Stent retriever thrombectomy with the Cover accessory device versus proximal protection with a balloon guide catheter: in vitro stroke model comparison

Combined Aspiration and Stent Retriever Thrombectomy for Distal Carotid Artery Occlusion Using Balloon Guide versus Non-Balloon Guide Catheter

Background: The introduction of endovascular thrombectomy dramatically changed acute stroke management and became the standard treatment. Balloon guide catheters provide flow arrest during the clot retrieval process and have several advantages.This study aimed to compare balloon guide catheters (BGCs) versus non-balloon guide catheters (NBGCs) as a part of a combined treatment modality in patients presenting with acute ischemic stroke. Methods: This retrospective study included n = 65 patients who underwent a combined endovascular stroke treatment for distal internal carotid artery (ICA) occlusion. Patients underwent aspiration and stent retriever thrombectomy with the use of BGCs (Group 1, n = 27) or NBGCs (Group 2, n = 38). Results: The groups were compared for outcomes: the National Institutes of Health Stroke Scale (NIHSSS) score change, successful recanalization, good functional outcome at three months, and in-hospital mortality. Conclusion: The two groups didn't differ in terms of the NIHSS score change compared to baseline (p > 0.05). Moreover, there were no significant differences between the two groups in terms of the successful recanalization rate, three-month favorable functional outcome rate, and in-hospital mortality (p = 0.292, p = 0.952, p = 0.178), respectively. Further prospective studies with a larger number of patients and better methodology are warranted.

In vitro models for the experimental evaluation of mechanical thrombectomy devices in acute ischemic stroke

Mechanical thrombectomy has become an important method for the treatment of acute ischemic stroke for large vessel occlusions. The current hotspots of mechanical thrombectomy are optimizing the treatment methods, improving the recanalization rate and reducing complications. The in vitro model has become a common and convenient method for mechanical thrombectomy research. This review summarizes the in vitro model in the following aspects: the preparation of clot analogues; the experimental platform; the application of the in vitro model in the testing of thrombectomy devices; and the advantages, limitations and future trends of the in vitro experimental model. This review describes the characteristics and applications of the in vitro experimental model with the hope that the in vitro experimental model will be further improved and play a more effective role in the study of mechanical thrombectomy.

3D-Printed Disease Models for Neurosurgical Planning, Simulation, and Training

Spatial insight into intracranial pathology and structure is important for neurosurgeons to perform safe and successful surgeries. Three-dimensional (3D) printing technology in the medical field has made it possible to produce intuitive models that can help with spatial perception. Recent advances in 3D-printed disease models have removed barriers to entering the clinical field and medical market, such as precision and texture reality, speed of production, and cost. The 3D-printed disease model is now ready to be actively applied to daily clinical practice in neurosurgical planning, simulation, and training. In this review, the development of 3D-printed neurosurgical disease models and their application are summarized and discussed.

Comparison of fluid dynamics changes due to physical activity in 3D printed patient specific coronary phantoms with the Windkessel equivalent model of coronary flow

Background

3D printing (3DP) used to replicate the geometry of normal and abnormal vascular pathologies has been demonstrated in many publications; however, reproduction of hemodynamic changes due to physical activities, such as rest versus moderate exercise, need to be investigated. We developed a new design for patient specific coronary phantoms, which allow adjustable physiological variables such as coronary distal resistance and coronary compliance in patients with coronary artery disease. The new design was tested in precise benchtop experiments and compared with a theoretical Windkessel electrical circuit equivalent, that models coronary flow and pressure using arterial resistance and compliance.

Methods

Five phantoms from patients who underwent clinically indicated elective invasive coronary angiography were built from CCTA scans using multi-material 3D printing. Each phantom was used in a controlled flow system where patient specific flow conditions were simulated by a programmable cardiac pump. To simulate the arteriole and capillary beds flow resistance and the compliance for various physical activities, we designed a three-chamber outlet system which controls the outflow dynamics of each coronary tree. Benchtop pressure measurements were recorded using sensors embedded in each of the main coronary arteries. Using the Windkessel model, patient specific flow equivalent electrical circuit models were designed for each coronary tree branch, and flow in each artery was determined for known inflow conditions. Local flow resistances were calculated through Poiseuille’s Law derived from the radii and lengths of the coronary arteries using CT angiography based multi-planar reconstructions. The coronary stenosis flow rates from the benchtop and the electrical models were compared to the localized flow rates calculated from invasive pressure measurements recorded in the angio-suites.

Results

The average Pearson correlations of the localized flow rates at the location of the stenosis between each of the models (Benchtop/Electrical, Benchtop/Angio, Electrical/Angio) are 0.970, 0.981, and 0.958 respectively.

Conclusions

3D printed coronary phantoms can be used to replicate the human arterial anatomy as well as blood flow conditions. It displays high levels of correlation when compared to hemodynamics calculated in electrically-equivalent coronary Windkessel models as well as invasive angio-suite pressure measurements.

Endovascular Transcarotid Artery Revascularization Using the Walrus Balloon Guide Catheter: Preliminary Experience

BACKGROUND

The Walrus Balloon Guided System Catheter is a new generation of balloon guide catheter (BGC) designed to bypass some technical limitations of conventional BGC devices. Their utility in cervical carotid disease treatment has not been reported. We report our preliminary experience in cervical carotid treatment using the Walrus BGC to perform a modified endovascular transcarotid artery revascularization technique.

METHODS

Patients with cervical carotid disease undergoing endovascular treatment using the Walrus BGC at our institution were identified. The pertinent baseline demographics and procedural outcomes were collected and analyzed.

