In vitro experiments of cerebral blood flow during aspiration thrombectomy: potential effects on cerebral perfusion pressure and collateral flow

Flow reduction due to arterial catheterization during stroke treatment - A computational study using a distributed compartment model

The effectiveness of various stroke treatments depends on the anatomical variability of the cerebral vasculature, particularly the collateral blood vessel network. Collaterals at the level of the Circle of Willis and distal collaterals, such as the leptomeningeal arteries, serve as alternative avenues of flow when the primary pathway is obstructed during an ischemic stroke. Stroke treatment typically involves catheterization of the primary pathway, and the potential risk of further flow reduction to the affected brain area during this treatment has not been previously investigated. To address this clinical question, we derived the lumped parameters for catheterized blood vessels and implemented a corresponding distributed compartment (0D) model. This 0D model was validated against an experimental model and benchmark test cases solved using a 1D model. Additionally, we compared various off-center catheter trajectories modeled using a 3D solver to this 0D model. The differences between them were minimal, validating the simplifying assumption of the central catheter placement in the 0D model. The 0D model was then used to simulate blood flows in realistic cerebral arterial networks with different collateralization characteristics. Ischemic strokes were modeled by occlusion of the M1 segment of the middle cerebral artery in these networks. Catheters of different diameters were inserted up to the obstructed segment and flow alterations in the network were calculated. Results showed up to 45% maximum blood flow reduction in the affected brain region. These findings suggest that catheterization during stroke treatment may have a further detrimental effect for some patients with poor collateralization.

Collateral flow and pulsatility during large vessel occlusions: insights from a quantitative in vitro study

Acute ischemic stroke caused by large vessel occlusions is being increasingly treated with neurovascular interventions. The hemodynamics within the collateral system of the circle of Willis (CoW) hemodynamics play a fundamental role in therapy success. However, transient in vivo data on pathological collateral flow during large vessel occlusions are not available. Moreover, there are no flow models that accurately simulate the hemodynamic conditions in the CoW during large vessel occlusions. We used a circulatory loop to generate highly reproducible cerebrovascular-like flows and pressures and used non-invasive flow visualization and high-resolution flow and pressure measurements to acquire detailed, time-dependent hemodynamics inside an anatomical phantom of the CoW. After calibrating a physiological reference case, we induced occlusions in the 1. middle cerebral artery, 2. terminal carotid artery, and 3. basilar artery; and measured the left posterior communicating artery flow. Mean arterial pressure and pulse pressure remained unchanged in the different occlusion cases compared to the physiological reference case, while total cerebral flow decreased by up to 19%. In all three occlusion cases, reversed flow was found in the left posterior communicating artery compared to the reference case with different flow magnitudes and pulsatility index values. The experimental results were compared with clinical findings, demonstrating the capability of this realistic cerebrovascular flow setup. This novel cerebrovascular flow setup opens the possibility for investigating different topics of neurovascular interventions under various clinical conditions in controlled preclinical laboratory studies.

A one-dimensional computational model for blood flow in an elastic blood vessel with a rigid catheter

Strokes are one of the leading causes of death in the United States. Stroke treatment involves removal or dissolution of the obstruction (usually a clot) in the blocked artery by catheter insertion. A computer simulation to systematically plan such patient-specific treatments needs a network of about 105 blood vessels including collaterals. The existing computational fluid dynamic (CFD) solvers are not employed for stroke treatment planning as they are incapable of providing solutions for such big arterial trees in a reasonable amount of time. This work presents a novel one-dimensional mathematical formulation for blood flow modeling in an elastic blood vessel with a centrally placed rigid catheter. The governing equations are first-order hyperbolic partial differential equations, and the hypergeometric function needs to be computed to obtain the characteristic system of these hyperbolic equations. We employed the Discontinuous Galerkin method to solve the hyperbolic system and validated the implementation by comparing it against a well-established 3D CFD solver using idealized vessels and a realistic truncated arterial network. The results showed clinically insignificant differences in steady flow cases, with overall variations between 1D and 3D models remaining below 10%. Additionally, the solver accurately captured wave reflection phenomena at domain discontinuities in unsteady cases. A primary advantage of this model over 3D solvers is its ease in obtaining a discretized geometry of complex vasculatures with multiple arterial branches. Thus, the 1D computational model offers good accuracy and applicability in simulating complex vasculatures, demonstrating promising potential for investigating patient-specific endovascular interventions in strokes.

