A swine model to analyze arterial structural changes induced by mechanical thrombectomy

Impact of Target Artery Size on the Performance of Aspiration Thrombectomy: Insights from a Swine Model with Real-Time Visualization

A novel swine model was developed to investigate the underlying reasons for the failure of aspiration thrombectomy. The model allows direct visualization of the target artery during thrombectomy in vessels of different sizes. The behavior of the target artery undergoing aspiration thrombectomy was recorded with high-resolution digital microscopy and fluoroscopic visualization, providing valuable insight into how the different sizes of treated arteries affect the effectiveness of mechanical thrombectomy.

Preclinical testing platforms for mechanical thrombectomy in stroke: a review on phantoms, in-vivo animal, and cadaveric models

Preclinical testing platforms have been instrumental in the research and development of thrombectomy devices. However, there is no single model which fully captures the complexity of cerebrovascular anatomy, physiology, and the dynamic artery-clot-device interaction. This article provides a critical review of phantoms, in-vivo animal, and human cadaveric models used for thrombectomy testing and provides insights into the strengths and limitations of each platform. Articles published in the past 10 years that reported thrombectomy testing platforms were identified. Characteristics of each test platform, such as intracranial anatomy, artery tortuosity, vessel friction, flow conditions, device-vessel interaction, and visualization, were captured and benchmarked against human cerebral vessels involved in large-vessel occlusion stroke. Thrombectomy phantoms have been constructed from silicone, direct 3D-printed polymers, and glass. These phantoms represent oversimplified patient-specific cerebrovascular geometry but enable adequate visualization of devices and clots under appropriate flow conditions. They do not realistically mimic the artery-clot interaction. For the animal models, arteries from swine, canines, and rabbits have been reported. These models can reasonably replicate the artery-clot-device interaction and have the unique value of evaluating the safety of thrombectomy devices. However, the vasculature geometries are substantially less complex and flow conditions are different from human cerebral arteries. Cadaveric models are the most accurate vascular representations but with limited access and challenges in reproducibility of testing conditions. Multiple test platforms should be likely used for comprehensive evaluation of thrombectomy devices. Interpretation of the testing results should take into consideration platform-specific limitations.

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.

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.

Repeated Endovascular Thrombectomy in Patients With Acute Ischemic Stroke

Background and Purpose—

Patients with acute ischemic stroke treated with endovascular thrombectomy may be treated with repeat endovascular thrombectomy (rEVT) in case of recurrent large vessel occlusion. Data on safety and efficacy of these interventions is scarce. Our aim is to report on frequency, timing, and outcome of rEVT in a large nation-wide multicenter registry.

Methods—

In the Netherlands, all patients with endovascular thrombectomy have been registered since 2002 (MR CLEAN Pretrial registry, MR CLEAN Trial [Multicenter Randomized Clinical Trial of Endovascular Treatment for Acute Ischemic Stroke in the Netherlands], and MR CLEAN Registry). We retrospectively reviewed these databases for anterior circulation rEVT cases. Patient characteristics, procedural data, and functional outcome (modified Rankin Scale at 90 days) were analyzed.

Results—

Of 3928 patients treated between 2002 and 2017, 27 (0.7%) underwent rEVT. Median time between first and second procedure was 78 (1–1122) days; 11/27 patients were re-treated within 30 days. Cardioembolism was the most common etiology (18 patients [67%]). In 19 patients (70%), recurrent occlusion occurred ipsilateral to previous occlusion. At 90 days after rEVT procedure, 44% of the patients had achieved functional independence (modified Rankin Scale score of 0–2), and 33% had died. Adverse events were 2/27 (7.4%) intracranial hemorrhage, 1/27 (3.7%) stroke progression, and 1/27 (3.7%) pneumonia.

Conclusions—

In this large nationwide cohort of patients with acute ischemic stroke treated with endovascular thrombectomy, rEVT was rare. Stroke cause was mainly cardio-embolic, and most recurrent large vessel occlusions in which rEVT was performed occurred ipsilateral. Although there probably is a selection bias on repeated treatment in case of recurrent large vessel occlusion, rEVT appears safe, with similar outcome as in single-treated cases.

Etiology of recurrent large vessel occlusions treated with repeated thrombectomy

BACKGROUND

Repeated mechanical thrombectomy for acute stroke treatment in individual patients has been proven feasible. However, less is known about the etiology of recurrent vessel occlusions after prior thrombectomy. We aimed to understand if the etiology of such recurrent events differs from the first stroke.

