caused when deployed stent is pulled has been a certain disadvantage. We hypothesized that statin could protect and stabilize vessel damage after endovascular MT using a stent retriever. In this animal study, we observed the protective effects of the statins towards MT-induced vessel wall injury.

Methods

Twenty-eight carotid arteries of fourteen rabbits were used in the experiments with MT using stent retriever. We divided the rabbits into four groups as follows : group 1, negative control; group 2, positive control; group 3, statin before MT; and group 4, statin after MT. After MT procedures, we harvested the carotid arteries and performed histomorphological and immunohistochemical analyses.

Results

In histomorphological analysis with hematoxylin and eosin and Masson's trichrome stain, significant intimal thickening (p<0.05) was observed in the positive control (group 2), compared to in the negative control (group 1). Intimal thickening was improved in the statin-administered groups (groups 3 and 4 vs. group 2, p<0.05). We also observed that statin administration after MT (group 4) resulted in a more effective decrease in intimal thickness than statin administration before MT (group 3) (p<0.05). We performed immunohistochemical analysis with the antibodies for tumor necrosis factor-alpha (TNF-α), cluster of differentiation (CD)11b, and CD163. In contrast to the negative control (group 1), the stained percentage areas of all immunological markers were markedly increased in the positive control (group 2) (p<0.05). Based on statin administration, the percentage area of TNF-α staining was significantly reduced (p<0.05) in group 3, compared to the positive control group (group 2). However, significant differences were not observed for CD11b and CD163 staining. In group 4, no significant differences were observed for TNF-α, CD11b, and CD163 staining (p≥0.05). The differences in the percentage areas of the different markers between the statin-administered groups (groups 3 and 4) were also not revealed.

Conclusion

We presented that statin administration before and after MT exerted protective effects towards vessel wall injury. The efficacy of statins was greater post-administration than pre-administration. Thus, statin administration in routine prescriptions in the peri-procedural period is strongly advised.

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.

Immediate effects of first-line thrombectomy devices for intracranial atherosclerosis-related occlusion: stent retriever versus contact aspiration

BACKGROUND

Although stent retriever (SR) is recommended as a frontline device of endovascular treatment (EVT) for embolic large artery occlusion causing acute ischemic stroke, contact aspiration (CA) device showed similar efficacy in the recent trials. However, the efficacy of the both devices as first-line therapy for intracranial atherosclerotic stenosis (ICAS)-related large vessel occlusion has not yet been established. Therefore, we compared the immediate effects and final outcomes of SR and CA as first-line devices for treating ICAS-related occlusions.

METHODS

We retrospectively analyzed the data of patients who underwent EVT for acute ischemic stroke from the registry of three Korean hospitals. Patients with ICAS-related occlusion who were treated within 24 h of onset of the symptoms were included. We investigated immediate reperfusion performance, immediate safety outcomes, and 3-month clinical outcomes for the two first-line devices.

RESULTS

Of the 720 registered patients, 111 were eligible for this study. Forty-nine patients (44.1%) used SR and 62 (55.9%) used CA as the first-line device. Achieving successful reperfusion immediately after first-line thrombectomy was more frequent in the SR group than that in the CA group (77.6% vs. 43.5%, p = 0.001), with fewer additional rescue treatments (12.2% vs. 59.7%, p < 0.001). The incidence of iatrogenic dissection or rupture was lower in the SR group than that in the CA group (8.2% vs. 29.0%, p = 0.012). After additional rescue treatments, however, the final successful reperfusion rate did not differ between the two groups (SR 87.8% vs. CA 77.4%, p = 0.247), and there was no significant difference in the 3-month good outcomes (modified Rankin Scale, p = 0.524).

CONCLUSIONS

First-line SR thrombectomy showed higher immediate reperfusion and less vessel injury for ICAS-related occlusions than CA. However, there was no significant difference in the final reperfusion status or 3-month outcomes from additional rescue treatments.

Delayed Vasospasm Associated with Mechanical Thrombectomy for Acute Ischemic Stroke

Vasospasm related to mechanical thrombectomy for acute ischemic stroke sometimes occurs as a periprocedural complication, although it is usually a transient and asymptomatic event. Herein we describe the second case of symptomatic delayed vasospasm associated with mechanical thrombectomy, highlighting its unique device-related adverse event. When intraoperative vasospasm occurs, we should pay attention to this phenomenon, and close follow-up is necessary.