Current Approaches and Methods to Understand Acute Ischemic Stroke Treatment Using Aspiration Thrombectomy

Acute ischemic stroke occurs when a blood clot occludes a cerebral artery. Mechanical interventions, primarily stent retrievers and aspiration thrombectomy, are used currently for removing the occluding clot and restoring blood flow. Aspiration involves using a long catheter to traverse the cerebral vasculature to reach the blood clot, followed by application of suction through the catheter bore. Aspiration is also used in conjunction with other techniques such as stent retrievers and balloon guide catheters. Despite the wide use of aspiration, our physical understanding of the process and the causes of the failure of aspiration to retrieve cerebral clots in certain scenarios is not well understood. Experimental and computational studies can help develop the capability to provide deeper insights into the procedure and enable development of new devices and more effective treatment methods. We recapitulate the aspiration-based thrombectomy techniques in clinical practice and provide a perspective of existing engineering methods for aspiration. We articulate the current knowledge gap in the understanding of aspiration and highlight possible directions for future engineering studies to bridge this gap, help clinical translation of engineering studies, and develop new patient-specific stroke therapy.

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.

The effect of distal aspiration catheter position on collateral flow in mechanical thrombectomy - an in vitro study

INTRODUCTION

Endovascular mechanical thrombectomy for ischaemic stroke is one of the most effective treatments. Despite the devices and techniques that have been developed, thrombi are not always successfully retrieved. The incidence of futile reperfusion after successful clot retrieval also remains a major concern. We hypothesise that simply placing an aspiration catheter in the system compromises collateral flow which may have an impact on functional outcomes.

METHODS

An in vitro study was conducted using a physical pulsatile flow model designed in glass to mimic the anterior cerebral circulation with middle cerebral artery M1 segment occlusion. A 5Fr aspiration catheter was positioned at the supra-clinoid internal carotid (SC-ICA), carotid terminus (T-ICA) and M1. For each catheter position, the flow rate through the model's anterior cerebral (ACA) and posterior communicating (PCOM) arteries was measured (no aspiration applied).

RESULTS

Our results showed significant mean percentage flow reductions in the ACA and PCOM with the catheter positioned at the SC-ICA (PCOM 59.14% ± 0.93, ACA 59.52% ± 0.82, p < 0.001), T-ICA (PCOM 81.54% ± 0.55, ACA 85.65% ± 1.54) and M1 (PCOM 75.79% ± 0.98, ACA 84.20% ± 0.43) (Mann-Whitney U Test, p < 0.001).

CONCLUSION

These results indicate a significant reduction in collateral flow following the insertion of a wide bore catheter in an in vitro model. In a clinical setting, this could have an impact on patient outcome, particularly in prolonged procedures and those requiring several passes to achieve recanalisation.

Investigation of Cerebral Hemodynamics During Endovascular Aspiration: Development of an Experimental and Numerical Setup

PURPOSE

Acute ischemic stroke is a life-threatening emergency caused by an occlusion of a cerebral artery through a blood clot. Aspiration thrombectomy is an endovascular therapy for the removal of vessel occlusions. However, open questions regarding the hemodynamics during the intervention remain, motivating investigations of blood flow within cerebral arteries. In this study, we present a combined experimental and numerical approach to analyze hemodynamics during endovascular aspiration.

METHODS

We have developed an in vitro setup for investigations of hemodynamic changes during endovascular aspiration within a compliant model of patient-specific cerebral arteries. Pressures, flows, and locally resolved velocities were obtained. In addition, we established a computational fluid dynamics (CFD) model and compared the simulations during physiological conditions and in two aspiration scenarios with different occlusions.

RESULTS

Flow redistribution within cerebral arteries after ischemic stroke is strongly dependent on the severity of the occlusion and on the volume flow extracted by endovascular aspiration. Numerical simulations exhibit an excellent correlation of R = 0.92 for flow rates and a good correlation of R = 0.73 for pressures. Further on, the local velocity field inside the basilar artery had a good agreement between CFD model and particle image velocimetry (PIV) data.

CONCLUSION

The presented setup allows for in vitro investigations of artery occlusions and endovascular aspiration techniques on arbitrary patient-specific cerebrovascular anatomies. The in silico model provides consistent predictions of flows and pressures in several aspiration scenarios.