METHODS

Retrospectively, we identified all patients at our center who received a repeated mechanical thrombectomy between 2007 and 2019. Clinical data were retrieved from medical records. Etiology of stroke was evaluated retrospectively, and angiographic studies were revisited.

RESULTS

Twenty-three patients (1.5%) were identified. Median age was 68 years (IQR 56-77). Median NIHSS at first admission was 11 points (IQR 5-15). In nine cases (39.1%), the recurrent vessel occlusion was located exactly at the same position as the prior occlusion. Overall, five (21.7%) patients had a remarkable extracranial pathology as likely cause of stroke recurrence. In 16 patients (69.6%), the etiology of the first stroke and its recurrence was considered as likely being the same, mostly of cardioembolic or unknown origin. In the seven remaining patients (30.4%), the cause of stroke possibly differed from the first event, with five patients (21.7%) having a postinterventional intracranial intimal lesion as possible cause of stroke.

CONCLUSION

Incidence of repeated thrombectomy was low. However, the high number of patients with known origin of stroke etiology raises the question how their monitoring may be optimized. The number of patients with remarkable extracranial pathologies or intracranial endothelial lesions supports current clinical practice to pay attention to final angiographic series.

Prevention of neointimal hyperplasia induced by an endovascular stent via intravenous infusion of mesenchymal stem cells

OBJECTIVE

In-stent restenosis after percutaneous transluminal angioplasty and stenting (PTAS) due to neointimal hyperplasia is a potential cause of clinical complications, including repeated revascularization and ischemic events. Neointimal hyperplasia induced by an inflammatory response to the stent strut may be a possible mechanism of in-stent restenosis. Intravenous infusion of bone marrow-derived mesenchymal stem cells (MSCs) has been reported to show therapeutic efficacy for cerebral stroke, presumably by an antiinflammatory effect. This study aimed to determine whether MSCs can reduce or prevent neointimal hyperplasia induced by an endovascular stent.

METHODS

In this study, two types of bare metal stents were deployed using a porcine (mini-pig) model. One stent was implanted in the common carotid artery (CCA), which is considered quite similar to the human CCA, and the other was inserted in the superficial cervical artery (SCA), which is similar in size to the human middle cerebral artery. Angiographic images, intravascular ultrasound (IVUS) imaging, and microscopic images were used for analysis.

RESULTS

Angiographic images and IVUS studies revealed that intravenous infusion of MSCs immediately after deployment of stents prevented in-stent stenosis of the CCA and SCA. Histological analysis also confirmed that inflammatory responses around the stent struts were reduced in both the stented CCA and SCA in the mini-pig.

CONCLUSIONS

Intravenous infusion of MSCs inhibited the inflammatory reaction to an implanted stent strut, and prevented progressive neointimal hyperplasia in the stented CCA and SCA in a porcine model. Thus, MSC treatment could attenuate the recurrence of cerebral ischemic events after stenting.

Safety and Efficacy Evaluation of Aspiration Thrombectomy With Large Bore Catheters in a Porcine Model

OBJECTIVE

Thrombectomy with aspiration catheters has shown to be effective for treatment of intracranial large vessel occlusion (LVO). We present preclinical evaluation of the safety and efficacy of React68 and React71 (Medtronic PLC, Irvine, CA) catheters in animal models of LVO.

METHODS

In vivo evaluation of catheter safety was performed in superficial cervical, internal maxillary, and renal arteries in a porcine model with or without clot (LVO). Animals were survived for 3 days and 30 days. Angiographic outcomes, usability, and histological parameters were compared for treatment with React68, React71, and ACE68 (Penumbra, Alameda, CA) catheters.

RESULTS

The in vivo angiographic analysis in a porcine thrombectomy LVO model demonstrated that there was no statistically significant difference in the rate of Thrombolysis in Cerebral Infarction scale 2b/3 recanalization between React68, React71, and ACE68 catheters. There were no physical or neurologic deficits in any of the treated animals throughout the survival period. Histologic analysis showed statistically non-inferior safety profile of React68 and React71 catheters relative to ACE68 catheters, with minimal but similar mild internal elastic lamina disruption and smooth muscle loss, but a lack of inflammation, fibrin deposits, and changes in the adventitia at both time points examined.

CONCLUSIONS

React68 and React71 aspiration catheters have an excellent safety, efficacy, and usability profile in animal models of LVO.

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.