RESULTS

Twelve patients were included (median age, 70; 58.3% females). All patients had an imaging-confirmed cervical carotid disease that indicated intervention: 6 with high-grade cervical arteriosclerotic carotid stenosis, 2 with intraluminal thrombi, 1 with traumatic carotid dissection, and 3 patients with cervical carotid tandem occlusion along with acute ischemic stroke secondary to large vessel occlusion that required mechanical thrombectomy. Carotid artery stenting was performed in all cases, except 2 of the 3 mechanical thrombectomy cases (angioplasty only). All patients had at least periprocedural follow-up of 30 days, with no stroke, myocardial infarction, or death encountered.

CONCLUSIONS

We describe a modified endovascular transcarotid artery revascularization technique. We used a standard femoral access to navigate the Walrus catheter in the common carotid artery, followed by balloon inflation for proximal flow arrest or flow reversal (when connected to the aspiration pump) to deploy the carotid stent across the stenosis, while avoiding distal external carotid artery balloon occlusion. Successful treatment was achieved in all cases, with no periprocedural complications encountered.

Use of patient specific 3D printed neurovascular phantoms to simulate mechanical thrombectomy

BACKGROUND

The ability of the patient specific 3D printed neurovascular phantoms to accurately replicate the anatomy and hemodynamics of the chronic neurovascular diseases has been demonstrated by many studies. Acute occurrences, however, may still require further development and investigation and therefore we studied acute ischemic stroke (AIS). The efficacy of endovascular procedures such as mechanical thrombectomy (MT) for the treatment of large vessel occlusion (LVO), can be improved by testing the performance of thrombectomy devices and techniques using patient specific 3D printed neurovascular models.

METHODS

3D printed phantoms were connected to a flow loop with physiologically relevant flow conditions, including input flow rate and fluid temperature. A simulated blood clot was introduced into the model and placed in the proximal Middle Cerebral Artery (MCA) region. Clot location, composition, length, and arterial angulation were varied and MTs were simulated using stent retrievers. Device placement relative to the clot and the outcome of the thrombectomy were recorded for each situation. Digital subtraction angiograms (DSA) were captured before and after LVO simulation. Recanalization outcome was evaluated using DSA as either 'no recanalization' or 'recanalization'. Forty-two 3DP neurovascular phantom benchtop experiments were performed.

RESULTS

Clot angulation within the MCA region had the most significant impact on the MT outcome, with a p-value of 0.016. Other factors such as clot location, clot composition, and clot length correlated weakly with the MT outcome.

CONCLUSIONS

This project allowed us to gain knowledge of how such characteristics influence thrombectomy success and can be used in making clinical decisions when planning the procedure and selecting specific thrombectomy tools and approaches.

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.

Transcirculation Embolization to New Territory During Mechanical Thrombectomy for Acute Ischemic Stroke

Embolization in new territories (ENT) is a known complication of mechanical thrombectomy with incidence dependent upon a variety of procedural factors. We present 2 cases of anterior circulation to posterior circulation ENT. These cases were managed with manual aspiration thrombectomy with excellent radiographic and clinical outcome. We present the available literature involving ENT along with our experience in management.

Comparison of Balloon Guide Catheters and Standard Guide Catheters for Acute Ischemic Stroke: A Systematic Review and Meta-Analysis

BACKGROUND

Balloon guide catheters (BGCs) are designed to induce flow arrest during mechanical thrombectomy procedures for acute ischemic stroke due to large-vessel occlusion and have been associated with improved clinical and angiographic outcomes. We conducted a systematic review and meta-analysis evaluating the relative technical and clinical outcomes associated with BGC versus non-BGC approaches.

METHODS

A systematic review of clinical literature using the PubMed database was undertaken to identify multiarm studies published between 2010 and 2021 reporting the use of BGC versus non-BGC approaches for stroke treatment. Data collected included complete recanalization (thrombolysis in cerebral infarction, TICI), first-pass effect TICI 3, puncture-to recanalization time, number of endovascular attempts, distal embolization, symptomatic intracerebral hemorrhage, 90-day modified Rankin Scale score 0-2, and 90-day mortality. Subgroup analyses assessed the impact of treatment device (stent-retrievers, contact aspiration, combination therapy, and not specified/other). A random effects model was fit for each outcome measure.

RESULTS

Fifteen studies were included. Compared with non-BGC approaches, patients treated with BGCs had greater odds of TICI 3 (odds ratio [OR] 1.57; 95% confidence interval [95% CI] 1.08-2.29) and first-pass effect TICI 3 (OR 3.63; 95% CI 2.34-5.62), reduced puncture-to-revascularization time (mean difference -7.8; 95% CI -13.3 to -2.2), fewer endovascular attempts (mean difference -0.47; 95% CI -0.68 to -0.26), reduced odds of distal emboli (OR 0.34; 95% CI 0.17-0.71) and symptomatic intracerebral hemorrhage (OR 0.66; 95% CI 0.51-0.86), greater odds of 90-day modified Rankin Scale score 0-2 (OR 1.51; 95% CI 1.27-1.79), and reduced odds of mortality (OR 0.69; 95% CI 0.57-0.82).

CONCLUSIONS

BGCs yield superior technical and clinical outcomes while reducing patient complications.

Challenges in hemodynamics assessment in complex neurovascular geometries using computational fluid dynamics and benchtop flow simulation in 3D printed patient specific phantoms

Purpose

Complex hemodynamics assessments, as those related to carotid stenosis, are not always easily straightforward due to multifaceted challenges presented by the collateral flow in the Circle of Willis (CoW) and brain flow autoregulation. Advanced computational and benchtop methods to investigate hemodynamics aspects related to such complex flows are often used, however both have limitations and could lead to results which may diverge. In this study we investigated these aspects by performing correlated computational fluid dynamics (CFD) simulations and benchtop experiments in patient specific 3D printed phantoms.