Optical coherence tomography imaging after endovascular thrombectomy: a novel method for evaluating vascular injury in a swine model

OBJECTIVE

Although studies have shown that some degree of iatrogenic endothelial injury occurs during endovascular thrombectomy (EVT), the clinical significance of such injury is uncertain. Furthermore, it is likely that iatrogenic effects such as endothelial denudation, intimal dissection, and tunica media edema will have varying clinical implications. The purpose of this study was to assess the feasibility of endovascular optical coherence tomography (OCT) in quantifying vessel injury in real time after EVT, correlate vessel injury with histological findings, and perform imaging at varying time intervals after EVT to assess the impact of prolonged direct exposure of the vessel to the thrombus.

METHODS

Yorkshire swine weighing 35-40 kg were selected for use as the animal model, with a total of 9 vessels from 3 swine examined. Thrombectomy was performed using a second-generation stent retriever 1, 3, and 6 hours after thrombus deposition. The presence and degree of denudation of the endothelium, detachment and separation of the layers of the tunic media, hemorrhage within the media, dissection of the vessels, and thrombus within the lumina were assessed using OCT images acquired immediately after EVT. Bland-Altman analysis indicated that these OCT findings were correlated with postmortem histological findings.

RESULTS

OCT image acquisition was technically successful in all cases. Endothelial denudation was present in 65% ± 16%, 87% ± 8%, and 93% ± 7% of the vessel surface 1, 3, and 6 hours, respectively, after thrombus deposition and subsequent EVT. Residual intraluminal thrombus was present in vessels at all time intervals despite complete angiographic revascularization. Bland-Altman plots showed good agreement between OCT and histological analysis with respect to the degree of endothelial denudation and elevation, separation of the tunica media, and hemorrhage within the media. OCT appears to be more specific than histological analysis in detecting endothelial elevation.

CONCLUSIONS

OCT is a feasible method that can be used to assess vascular injury after EVT with histological accuracy. Varying degrees of vessel injury occur after EVT, and residual luminal thrombus can be present despite complete angiographic revascularization.

Pathological Safety Assessment in Preclinical Neurothrombectomy Studies

The design, production, and preclinical testing of neurothrombectomy devices is in a burgeoning phase as the demand escalates for safe and reliable treatment options following neurovascular stroke. Currently, there is a paucity of published data describing the development of iatrogenic vascular lesions occurring secondary to neurothrombectomy procedures. In an effort to test new devices, demonstrate device safety, satisfy regulatory requirements, and develop an understanding of the potential for associated vascular pathology, investigators are establishing appropriate methodology in suitable animal models. Significant challenges exist in identifying a single animal species that can be consistently utilized in all phases of device development. These aforementioned challenges are underscored by the intricacies of neurovascular pathology, thrombovascular interactions, and vascular responses to injury.

Ox-LDL induces endothelial cell apoptosis and macrophage migration by regulating caveolin-1 phosphorylation

Oxidative low-density lipoprotein (ox-LDL) is a risk factor for atherosclerosis. Ox-LDL leads to endothelial injury in the initial stage of atherosclerosis. In this study, we investigated the role of ox-LDL in endothelial injury and macrophage recruitment. We demonstrated that ox-LDL promoted a dose-dependent phosphorylation of caveolin-1 in human umbilical vein endothelial cells. Phosphorylated caveolin-1 increased ox-LDL uptake. Intracellular accumulation of ox-LDL induced NF-κB p65 phosphorylation, promoted HMGB1 translocation from nucleus to cytoplasm and cytochrome C release from mitochondria to cytoplasm, and activated caspase 3, resulting in cell apoptosis. NF-κB activation also facilitated cavolin-1 phosphorylation and HMGB1 expression. In addition, caveolin-1 phosphorylation favored HMGB1 release and nuclear translocation of EGR1. Nuclear translocation of EGR1 contributed to cytoplasmic translocation of HMGB1. The extracellular HMGB1 induced the migration of PMBC-derived macrophages toward HUVECs in a TLR4-dependent manner. Our results suggested that ox-LDL promoted HUVECs apoptosis and macrophage recruitment by regulating caveolin-1 phosphorylation.

Contrast Extravasation versus Hemorrhage after Thrombectomy in Patients with Acute Stroke

BACKGROUND AND PURPOSE

Intra-arterial recanalization postprocedural imaging in stroke patients can result in diagnostic complications due to hyperdensities on noncontrast computed tomography (CT), which may represent either contrast extravasation or intracranial hemorrhage. If these lesions are hemorrhage, then they are risk factors becoming symptomatic, which, if not distinguished, can alter clinical management. We investigate the effects of iodinated contrast on postprocedural magnetic resonance imaging (MRI) and prevalence of equivocal imaging interpretations of postprocedural extravasated contrast versus hemorrhage while identifying protocol pitfalls.