Large animals in neurointerventional research: A systematic review on models, techniques and their application in endovascular procedures for stroke, aneurysms and vascular malformations

Neuroendovascular procedures have led to breakthroughs in the treatment of ischemic stroke, intracranial aneurysms, and intracranial arteriovenous malformations. Due to these substantial successes, there is continuous development of novel and refined therapeutic approaches. Large animal models feature various conceptual advantages in translational research, which makes them appealing for the development of novel endovascular treatments. However, the availability and role of large animal models have not been systematically described so far. Based on comprehensive research in two databases, this systematic review describes current large animal models in neuroendovascular research including their primary use. It may therefore serve as a compact compendium for researchers entering the field or looking for opportunities to refine study concepts. It also describes particular applications for ischemic stroke and aneurysm therapy, as well as for the treatment of arteriovenous malformations. It focuses on most promising study designs and readout parameters, as well as on important pitfalls in endovascular translational research including ways to circumvent them.

Neurosonography After Mechanical Thrombectomy for Acute Stroke Treatment

BACKGROUND AND PURPOSE

Mechanical thrombectomy has been shown to be effective for acute stroke treatment, but lesions of cerebral vessels can develop thereafter. Such lesions of recanalized vessels and altered cerebral hemodynamics after mechanical thrombectomy are poorly investigated. In particular for neurosonography, data are sparse. We aimed to describe hemodynamic changes and incidence of de-novo stenosis after mechanical thrombectomy with neurosonography.

METHODS

Retrospective analysis of patients after successful mechanical thrombectomy for acute stroke therapy who received one neurosonography at baseline and during follow up. Peak systolic velocity (PSV) of all intracranial recanalized and reference vessels was extracted for analysis. Patients with an isolated increase or decrease of PSV (50% or 50 cm/second for anterior and 30% or 30 cm/second for posterior circulation) were identified and characterized.

RESULTS

Eighty-eight patients (mean age 64.4; 34.1% female) were included in this study. In 9 (10.2%) patients, the vessel occlusion was located in the posterior, and in 79 (89.9%) patients the vessel occlusion was located in the anterior circulation. With predominance to the recanalized vessel, mean PSV decreased at both, the recanalized and the reference vessel during follow up. In 3 (3.4%) patients, an isolated increase of PSV was observed in the recanalized vessel, and in 6 (6.8%) patients an isolated decrease of PSV was observed in the recanalized vessel.

CONCLUSION

Sonographic incidence of de-novo stenosis following mechanical thrombectomy seems to be low, in line with prior angiographic studies. However, as measured by neurosonography, cerebral hemodynamic in the recanalized vessel is dynamic after thrombectomy. This result is of interest for further prospective analysis.

Comparison of Subacute Vascular Damage Caused by ADAPT versus Stent Retriever Devices after Thrombectomy in Acute Ischemic Stroke: Histological and Ultrastructural Study in an Animal Model

Objectives

To assess the delayed (15 days) histological and ultrastructural changes occurring following endovascular treatment with a direct aspiration first pass technique (ADAPT) or stent retrievers (SRs) and to compare the findings in order to determine which is the least harmful technique and what changes occur.

Materials and Methods

Damage to the wall of swine extracranial arteries was evaluated after ADAPT with the Penumbra system or thrombectomy with various SRs. The procedures were performed using two pigs as animal models; extracranial cervical arteries were selected based on their diameters in order to reproduce the procedures as in human intracranial arteries, and endovascular thrombectomies were done after the injection of autologous thrombi. Two weeks later, the animals were euthanized, and 60 arterial samples were obtained for analysis by optical and electron microscopy.

Results

Optical and electron microscopy revealed that both techniques cause, in different way, alterations to the structure of the vessel wall.

Conclusions

Both techniques caused damage to the vessel wall. The main damages were localized at the level of the tunica media and adventitia, instead of the tunica intima as in the acute phase. Further investigation is required to better understand whether these alterations could have chronic consequences.

Characterization of thrombus stiffening in radio frequency (rf) Mechanical thrombectomy

Intra-arterial mechanical thrombectomy (IAMT) for ischemic stroke has high recanalization rate, long treatment time window and low risk of symptomatic intracerebral haemorrhage (sICH), but thrombus fragments produced during treatment can lead to distal embolization. Fragmentation can be reduced if the thrombus is strengthened by increasing the thrombus's crosslink density. Radio frequency (rf) electric current commonly used in surgery to cut and coagulate tissue can induce crosslinking in thrombus. The increase in thrombus stiffness as a result of the increase in crosslinking from rf treatment is characterized in this study. Test results showed that the stiffness of thrombus is increased by more than 8 times after rf treatment. The dramatic increase in stiffness suggests that thrombus fragmentation and distal embolization can be reduced by applying rf during thrombectomy treatment.