Materials and Methods

To investigate the flow in patients with carotid stenosis, we built two patient specific phantoms which contained the arterial lesion of interest, all main arteries leading to the brain, the CoW and main arteries branching from it. Each phantom was connected to a generic aortic arch. A programmable pump was connected and flow parameters were measured proximal and distal to the lesion and the contralateral arteries. The patient 3D geometry was used to perform a set of CFD simulations where inflow boundary conditions matched the experimental ones. Flow conditions were recorded at the same locations as the experimental setup. Further exploration into the translation from experimental to CFD was also performed by customizing vascular segmentation and physically manipulating arterial compliance properties.

Results

We initially observed significant differences between the CFD recordings and the experimental setup. Most of the differences were due to changes in phantom geometry when subjected to physiological pressures and simplistic outflow boundary conditions in the CFD simulations which do not account for pulsatility and nonlinear phenomena. Further work confirms the need for dynamic mesh behavior within CFD simulations attempting to computationally mimic 3D-printed benchtop experiments. Additionally, CFD simulation may benefit from considering geometry specific to a 3D-printed vascular phantom.

Evaluation of challenges and limitations of mechanical thrombectomy using 3D printed neurovascular phantoms

The mechanical thrombectomy (MT) efficacy, for large vessel occlusion (LVO) treatment in patients with stroke, could be improved if better teaching and practicing surgical tools were available. We propose a novel approach that uses 3D printing (3DP) to generate patient anatomical vascular variants for simulation of diverse clinical scenarios of LVO treated with MT. 3DP phantoms were connected to a flow loop with physiologically relevant flow conditions, including input flow rate and fluid temperature. A simulated blood clot was introduced into the model and placed in the Middle Cerebral Artery region. Clot location, composition (hard or soft clot), length, and arterial angulation were varied and MTs were simulated using stent retrievers. Device placement relative to the clot and the outcome of the thrombectomy were recorded for each situation. Angiograms were captured before and after LVO simulation and after the MT. Recanalization outcome was evaluated using the Thrombolysis in Cerebral Infarction (TICI) scale. Forty-two 3DP neurovascular phantom benchtop experiments were performed. Clot mechanical properties, hard versus soft, had the highest impact on the MT outcome, with 18/42 proving to be successful with full or partial clot retrieval. Other factors such as device manufacturer and the tortuosity of the 3DP model correlated weakly with the MT outcome. We demonstrated that 3DP can become a comprehensive tool for teaching and practicing various surgical procedures for MT in LVO patients. This platform can help vascular surgeons understand the endovascular devices limitations and patient vascular geometry challenges, to allow surgical approach optimization.

Design and Physical Properties of 3-Dimensional Printed Models Used for Neurointervention: A Systematic Review of the Literature

BACKGROUND

Three-dimensional (3D) printing has revolutionized training, education, and device testing. Understanding the design and physical properties of 3D-printed models is important.

OBJECTIVE

To systematically review the design, physical properties, accuracy, and experimental outcomes of 3D-printed vascular models used in neurointervention.

METHODS

We conducted a systematic review of the literature between January 1, 2000 and September 30, 2018. Public/Publisher MEDLINE (PubMed), Web of Science, Compendex, Cochrane, and Inspec databases were searched using Medical Subject Heading terms for design and physical attributes of 3D-printed models for neurointervention. Information on design and physical properties like compliance, lubricity, flow system, accuracy, and outcome measures were collected.

RESULTS

A total of 23 articles were included. Nine studies described 3D-printed models for stroke intervention. Tango Plus (Stratasys) was the most common material used to develop these models. Four studies described a population-representative geometry model. All other studies reported patient-specific vascular geometry. Eight studies reported complete reconstruction of the circle of Willis, anterior, and posterior circulation. Four studies reported a model with extracranial vasculature. One prototype study reported compliance and lubricity. Reported circulation systems included manual flushing, programmable pistons, peristaltic, and pulsatile pumps. Outcomes included thrombolysis in cerebral infarction, post-thrombectomy flow restoration, surgical performance, and qualitative feedback.

CONCLUSION

Variations exist in the material, design, and extent of reconstruction of vasculature of 3D-printed models. There is a need for objective characterization of 3D-printed vascular models. We propose the development of population representative 3D-printed models for skill improvement or device testing.

Endovascular treatment of cerebrovascular stenosis with stent for patients with ischemic cerebrovascular disease

This study aimed to investigate the therapeutic effect of cerebrovascular stent implantation in southwest Chinese patients with ischemic cerebrovascular disease and underlying risk factors for stent restenosis.We made a retrospectively analysis of occurring risk, cerebrovascular lesion, stent implantation, complication treatment, and prognosis of 54 patients with ischemic cerebrovascular disease in our department.A total of 85 stents were implanted into 54 patients, involving 44 of the internal carotid artery system, 34 of the vertebral-basal artery system and 7 of the subclavian artery system. All patients with stenosis were reduced by >70%, with all stenosis complete reduction in 5 (9%) patients and reduction of over 90% in 25 (46%) patients. A total of 50 patients were followed up for 28.5 (21-35) months. The stents in 42 patients exhibited satisfactory shape and location while restenosis occurred in 8 patients. Univariate analysis revealed that hyperlipidemia, hyperuricemia, surgery duration, and total length of hospital stay are significantly correlated with stent restenosis, and hyperlipidemia and hyperuricemia were proven to be independent risk factors for restenosis using logistic regression analysis.Cerebrovascular stent implantation and balloon inflation surgery can assist in abating angiostenosis and improving blood supplement effectively in patients with ischemic cerebrovascular disease. Besides, an overall evaluation, strict care, and regular check-up in perioperative period may reduce the occurrence of complications. Finally, several clinical parameters may need to be highly focused on in surgery for better prognosis.