METHODS

We identified 10 patients diagnosed with ischemic stroke who underwent intra-arterial recanalization in a 5-year period. These patients demonstrated a hyperdensity on a postprocedural CT within 24 hours, underwent an MRI within 48 hours, and an additional confirmatory noncontrast CT at least 72 hours postprocedure.

RESULTS

Postprocedural MRI in all 10 stroke patients demonstrated T1 - and T2 -relaxation time changes due to residual iodine contrast agents. This lead to false positive postprocedural hemorrhage MRI interpretations in 2/10 patients, 3/10 false negative interpretations of contrast extravasation, and 5/10 equivocal interpretations suggesting extravasation or hemorrhage. Of these five cases, two were performed with gadolinium.

CONCLUSION

MRI done within 48 hours postprocedure can lead to false positive hemorrhage or false negative contrast extravasation interpretations in stroke patients possibly due to effects from the administered angiographic contrast. Additionally, MRI should be done both after 72 hours for confirmation and without gadolinium contrast as the effects of the gadolinium contrast and residual angiographic contrast could lead to misdiagnosis.

Vessel Wall Enhancement and Blood–Cerebrospinal Fluid Barrier Disruption After Mechanical Thrombectomy in Acute Ischemic Stroke

Background and Purpose—

Less than half of acute ischemic stroke patients treated with mechanical thrombectomy obtain permanent clinical benefits. Consequently, there is an urgent need to identify mechanisms implicated in the limited efficacy of early reperfusion. We evaluated the predictors and prognostic significance of vessel wall permeability impairment and its association with blood–cerebrospinal fluid barrier (BCSFB) disruption after acute stroke treated with thrombectomy.

Methods—

A prospective cohort of acute stroke patients treated with stent retrievers was analyzed. Vessel wall permeability impairment was identified as gadolinium vessel wall enhancement (GVE) in a 24- to 48-hour follow-up contrast-enhanced magnetic resonance imaging, and severe BCSFB disruption was defined as subarachnoid hemorrhage or gadolinium sulcal enhancement (present across >10 slices). Infarct volume was evaluated in follow-up magnetic resonance imaging, and clinical outcome was evaluated with the modified Rankin Scale at day 90.

Results—

A total of 60 patients (median National Institutes of Health Stroke Scale score, 18) were analyzed, of whom 28 (47%) received intravenous alteplase before mechanical thrombectomy. Overall, 34 (57%) patients had GVE and 27 (45%) had severe BCSFB disruption. GVE was significantly associated with alteplase use before thrombectomy and with more stent retriever passes, along with the presence of severe BCSFB disruption. GVE was associated with poor clinical outcome, and both GVE and severe BCSFB disruption were associated with increased final infarct volume.

Conclusions—

These findings may support the clinical relevance of direct vessel damage and BCSFB disruption after acute stroke and reinforce the need for further improvements in reperfusion strategies. Further validation in larger cohorts of patients is warranted.

Histological examination of vascular damage caused by stent retriever thrombectomy devices

Background and objectives

Although the recently marketed stent retriever thrombectomy devices have demonstrated a high recanalization rate and favorable clinical outcomes, there is a concern about the risks of intimal injuries when pulling out the stent in the unfolded position. In this study, the Solitaire Flow Restoration System and the Trevo retriever were used in a histopathological comparison of vascular injuries caused by stent retriever thrombectomy devices.

Methods

Rabbit carotid arteries were used in the experiments with stent retriever thrombectomy devices. Carotid artery samples were harvested either 1 or 2 weeks postoperatively for histological examination.

Results

Histological changes caused by the use of stent retriever thrombectomy devices were observed from the intimal to medial layers. With the Solitaire FR 4 mm, intimal and medial thickening was observed 1 week postoperatively, and progression of intimal thickening was observed 2 weeks postoperatively. The extent of intimal thickening tended to be greater with the Solitaire FR 6 mm than with the Solitaire FR 4 mm, but this difference was not significant. Compared with the Solitaire FR 4 mm, the Trevo had a significantly smaller area of intimal thickening.

Conclusions

Although there are some differences among devices, results from this study indicate that stent retriever thrombectomy devices induce vascular damage that extends to the medial layer.