Mechanical thrombectomy with the Solitaire AB stent for treatment of acute basilar artery occlusion: A single-center experience

Basilar artery occlusion (BAO) remains one of the most devastating subtypes of ischemic stroke, and prognosis is poor if early recanalization is not achieved. The purpose of this study was to evaluate the safety and technical feasibility of mechanical thrombectomy with the Solitaire AB stent (Covidien, Irvine, CA, USA) for the treatment of acute BAO through a single-center experience. Twenty-one patients with acute BAO were treated with mechanical thrombectomy with the Solitaire AB stent device between 1st September 2011 and 1st December 2014. Recanalization was assessed using the Thrombolysis in Cerebral Infarction (TICI) scale system. Clinical outcome was established at discharge by The National Institute of Health Stroke Scale (NIHSS), and the mean time from symptom onset to recanalization determined. Authors had access to identifying information during or after data collection. The clinical status of patients on admission was severe, with a mean NIHSS score of 25.57±5.20 (range: 16-38), and the number of patients with TICI 2b or 3 was 0. The mean time from symptom onset to recanalization was 579.00±188.78min (range: 360-960min). At 3-month follow-up, eight (38.1%) patients had a good clinical outcome. At follow-up, the trial of ORG 10172 in acute stroke treatment (TOAST) classification was large-vessel atherosclerosis in 13 patients (61.9%), cardioembolic in seven patients (33.3%), and undetermined in one patient (4.8%). In our series, application of the Solitaire AB stent retriever in acute BAO resulted in a high recanalization rate without procedural complications, and with good clinical outcome. Further prospective trials are needed to confirm the potential clinical benefit of this treatment approach.

A Novel Canine Model of Acute Vertebral Artery Occlusion

Background

The extended time window and theoretic reduction in hemorrhage make mechanical strategies an attractive approach for the treatment of patients with ischemic stroke. However, a limited availability of suitable animal models of cerebrovascular thrombosis has hampered the study of novel endovascular interventions. The aim of the present study was to develop a new technique for site-specific placement of a thrombus in a canine model that would allow for the evaluation of mechanical thrombectomy and clot retrieval methods and the visualization of thrombus dislocation or fragmentation during angiographic manipulation.

Methods

Angiography and embolization with a preformed thrombus were performed in 12 canines. Under fluoroscopic guidance, an embolism protection device (EPD) was anchored to the middle segment of the left vertebral artery (VA) via the left femoral arterial sheath. A preformed radiopaque clot was injected through the guide catheter into the left VA, via the contralateral femoral artery, proximal to the EPD. After 15 min of occlusion, the EPD was removed and persistent occlusion of the VA was documented angiographically.

Results

Angiography performed during the observation period confirmed the persistence of VA occlusion in each case, and displacement of the radiopaque clots did not occur during the 3-hour observation period. The technique allowed selective embolization of targeted vessels without thrombus fragmentation.

Conclusion

This study demonstrates, for the first time, a canine model of post-circulation embolism induced by autologous blood clot placement. This model can be rapidly formed and easily operated, and the site of thrombosis can be readily controlled.

Delayed Stenosis in the Intracranial Vessels following Endovascular Treatment for Acute Stroke

PURPOSE

To evaluate delayed stenosis of the vessels after endovascular thrombectomy using magnetic resonance (MR) angiography.

MATERIALS AND METHODS

Of 82 consecutive patients who underwent successful endovascular treatment for acute intracranial large vessel occlusion between October 2010 and October 2014 at a single institution, 57 patients for whom 3-month radiologic follow-up examinations using MR angiography were available were included in the analysis. MR angiography images were assessed to detect delayed stenosis, which was defined as a decrease in the diameter of treated vessels > 50% compared with MR angiography images obtained 24 hours after endovascular treatment.

RESULTS

MR angiography images obtained 3 months after endovascular treatment revealed delayed stenosis of treated vessels in five (8.8%) of 57 patients. All cases of delayed stenosis were asymptomatic and occurred in the middle cerebral artery (MCA). Further serial radiologic follow-up showed gradual improvement of all delayed stenosis over 12 months.

CONCLUSIONS

Endovascular treatment poses a risk of delayed stenosis of treated vessels, especially in the MCA. MR angiography is a useful modality in long-term follow-up to evaluate delayed stenosis after endovascular treatment.