Quantitative Characterization of Recanalization and Distal Emboli with a Novel Thrombectomy Device

PURPOSE

The first-pass effect during mechanical thrombectomy improves clinical outcomes regardless of first-line treatment approach, but current success rates for complete clot capture with one attempt are still less than 40%. We hypothesize that the ThrombX retriever (ThrombX Medical Inc.) can better engage challenging clot models during retrieval throughout tortuous vasculature in comparison with a standard stent retriever without increasing distal emboli.

MATERIALS AND METHODS

Thrombectomy testing with the new retriever as compared to the Solitaire stent retriever was simulated in a vascular replica with hard and soft clot analogs to create a challenging occlusive burden. Parameters included analysis of distal emboli generated per clot type, along with the degree of recanalization (complete, partial or none) by retrieval device verified by angiography.

RESULTS

The ThrombX device exhibited significantly higher rates of first-pass efficacy (90%) during hard clot retrieval in comparison with the control device (20%) (p < 0.009), while use of both techniques during soft clot retrieval resulted in equivalent recanalization. The soft clot model generated higher numbers of large emboli (>200 μm) across both device groups (p = 0.0147), and no significant differences in numbers of distal emboli were noted between the ThrombX and Solitaire techniques.

CONCLUSIONS

Irrespective of clot composition, use of the ThrombX retriever demonstrated high rates of complete recanalization at first pass in comparison with a state-of-the-art stent retriever and proved to be superior in the hard clot model. Preliminary data suggest that risk of distal embolization associated with the ThrombX system is comparable to that of the control device.

Method to simulate distal flow resistance in coronary arteries in 3D printed patient specific coronary models

BACKGROUND

Three-dimensional printing (3DP) offers a unique opportunity to build flexible vascular patient-specific coronary models for device testing, treatment planning, and physiological simulations. By optimizing the 3DP design to replicate the geometrical and mechanical properties of healthy and diseased arteries, we may improve the relevance of using such models to simulate the hemodynamics of coronary disease. We developed a method to build 3DP patient specific coronary phantoms, which maintain a significant part of the coronary tree, while preserving geometrical accuracy of the atherosclerotic plaques and allows for an adjustable hydraulic resistance.

METHODS

Coronary computed tomography angiography (CCTA) data was used within Vitrea (Vital Images, Minnetonka, MN) cardiac analysis application for automatic segmentation of the aortic root, Left Anterior Descending (LAD), Left Circumflex (LCX), Right Coronary Artery (RCA), and calcifications. Stereolithographic (STL) files of the vasculature and calcium were imported into Autodesk Meshmixer for 3D model optimization. A base with three chambers was built and interfaced with the phantom to allow fluid collection and independent distal resistance adjustment of the RCA, LAD and LCX and branching arteries. For the 3DP we used Agilus for the arterial wall, VeroClear for the base and a Vero blend for the calcifications, respectively. Each chamber outlet allowed interface with catheters of varying lengths and diameters for simulation of hydraulic resistance of both normal and hyperemic coronary flow conditions. To demonstrate the manufacturing approach appropriateness, models were tested in flow experiments.

RESULTS

Models were used successfully in flow experiments to simulate normal and hyperemic flow conditions. The inherent mean resistance of the chamber for the LAD, LCX, and RCA, were 1671, 1820, and 591 (dynes ∙ sec/ cm5), respectively. This was negligible when compared with estimates in humans, with the chamber resistance equating to 0.65-5.86%, 1.23-6.86%, and 0.05-1.67% of the coronary resistance for the LAD, LCX, and RCA, respectively at varying flow rates and activity states. Therefore, the chamber served as a means to simulate the compliance of the distal coronary trees and to allow facile coupling with a set of known resistance catheters to simulate various physical activity levels.

CONCLUSIONS

We have developed a method to create complex 3D printed patient specific coronary models derived from CCTA, which allow adjustable distal capillary bed resistances. This manufacturing approach permits comprehensive coronary model development which may be used for physiologically relevant flow simulations.

Endovascular Treatment of Acute Ischemic Stroke

급성 허혈성 뇌졸중은 심각한 후유증이나 사망에 이르는 가장 큰 원인 질환들 중 하나이다. 제2세대 혈전제거기구가 도입된 이후로 급성 허혈성 뇌졸중에서 혈관 내 재개통 치료는 급속히 발전해 왔고, 최근에는 표준 치료 중의 하나가 되었다. 이 종설에서는 급성 허혈성 뇌졸중에서 혈관 내 치료와 고식적인 치료를 무작위 배정으로 비교한 임상 연구들의 결과를 간략히 기술하고, 새로이 개정된 급성 허혈성 뇌졸중에서의 혈관 내 치료의 적응증과, 현재 혈관내 치료에 쓰이는 기구들과 방법에 대해 알아보고자 한다.

Acute ischaemic stroke interventions: large vessel occlusion and beyond

Care for acute ischaemic stroke is one of the most rapidly evolving fields due to the robust outcomes achieved by mechanical thrombectomy. Large vessel occlusion (LVO) accounts for up to 38% of acute ischaemic stroke and comes with devastating outcomes for patients, families and society in the pre-intervention era. A paradigm shift and a breakthrough brought mechanical thrombectomy back into the spotlight for acute ischaemic stroke; this was because five randomised controlled trials from several countries concluded that mechanical thrombectomy for acute stroke offered overwhelming benefits. This review article will present a comprehensive overview of LVO management, techniques and devices used, and the future of stroke therapy. In addition, we review our institution experience of mechanical thrombectomy for posterior and distal circulation occlusion.