Correlation of clot imaging with endovascular recanalization in internal carotid artery terminus occlusion

BACKGROUND AND PURPOSE

In a swine stroke model we have previously demonstrated a high-intensity fluid attenuated inversion recovery (FLAIR) signal representing the erythrocyte component of the clot. We hypothesized that the intensity of the FLAIR clot signal in patients with acute stroke may predict the efficacy of recanalization by thrombectomy devices. In this study we compared the pretreatment FLAIR signal intensity of the clots in the distal internal carotid artery (ICA) and the degree of angiographic recanalization rate after mechanical thrombectomy.

METHODS

25 consecutive acute stroke patients with ICA terminus (ICA-T) occlusion diagnosed with MRI at the UCLA Medical Center between 2002 and 2013 were retrospectively reviewed. The intensity of the FLAIR clot signal at the distal ICA was blindly compared with the angiographic recanalization status (successful recanalization defined as Thrombolysis In Cerebral Infarction (TICI) score of 2b-3) and non-successful recanalization as TICI score 0-2a) after endovascular treatment. Multivariate logistic regression analysis for successful recanalization was performed.

RESULTS

Successful recanalization was achieved in 40% of patients (10/25) and showed a significantly higher FLAIR intensity (p=0.014). The cut-off value for clot intensity on the FLAIR sequence to predict recanalization was 0.7952, with 70% sensitivity and 80% specificity (95% CI 0.59 to 0.96) using a receiver operating characteristic curve. In multivariate logistic regression analysis, only a high FLAIR clot intensity (>0.7952) was associated with successful recanalization (OR 16.79; 95% CI 1.29 to 218.92; p=0.031).

CONCLUSIONS

High signal intensity on FLAIR clot imaging may predict successful recanalization after endovascular therapy for ICA-T occlusion.

An updated definition of stroke for the 21st century: a statement for healthcare professionals from the American Heart Association/American Stroke Association

Despite the global impact and advances in understanding the pathophysiology of cerebrovascular diseases, the term "stroke" is not consistently defined in clinical practice, in clinical research, or in assessments of the public health. The classic definition is mainly clinical and does not account for advances in science and technology. The Stroke Council of the American Heart Association/American Stroke Association convened a writing group to develop an expert consensus document for an updated definition of stroke for the 21st century. Central nervous system infarction is defined as brain, spinal cord, or retinal cell death attributable to ischemia, based on neuropathological, neuroimaging, and/or clinical evidence of permanent injury. Central nervous system infarction occurs over a clinical spectrum: Ischemic stroke specifically refers to central nervous system infarction accompanied by overt symptoms, while silent infarction by definition causes no known symptoms. Stroke also broadly includes intracerebral hemorrhage and subarachnoid hemorrhage. The updated definition of stroke incorporates clinical and tissue criteria and can be incorporated into practice, research, and assessments of the public health.

What is meant by "TICI"?

BACKGROUND

In 2003, Higashida et al proposed the Thrombolysis In Cerebral Infarction scale to evaluate angiographic intracranial flow. Our aim is to review how subsequently published studies define TICI.

MATERIALS AND METHODS

We used the ISI Web of Knowledge and SciVerse Scopus databases to search for "TICI" and "thrombolysis in cerebral infarction" and for articles that cited the original TICI paper from January 2004 through May 2012. Articles were categorized according to their definition of the TICI categories, typically grades 0-4, with grade 2 (partial reperfusion) subdivided into 2a and 2b, and rate of contrast entry to the perfused area. In addition, we catalogued the type of redefinitions of TICI subcategory 2 and additions of new categories.

RESULTS

Of 236 articles screened, 74 were included. Eight (11%) explicitly followed the TICI scale as originally defined. Thirty-seven (50%) cited Higashida but did not define their scale. Fifteen (21%) used and explained modified scales. Thirteen (18%) used the term TICI, but did not define the scale and did not cite Higashida. Eighteen (24%) specified a 2a subcategory. Nine defined grade 2a as <67% filling, 6 defined it as <50%, and 3 did not offer a percentage. Two studies added a 2c subcategory. Fifty-two (70%) used a cutoff level to define "successful reperfusion." Of these, 65% used TICI ≥2, 33% used TICI ≥2b, and 2% used TICI = 3.

CONCLUSIONS

There is substantial variability in the definition and/or application of the TICI scale in the literature. This variability could considerably impact our understanding of results of revascularization studies.

Histopathologic evaluation of arterial wall response to 5 neurovascular mechanical thrombectomy devices in a swine model

BACKGROUND AND PURPOSE

Five commercial devices are available for mechanical thrombectomy in acute ischemic stroke. This study evaluated and compared the resultant arterial damage from these devices.