In-vitro testing of RF-enabled low force mechanical thrombectomy for ischemic stroke

Mechanical thrombectomy for ischemic stroke has high recanalization rate, long treatment time window and low hemorrhage risk. However, the clot engagement approach of caging the clot against the vessel wall can cause vessel stenosis and stroke recurrence. A device with reduced radial stenting force that reduces vessel wall friction would minimize stenosis and damage. The use of localized Radio Frequency (RF) to enable clot engagement and retrieval with minimal stenting force is explored in this study. New mechanical thrombectomy devices enabled with RF (Patent No.: US 62/172,043) were built and tested on human blood clots in vessels ex vivo. Test results showed that the RF-mechanical thrombectomy successfully and reproducibly captured and retrieved the clots without relying on stent caging of the clot against the vessel wall. Further work will be conducted on animals to compare vessel wall damage between conventional and RF-mechanical thrombectomy.

Evaluation of the JRecan device for thrombus retrieval: efficacy and safety in a swine model of acute arterial occlusion

OBJECTIVE

To evaluate the recanalization efficacy and safety of a novel stent retriever in a swine model of acute arterial occlusion.

METHODS

The JRecan thrombectomy device, a stent retriever with a weaving stent design, was evaluated in 18 occluded cervicocerebral vessels of swine. The flow restoration effect immediately upon deployment, the reperfusion rate after retrieval, thromboembolic events, and complications were assessed. The histologic structure of the renal arteries after retriever passage was measured to further assess the safety of JRecan.

RESULTS

Immediate flow restoration was achieved in 66.7% of occlusions (12/18). The reperfusion rate was 94.4% (two Thrombolysis in Cerebral Infarction (TICI) 2b and 15 TICI 3). Distal thromboembolic events did not occur. Microscopic examination of the arteries after retrieval showed mild degrees of endothelial loss in 96.6% (29/30), fibrin or platelet deposition in 53.3% (16/30), and disruption of the internal elastic lamina in 10% (3/30), without severe pathologic lesions.

CONCLUSIONS

The JRecan is highly effective at clot removal with a favorable safety profile and merits further development as a stent retriever for the treatment of acute ischemic stroke.

New method of thrombus preparation using a fluid model for evaluation of thrombectomy devices in a swine model

BACKGROUND

Mechanical thrombectomy is a promising new modality of interventional stroke treatment. Preparation of thrombus is a very important step for the evaluation of the mechanical thrombectomy devices. The objective of this study was to explore a new method of thrombus preparation with fluid model (FM) for assessment of thrombectomy devices used in the recanalization of acute ischemic stroke.

METHODS

Elongation test and catheter injection test were used to evaluate the mechanical properties of thrombi prepared by FM and static model (SM). Histological structures of two artificial clots and specimens of stroke patients were compared. Radiopacity of thrombus made by FM was evaluated in a swine embolization model.

RESULTS

The maximum tensile length of thrombi prepared by FM and SM were significantly higher (4.28 ± 0.23 cm vs 3.16 ± 0.13 cm, P < 0.01) and showed less breakage on catheter injection test (13% vs 60%, P < 0.05). Histological features of thrombi prepared by FM showed mixed thrombus structure, similar to thromboemboli retrieved from acute stroke patients, while clots generated by SM were replete with erythrocytes. A total of twelve vessels in two swine were successfully occluded (TIMI 0 or 1), with sufficient radiopacity of each injected thrombus.

CONCLUSION

The thrombus prepared by FM had good mechanical stability, sufficient radiopacity, and similar histological structure of thromboemboli retrieved from stroke patients, which make it possible to be used in the evaluation of thrombectomy devices.

A novel Swine model to evaluate arterial vessel injury after mechanical endovascular thrombectomy

Few animal models have been reported to evaluate and compare mechanical endovascular thrombectomy (MET) devices used to treat human ischemic stroke. These models may contribute to the understanding of arterial injury induced by a MET device and potentially by extrapolation to human intracranial arteries. We have developed a novel swine model for MET that allows visualization of the thrombus/device interaction and characterization of mechanical impact on the vessel wall. Twenty superficial femoral arteries were occluded with radiopaque thrombus, and 20 without thrombus were treated with thrombectomy devices. Acute histopathological changes were evaluated. The swine femoral artery, which is comparable in size to the human middle cerebral artery or basilar artery, may offer a useful animal model for the study of histologic alterations induced by MET.

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.