Numerical modelling of blood clot extraction by aspiration thrombectomy. Evaluation of aspiration catheter geometry

Aspiration thrombectomy is one of the most effective systems for blood clot removal and vessel recanalization. We present the results of a study involving the modelling and extraction of blood clots in the arteries of the human body using the following computer tools: Bond-Graph methodology for the fluid domain and Multi-Body Simulation for the mechanical domain. The modelling for the mechanical domain focuses on the clot and the distal end section of an aspiration device. Our final model considers an elastic characterization of the blood clot with progressive detachment from the vessel wall. We conclude that the results of such modelling could potentially improve the effectiveness of blood clot removal by reducing the risk of clot fragmentation. Such modelling could also potentially provide an adjunct technique in improving recanalization of arteries over a range of given parameters (mechanical properties of the vessel, mechanical properties of the blood clot, blood clot length, suction pressure, catheter - clot distance, catheter shape, catheter diameter and vessel occlusion).

Predictors of Balloon Guide Catheter Assistance Success in Stent-retrieval Thrombectomy for an Anterior Circulation Acute Ischemic Stroke

Introduction Mechanical thrombectomy has become the standard treatment for large vessel occlusion (LVO) in acute ischemic stroke (AIS) in well-selected patients. Although many devices and strategies exist, the use of a balloon-tip guide catheter (BGC) with stent-retriever (SR) may hold several advantages. We aim to assess the efficacy and identify predictors of technical success of this unique approach. Methods From our prospectively maintained database, we identified consecutive cases in which a BGC was used for stent-retriever thrombectomy in anterior circulation LVO between 2015 and 2016. Baseline and procedural characteristics were captured and analyzed. Predictors of technical and clinical outcomes were identified by multivariable logistic regression analysis. Results Ninety-three patients with AIS-LVO were treated with BGC-assisted mechanical thrombectomy. The mean age was 71 years old (SD 14), with 49.5% male (n=46). Pre-operative IV-tPA was administered in 55.9% (n=52) of cases. The most common location of occlusive thrombus was M1 (64.5%, n=60). Successful recanalization (mTICI=2b-3) was achieved in 86.0% (n=80) of cases while complete revascularization (mTICI-3) was achieved in 56.5% (n=52). There was a first-pass success rate of 52.7% (n=49). At discharge, 38.7% of the patients were functionally independent (mRS≤2). Multivariate analysis revealed that the middle cerebral artery location was strongly predictive of first-pass success, resulting in mTICI =2b revascularization (OR 7.10, p=0.018). Additionally, female gender (OR 2.85, p=0.042) and decreasing mTICI were associated with a poor clinical outcome (mRS≥4; OR 1.76, p=0.008). Conclusions BGC assistance in stent retrieval thrombectomy is safe and effective for AIS due to anterior circulation LVO. Further investigation is required to elucidate the optimal treatment strategy based on patient and disease characteristics.

Longer 6-mm Diameter Stent Retrievers Are Effective for Achieving Higher First Pass Success with Fibrin-Rich Clots

First pass success (FPS) can be defined as in vitro retrieval of clot in a single pass during mechanical thrombectomy (MT) for acute large vessel occlusion (LVO). Despite advancements in MT technology, retrieval of fibrin-rich clots remains a challenge. Therefore, the effect of stent retriever length on FPS for fibrin-rich clots was investigated by using Solitaire^TM 6 × 40 versus 6 × 30 mm devices with a balloon guide catheter (BGC) or distal access catheter (DAC) and sheath, in an in vitro model of anterior circulation neurovascular anatomy. Additionally, vascular safety of the Solitaire^TM 6 × 40 versus 6 × 30 mm devices was evaluated in a porcine model for differences in: luminal thrombus, inflammation, endothelial coverage, fibrin deposits, smooth muscle cell loss, elastic lamina and adventitia disruption, intimal hyperplasia, and lumen reduction, at 0, 30, and 90 days post-treatment. In vitro overall FPS was measured as: Solitaire^TM 6 × 40 (95%) and Solitaire^TM 6 × 30 (67%). FPS for clot location in middle cerebral artery was: (a) BGC (6 × 40 mm: 100%; 6 × 30 mm: 100%; n = 8); (b) DAC with 088 sheath (6 × 40 mm: 83%; 6 × 30 mm: 33%; n = 12). FPS for clot location in internal carotid artery was: (a) BGC (6 × 40 mm: 100%; 6 × 30 mm: 80%; n = 11); (b) DAC with 088 sheath (6 × 40 mm: 100%; 6 × 30 mm: 67%; n = 10). Stent length had a significant effect (Fisher's exact test; p < 0.05) on FPS. In vivo evaluation in the porcine model showed no difference in vascular safety parameters between the Solitaire^TM 6 × 40 and 6 × 30 mm devices (p > 0.05) at all time points in the study. Longer stent retrievers may be safe and effective in improving FPS for fibrin-rich clots in in vitro and in vivo models of LVO.

The Effects of Balloon-Guide Catheters on Outcomes after Mechanical Thrombectomy in Acute Ischemic Strokes : A Meta-Analysis

Objective

Mechanical thrombectomies with balloon-guide catheters (BGC) are thought to improve successful recanalization rates and to decrease the incidence of distal emboli compared to thrombectomies without BGC. We aimed to assess the effects of BGC on the outcomes of mechanical thrombectomy in acute ischemic strokes.

Methods

Studies from PubMed, EMBASE, and the Cochrane library database from January 2010 to February 2018 were reviewed. Random effect model for meta-analysis was used. Analyses such as meta-regression and the “trim-and-fill” method were additionally carried out.