MATERIALS AND METHODS

Wall damage after 4 wall-contact devices (the Merci retriever, Catch thromboembolectomy system, and Solitaire FR revascularization devices of 4 and 6 mm) and 1 aspiration device (the Penumbra System) was evaluated in the superficial femoral arteries of 20 male swine. Each device was tested with and without intraluminal clot. Twenty control vessels were not subjected to any intervention. Acute histopathologic changes were evaluated.

RESULTS

In the device samples, endothelial denudation (72.8 ± 29.4% versus 0.9 ± 1.9%, P < .0001), medial layer edema (52 ± 35.9% versus 18.1 ± 27.8%, P = .004), and mural thrombus (5.3 ± 14.2% versus 0%, P = .05) were found to a greater extent compared with the control samples. The aspiration device provoked more intimal layer (100 ± 79.1% versus 58.8 ± 48.9%, P = .27) and medial layer (75 ± 35.4% versus 46.3 ± 34.8%, P = .13) edema than the wall-contact devices.

CONCLUSIONS

All devices caused vascular injuries extending into the medial layer. The aspiration device was associated with more intimal and medial layer edema, compared with the wall-contact devices except for the Catch thromboembolectomy system.

Does mechanical thrombectomy in acute embolic stroke have long-term side effects on intracranial vessels? An angiographic follow-up study

PURPOSE

Mechanical thrombectomy (mTE) proved to be effective treating acute vessel occlusions with an acceptable rate of procedural complications. Potential long-term side effects of the vessel wall trauma caused by mechanical irritation of the endothelium are unknown up to now.

METHODS

From a retrospectively established database of 640 acute stroke treatments, we selected 261 patients with 265 embolic vessel occlusions treated successfully by mTE without permanent implantation of a stent. Analysis comprised the type of devices used and the number of passes performed. Digital subtraction angiography immediately after treatment was evaluated for vasospasm, dissection, and extravasation. Control angiographic images were evaluated for any morphological change compared to the immediate posttreatment angiographic run.

RESULTS

Recanalization was achieved with a median of one (range 1-10) mTE maneuvers. Vasospasm occurred in 69 territories (26.0 %) and was treated with glyceroltrinitrate in three. Dissection was observed in one vessel (0.4 %). Intraprocedural hemorrhage in two patients (0.8 %) was either wire or device induced. Follow-up digital subtraction angiography was available for 117 territories after a median of 107 days, revealing target vessel occlusion in one segment (0.9 %) and a de novo stenosis of four segments (3.4 %). All findings were clinically asymptomatic. Posttreatment vasospasm was more frequent in patients with de novo stenosis and occlusion (p = 0.038).

CONCLUSION

De novo stenoses and occlusions occur in a small proportion of patients after mTE. Because all lesions were clinically asymptomatic, this finding does not affect the overall benefit of the treatment. Vasospasm may predict late vessel wall changes.

Future trials of endovascular mechanical recanalisation therapy in acute ischemic stroke patients - a position paper endorsed by ESMINT and ESNR : part II: methodology of future trials

Based on current data and experience, the joint working group of the European Society of Minimally Invasive Neurological Therapy (ESMINT) and the European Society of Neuroradiology (ESNR) make suggestions on trial design and conduct aimed to investigate therapeutic effects of mechanical thrombectomy (MT). We anticipate that this roadmap will facilitate the setting up and conduct of successful trials in close collaboration with our neighbouring disciplines.

The impact of thromboemboli histology on the performance of a mechanical thrombectomy device

BACKGROUND AND PURPOSE

Recently we published a novel method of thrombus preparation for use in a swine model for evaluation of thrombectomy designs. The clot (fibrin rich clot) is characterized by its similarity in histologic characteristics to the thromboemboli recovered from stroke patients. The purpose of this latest study was to evaluate if the performance of a mechanical thrombectomy device was affected by the histologic characteristics of thromboembolus. Erythrocyte rich clot, which was created using exogenous thrombin, and the novel experimental clot with abundance of fibrin/cellular component were used for comparison. The Merci clot retriever was used for the evaluation and the angiographic outcomes were analyzed.

MATERIALS AND METHODS

Two histologically different types of experimental clot, a conventionally used thrombin-induced clot (erythrocyte-rich clot) and a novel experimental clot that is similar in histologic characteristics to the thromboemboli recovered from patients with stroke (fibrin-rich clot), were prepared. Eight extracranial arteries in swine were occluded with erythrocyte-rich clot (group A), and 8 were occluded with fibrin-rich clot (group B), and MT by using the Merci clot retriever device was performed. Angiographic results in each group were evaluated.