Results

A total of seven articles involving 2223 patients were analyzed. Mechanical thrombectomy with BGC was associated with higher rates of successful recanalization (odds ratio [OR], 1.632; 95% confidence interval [CI], 1.293–2.059). BGC did not significantly decrease distal emboli, both before (OR, 0.404; 95% CI, 0.108–1.505) and after correcting for bias (adjusted OR, 1.165; 95% CI, 0.310–4.382). Good outcomes were observed more frequently in the BGC group (OR, 1.886; 95% CI, 1.564–2.273). Symptomatic intracranial hemorrhage and mortality did not differ significantly with BGC use.

Conclusion

Our meta-analysis demonstrates that BGC enhance recanalization rates. However, BGC use did not decrease distal emboli after mechanical thrombectomies. This should be interpreted with caution due to possible publication bias and heterogeneity. Additional meta-analyses based on individual patient data are needed to clarify the role of BGC in mechanical thrombectomies.

Institutional and provider variations for mechanical thrombectomy in the treatment of acute ischemic stroke: a survey analysis

Introduction

Stent retriever combined with aspiration, or the ‘Solumbra technique’, has recently emerged as one of the popular methods of mechanical thrombectomy (MT). However, the variations in understanding and implementation of the Solumbra technique have not been reported.

Methods

An 18 part anonymous survey questionnaire was designed to extract information regarding technical variations of MT with a focus on the Solumbra technique. The survey link was posted on the Society of Neurointerventional Surgery (SNIS) website in ‘SNIS connect’.

Results

80 responses were obtained over 4 weeks that were included in the final analysis. Direct aspiration without a balloon guide catheter (BGC) was the most favored technique among respondents (41.12%) followed by the Solumbra technique without a BGC (32.4%). Among those using the Solumbra technique, 77.6% reported that they wait between 2 and 5 min to allow clot engagement, 55.2% always remove the microcatheter before aspiration, and 69.1% commence aspiration through the intermediate catheter only when retrieving the stent retriever. Operators who infrequently used or did not use BGCs reported a higher incidence of >80% Thrombolysis in Cerebral Infarction 2b/3 annual recanalization rates (OR 8.85, 95% CI 2.03 to 38.55, P=0.004) compared with those who consistently used BGCs.

Conclusion

Our study documents the variations in MT techniques, and more specifically, attempts to quantify variations in the Solumbra technique. The impact of these variations on recanalization rates and eventually patient outcomes are unclear, especially given the self-reported outcomes contained in this study.

Mechanical Thrombectomy: Emerging Technologies and Techniques

BACKGROUND

The treatment of acute ischemic stroke due to large vessel occlusion (LVO) has revolutionized in the last decade. We sought to compile the most relevant literature published about the evolution in treating this disabling and fatal disease.

METHODS

A literature review of recent studies describing early treatment options like intravenous tissue plasminogen activator to the latest mechanical thrombectomy (MT) techniques was performed. We described in a chronological order the evolution of LVO treatment.

RESULTS

Recanalization rates with newer techniques and MT devices approach a 90% of effectiveness. Timely interventions have also resulted in better clinical outcomes with approximately 50% of patient achieving functional independence at 90 days. At least 14 new third generation thrombectomy devices are currently being evaluated in in vitro and clinical studies.

CONCLUSIONS

The treatment of LVO with MT is feasible and safe. MT is standard of care in treating acute ischemic stroke due to LVO.

A Patient Dose-Reduction Technique for Neuroendovascular Image-Guided Interventions: Image-Quality Comparison Study

BACKGROUND AND PURPOSE

The ROI-dose-reduced intervention technique represents an extension of ROI fluoroscopy combining x-ray entrance skin dose reduction with spatially different recursive temporal filtering to reduce excessive image noise in the dose-reduced periphery in real-time. The aim of our study was to compare the image quality of simulated neurointerventions with regular and reduced radiation doses using a standard flat panel detector system.

MATERIALS AND METHODS

Ten 3D-printed intracranial aneurysm models were generated on the basis of a single patient vasculature derived from intracranial DSA and CTA. The incident dose to each model was reduced using a 0.7-mm-thick copper attenuator with a circular ROI hole (10-mm diameter) in the middle mounted inside the Infinix C-arm. Each model was treated twice with a primary coiling intervention using ROI-dose-reduced intervention and regular-dose intervention protocols. Eighty images acquired at various intervention stages were shown twice to 2 neurointerventionalists who independently scored imaging qualities (visibility of aneurysm-parent vessel morphology, associated vessels, and/or devices used). Dose-reduction measurements were performed using an ionization chamber.

RESULTS

A total integral dose reduction of 62% per frame was achieved. The mean scores for regular-dose intervention and ROI dose-reduced intervention images did not differ significantly, suggesting similar image quality. Overall intrarater agreement for all scored criteria was substantial (Kendall τ = 0.62887; P < .001). Overall interrater agreement for all criteria was fair (κ = 0.2816; 95% CI, 0.2060-0.3571).

CONCLUSIONS

Substantial dose reduction (62%) with a live peripheral image was achieved without compromising feature visibility during neuroendovascular interventions.

What to do about fibrin rich ‘tough clots’? Comparing the Solitaire stent retriever with a novel geometric clot extractor in an in vitro stroke model

Background

Despite advances in revascularization tools for large vessel occlusion presenting as acute ischemic stroke, a significant subset of clots remain recalcitrant to current strategies. We assessed the effectiveness of a novel thrombectomy device that was specifically designed to retrieve resistant fibrin rich clots, the geometric clot extractor (GCE; Neuravi, Galway, Ireland), in an in vitro cerebrovascular occlusion stroke model.

Methods

After introducing fibrin rich clot analogues into the middle cerebral artery of the model, we compared the rates of recanalization between GCE and Solitaire flow restoration stent retriever (SR; Medtronic, Minneapolis, Minnesota, USA; control group) cases. A maximum of three passes of each device was allowed. If the SR failed to recanalize the vessel after three passes, one pass of the GCE was allowed (rescue cases).

Results

In a total of 26 thrombectomy cases (13 GCE, 13 SR), successful recanalization (Thrombolysis in Cerebral Infarction score of 2b or 3) was achieved 100% of the time in the GCE cases with an average of 2.13 passes per case. This rate was significantly higher compared with the Solitaire recanalization rate (7.7%, P<0.0001) with an average of three passes per case. After SR failure (in 92% of cases), successful one pass GCE rescue recanalization was achieved 66% of the time (P<0.005).

Conclusion

Application of the GCE in this experimental stroke model to retrieve typically recalcitrant fibrin rich clots resulted in higher successful recanalization rates than the SR.

Mechanical thrombectomy in acute ischaemic stroke: a review of the different techniques

Endovascular mechanical thrombectomy (MT) is reserved for acute ischaemic stroke secondary to large vessel occlusion. The various MT techniques employed in the treatment of hyperacute strokes are constantly evolving with new devices and improvisation of existing technology (Wahlgren, et al 2016). In this review, we describe a variety of MT techniques gained from our experience of performing over 350 procedures in 7 years of providing a 24/7 service within the national framework of a hyperacute stroke centre. We outline a number of endovascular techniques, procedure limitations, and potential complications.

PROTECT: PRoximal balloon Occlusion TogEther with direCt Thrombus aspiration during stent retriever thrombectomy – evaluation of a double embolic protection approach in endovascular stroke treatment

Purpose

Stent retriever-based mechanical thrombectomy (MT) for emergent large vessel occlusions (ELVO) is often complicated by thrombus fragmentation causing distal embolization and embolization to new vascular territories. Well-established embolic protection approaches include proximal flow arrest and distal aspiration techniques during stent retriever maneuvers. Aiming at the reduction of thrombus fragmentation during MT we evaluated a technical approach combining proximal balloon occlusion together with direct thrombus aspiration during MT: the PROTECT technique.

Methods

We performed a case-control study comparing the PROTECT technique with sole distal aspiration during MT regarding technical and procedural parameters, n=200 patients with ELVO of either the terminus of the internal carotid artery or the proximal middle artery were included.

Results

PROTECT resulted in a shorter procedure time (29 vs 40 min; P=0.002), in a higher rate of successful recanalizations (100% vs 78%; P=0.001) and a higher rate of complete reperfusions (70% vs 39%; P<0.001) compared with sole distal aspiration during MT.

Conclusion

The PROTECT technique is a promising new approach to significantly reduce thrombus fragmentation and, hence distal embolization during MT. This safe and efficient technique needs to be validated in larger trials to confirm our results.

Impact of balloon guide catheter on technical and clinical outcomes: a systematic review and meta-analysis

Background and purpose

Flow arrest with balloon guide catheters (BGCs) is becoming increasingly recognized as critical to optimizing patient outcomes for mechanical thrombectomy. We performed a systematic review and meta-analysis of the literature for studies that compared angiographic and clinical outcomes for patients who underwent mechanical thrombectomy with and without BGCs.

Materials and methods

In April 2017 a literature search on BGC and mechanical thrombectomy for stroke was performed. All studies included patients treated with and without BGCs using modern techniques (ie, stent retrievers). Using random effects meta-analysis, we evaluated the following outcomes: first-pass recanalization, Thrombolysis In Cerebral Infarction (TICI) 3 recanalization, TICI 2b/3 recanalization, favorable outcome (modified Rankin Scale (mRS) 0–2), mortality, and mean number of passes and procedure time.

Results

Five non-randomized studies of 2022 patients were included (1083 BGC group and 939 non-BGC group). Compared with the non-BGC group, patients treated with BGCs had higher odds of first-pass recanalization (OR 2.05, 95% CI 1.65 to 2.55), TICI 3 (OR 2.13, 95% CI 1.43 to 3.17), TICI 2b/3 (OR 1.54, 95% CI 1.21 to 1.97), and mRS 0–2 (OR 1.84, 95% CI 1.52 to 2.22). BGC-treated patients also had lower odds of mortality (OR 0.52, 95% CI 0.37 to 0.73) compared with non-BGC patients. The mean number of passes was significantly lower for BGC-treated patients (weighted mean difference −0.34, 95% CI−0.47 to −0.22). Mean procedure time was also significantly shorter for BGC-treated patients (weighted mean difference −7.7 min, 95% CI−9.0to −6.4).

Conclusions

Non-randomized studies suggest that BGC use during mechanical thrombectomy for acute ischemic stroke is associated with superior clinical and angiographic outcomes. Further randomized trials are needed to confirm the results of this study.

Novel and emerging technologies for endovascular thrombectomy

Endovascular thrombectomy device improvements in recent years have served a pivotal role in improving the success and safety of the thrombectomy procedure. As the intervention gains widespread use, developers have focused on maximizing the reperfusion rates and reducing procedural complications associated with these devices. This has led to a boom in device development. This review will cover novel and emerging technologies developed for endovascular thrombectomy.

Initial Simulated FFR Investigation Using Flow Measurements in Patient-specific 3D Printed Coronary Phantoms

PURPOSE

Accurate patient-specific phantoms for device testing or endovascular treatment planning can be 3D printed. We expand the applicability of this approach for cardiovascular disease, in particular, for CT-geometry derived benchtop measurements of Fractional Flow Reserve, the reference standard for determination of significant individual coronary artery atherosclerotic lesions.