RESULTS

A total of 48 attempts at MT were made. The average number of attempts to achieve TIMI grade II or III recanalization was 2.75 times in group A and 4.5 times in group B (P < .001), respectively. The mean time to achieve recanalization was 15.5 minutes in group A and 81.5 minutes in group B (P < .01). Every vessel in group A showed recanalization (100%), whereas only 3 of 8 samples (37.5%) achieved recanalization in group B.

CONCLUSIONS

In this model, arteries occluded by fibrin-rich clot demonstrated a significantly lower recanalization rate, lower final TIMI score, and a longer mean recanalization time than did arteries occluded by erythrocyte-rich clot. The angiographic outcome of MT by using the Merci clot retriever system was influenced by the histologic characteristics of the occluding thromboembolus.

Correlative magnetic resonance imaging and autopsy findings in a patient with coagulation necrosis treated with tissue plasminogen activator

Coagulation necrosis is a peculiar type of ischemic necrosis that is characterized by firm, eosinophilic parenchyma with recognizable cell outlines without massive glial reactions. This is an autopsy report of coagulation necrosis 6 months after thrombolytic tissue plasminogen activator therapy against massive cerebral embolism in an 84-year-old man with atrial fibrillation.

Histopathologic evaluation of basilar artery atherosclerosis

INTRODUCTION

There has been limited attention to pathological features of basilar artery atherosclerosis. It has been assumed that pathology of basilar artery atherosclerosis mimics that of other vascular beds.

METHODS

To define the nature of the basilar artery atherosclerotic lesions, we analyzed postmortem intracranial artery samples from eight subjects with history of stroke.

RESULTS

Atherosclerotic lesions were present in 7/8 arteries examined, with a mean estimated stenosis of 34%. Lumen thrombus with a disrupted fibrous cap was seen in 1 lesion; the remaining 6 lesions revealed a thick fibrous cap. Neovascularity and calcification were seen in 1 lesion and mild to moderate inflammation was seen in 3 lesions. Necrotic core was present in 4/7 lesions, and was associated with plaque rupture in the only disrupted lesion.

CONCLUSIONS

Basilar artery atherosclerotic lesions were relatively benign in this series of patients presenting with stroke. While confirmation is needed with larger sample size, the relative paucity of neovascularity suggests a possibly distinctive histopathological profile.

CT and MRI early vessel signs reflect clot composition in acute stroke

BACKGROUND AND PURPOSE

The purpose of this study was to provide the first correlative study of the hyperdense middle cerebral artery sign (HMCAS) and gradient-echo MRI blooming artifact (BA) with pathology of retrieved thrombi in acute ischemic stroke.

METHODS

Noncontrast CT and gradient-echo MRI studies before mechanical thrombectomy in 50 consecutive cases of acute middle cerebral artery ischemic stroke were reviewed blinded to clinical and pathology data. Occlusions retrieved by thrombectomy underwent histopathologic analysis, including automated quantitative and qualitative rating of proportion composed of red blood cells (RBCs), white blood cells, and fibrin on microscopy of sectioned thrombi.

RESULTS

Among 50 patients, mean age was 66 years and 48% were female. Mean (SD) proportion was 61% (±21) fibrin, 34% (±21) RBCs, and 4% (±2) white blood cells. Of retrieved clots, 22 (44%) were fibrin-dominant, 13 (26%) RBC-dominant, and 15 (30%) mixed. HMCAS was identified in 10 of 20 middle cerebral artery stroke cases with CT with mean Hounsfield Unit density of 61 (±8 SD). BA occurred in 17 of 32 with gradient-echo MRI. HMCAS was more commonly seen with RBC-dominant and mixed than fibrin-dominant clots (100% versus 67% versus 20%, P=0.016). Mean percent RBC composition was higher in clots associated with HMCAS (47% versus 22%, P=0.016). BA was more common in RBC-dominant and mixed clots compared with fibrin-dominant clots (100% versus 63% versus 25%, P=0.002). Mean percent RBC was greater with BA (42% versus 23%, P=0.011).

CONCLUSIONS

CT HMCAS and gradient-echo MRI BA reflect pathology of occlusive thrombus. RBC content determines appearance of HMCAS and BA, whereas absence of HMCAS or BA may indicate fibrin-predominant occlusive thrombi.