MATERIALS AND METHODS

Coronary CT Angiography (CTA) images during a single heartbeat were acquired with a 320×0.5mm detector row scanner (Toshiba Aquilion ONE). These coronary CTA images were used to create 4 patient-specific cardiovascular models with various grades of stenosis: severe, <75% (n=1); moderate, 50-70% (n=1); and mild, <50% (n=2). DICOM volumetric images were segmented using a 3D workstation (Vitrea, Vital Images); the output was used to generate STL files (using AutoDesk Meshmixer), and further processed to create 3D printable geometries for flow experiments. Multi-material printed models (Stratasys Connex3) were connected to a programmable pulsatile pump, and the pressure was measured proximal and distal to the stenosis using pressure transducers. Compliance chambers were used before and after the model to modulate the pressure wave. A flow sensor was used to ensure flow rates within physiological reported values.

RESULTS

3D model based FFR measurements correlated well with stenosis severity. FFR measurements for each stenosis grade were: 0.8 severe, 0.7 moderate and 0.88 mild.

CONCLUSIONS

3D printed models of patient-specific coronary arteries allows for accurate benchtop diagnosis of FFR. This approach can be used as a future diagnostic tool or for testing CT image-based FFR methods.

Thrombus Migration in the Middle Cerebral Artery: Incidence, Imaging Signs, and Impact on Success of Endovascular Thrombectomy

BACKGROUND

Thrombus migration (TM) in intracranial vessels during ischemic stroke has been reported in the form of case reports, but its incidence, impact on the technical success of subsequent endovascular thrombectomy and patients' outcome have never been studied systematically.

METHODS AND RESULTS

Retrospective analysis was done of 409 patients with isolated middle cerebral artery occlusions treated with endovascular thrombectomy. TM was observed (1) by analyzing discrepancies between computed tomographic angiography and digital subtraction angiography and (2) by comparing infarct pattern in the striatocapsular region with exact, angiographically assessed thrombus location within the M1-segment and the involvement of the middle cerebral artery perforators. Preinterventional infarction of discrepant regions (infarction in regions supplied by more proximal vessels than those occluded by the clot) was ensured by carefully reviewing available preinterventional multimodal imaging. Adequate imaging inclusion criteria were met by 325 patients. Ninety-seven patients showed signs of TM (26 with direct evidence, 71 with indirect evidence). There was no difference in the frequency of preinterventional intravenous recombinant tissue plasminogen activator administration between patients with TM and those without (63.9% vs 64.9%, P=0.899). TM was associated with lower rates of complete reperfusion (Thrombolysis in Cerebral Infarction score 3) (adjusted odds ratio 0.400, 95% CI 0.226-0.707). Subsequently, preinterventional TM was associated with lower rates of substantial neurologic improvement (adjusted odds ratio 0.541, 95% CI 0.309-0.946).

CONCLUSIONS

Preinterventional TM does not seem to be facilitated by intravenous recombinant tissue plasminogen activator and often occurs spontaneously. However, TM is associated with the risk of incomplete reperfusion in subsequent thrombectomy, suggesting increased clot fragility. Occurrence of TM may thereby have a substantial impact on the outcome of endovascularly treated stroke patients.

[Mechanical thrombectomy: Acute complications and delayed sequelae]

BACKGROUND

Due to the positive evidence for mechanical thrombectomy (mTE), it will be increasingly used in future. Profound knowledge of potential complications, prevention and management of complications is necessary to safely implement mTE into clinical practice.

AIM

Description of specific complications of mTE and their clinical relevance, measures for prevention and management. Summary of the current knowledge on long-term side effects of mTE.

MATERIAL AND METHODS

Analysis of current trial results and selected case series to address specific topics. Summary of own practical clinical experience.

RESULTS

Vascular injury (1-5%) and emboli (5-9%) are the most relevant intraprocedural complications but the clinical outcome is variable. Measures for prevention and management are described in detail. Vasospasms frequently occur (20-26%) but rarely need specific treatment and do not affect the clinical course. In the case of restrictive indications the frequency of symptomatic hemorrhage is similar to that for medicinal treatment (up to 8%). Contrast medium enhancement in the area of the infarction on post-treatment imaging should not be mistaken for hemorrhages. Focal subarachnoid contrast medium enhancement or hemorrhage occurs in up to 24% of cases and is predominantly benign. In follow-up imaging stenoses or occlusions can be detected in 4-10% of the treated vessels, most of which are asymptomatic. They are considered to be caused by microtrauma to the vascular wall.

CONCLUSION

Clinically relevant complications of mTE are rare. Preventive measures and effective management of complications may even increase safety. Stenoses occasionally occur as a long-term side effect but are asymptomatic in the majority of cases.

The use of stent retrievers in acute ischemic stroke

INTRODUCTION

Acute ischemic stroke (AIS) is one of the leading causes of mortality and adult disability worldwide. For two decades, the preferred approach for AIS was intravenous recombinant tissue plasminogen activator (IV tPA). However, IV tPA cannot be given to many AIS patients who do not meet strict criteria for its use. IV tPA has also had lesser benefit in patients with large clot burden in the context of large vessel occlusion (LVO).

AREAS COVERED

Endovascular stroke therapy had been an 'unproven' therapy despite numerous trials of intra-arterial pharmacologic thrombolysis and mechanical thrombectomy. With the advent of stent-retriever devices, there has been a paradigm shift in the utilization of endovascular therapies for AIS. Our review discusses cerebrovascular hemodynamics, the basis of the recanalization models in AIS, aspects of intravenous thrombolysis, prior generations of endovascular therapy, and the recent successful AIS stent retriever trials. Expert commentary: Recently 'stent-retrievers', a new generation of mechanical thrombectomy devices, were shown to be associated with improved functional outcomes in AIS secondary to proximal intracranial anterior circulation LVO. Stent retrievers are a major advance in AIS care and will have significant impact on the evolution of stroke systems of care.