A multiscale computational framework to evaluate flow alterations during mechanical thrombectomy for treatment of ischaemic stroke

The treatment of ischaemic stroke increasingly relies upon endovascular procedures known as mechanical thrombectomy (MT), which consists in capturing and removing the clot with a catheter-guided stent while at the same time applying external aspiration with the aim of reducing haemodynamic loads during retrieval. However, uniform consensus on procedural parameters such as the use of balloon guide catheters (BGC) to provide proximal flow control, or the position of the aspiration catheter is still lacking. Ultimately the decision is left to the clinician performing the operation, and it is difficult to predict how these treatment options might influence clinical outcome. In this study we present a multiscale computational framework to simulate MT procedures. The developed framework can provide quantitative assessment of clinically relevant quantities such as flow in the retrieval path and can be used to find the optimal procedural parameters that are most likely to result in a favorable clinical outcome. The results show the advantage of using BGC during MT and indicate small differences between positioning the aspiration catheter in proximal or distal locations. The framework has significant potential for future expansions and applications to other surgical treatments.

In vitro evaluation of how the presence of the stent retriever and microcatheter influences aspiration parameters in thrombectomy according to their position inside the aspiration catheter

BACKGROUND

Several variations of the combined thrombectomy technique for acute ischemic stroke using a stent retriever and aspiration catheter have been described. The aim of our study was to assess how the presence of the microcatheter and stent retriever affect the basic aspiration parameters, namely, flow rate and aspiration force, depending on their position within the aspiration catheter.

METHODS

Two experimental set-ups were designed to assess changes in flow rate and aspiration force according to the position of the stent retriever and microcatheter within the aspiration catheter.

RESULTS

The transition of the stent retriever and microcatheter from the distal to proximal position resulted in a progressive increase in the flow rate, but with no impact on aspiration force. Additionally, the size of the stent retriever had no significant effect on flow rate changes and the reduction in flow rate was related to the microcatheter diameter. Negative pressure generated inside the aspiration catheter impacted on its distal segment located beyond the radiopaque marker, thus leading to its partial collapse. As a consequence, the measured aspiration force was lower than the theoretical aspiration force level for all tested aspiration catheters.

CONCLUSIONS

In our experimental model, the position of the stent retriever and microcatheter within the aspirator catheter affected the flow rate, but not the aspiration force. Negative pressure generated within the aspiration catheter appeared to determine a partial collapse of the distal segment that resulted in a less effective aspiration force than the theoretical aspiration force level.

Comparison of vacuum pressures and suction forces generated by different pump systems for aspiration thrombectomy

Objective

Aspiration thrombectomy is used to treat endovascular stroke treatment by clot removal through vacuum and suction forces. We aimed to investigate the pressures and suction forces generated by different pump systems for aspiration.

Methods

Vacuum pressure was measured using a vacuum gauge with a closed tip for a 60cc syringe and aspiration pumps. Using an artificial thrombus made from polyvinyl alcohol hydrogel and latex membrane, we assessed the catheter tip force generated on an artificial thrombus using 5Fr Sofia and 6Fr Sofia PLUS intermediate catheters combined with Penumbra Jet Engine or Stryker Medela AXS Universal Aspiration Set. Subsequently, we calculated the catheter tip forces based on the pressure [catheter tip size (force = area × pressure)], and compared with the measured catheter tip force.

Results

The 60cc syringe generated the highest vacuum pressure. Among the automatic pumps, the Penumbra jet engine generated the highest vacuum pressure. The catheter tip forces on the artificial thrombus and latex membrane were 18.5 ± 1.70 and 8.0 ± 1.23 gf, respectively, and 13.9 ± 1.37 and 5.6 ± 0.83 gf, respectively using the 5 Fr Sofia with the Penumbra Jet Engine and the Stryker Medela AXS Universal Aspiration Set, respectively. The corresponding values for the 6 Fr Sofia PLUS with the Penumbra Jet Engine and Stryker Medela AXS Universal Aspiration Set were 39.7 ± 3.88 and 20.7 ± 0.92 gf and 25.4 ± 4.96 and 18.0 ± 0.84 gf. For a constant catheter diameter and the automatic pump, the catheter tip force was significantly larger in the artificial thrombus than latex membrane (p < 0.001, ANOVA).

Conclusion

The catheter diameter, vacuum pressure, and clot softness are positively correlated with the catheter tip force.

Flow control in the middle cerebral artery during thrombectomy: the effect of anatomy, catheter size and tip location

BACKGROUND

Catheter size, location and circle of Willis anatomy impact the flow conditions during interventional stroke therapy. The aim of the study was to systematically investigate the influence of these factors on flow control in the middle cerebral artery by means of a computational model based on 100 patients with stroke who received endovascular treatment.

METHODS

The dimensions of the cervical and intracranial cerebral arteries of 100 patients who received endovascular mechanical thrombectomy for acute ischemic stroke were measured and a three-dimensional model of the circle of Willis was created based on these data. Flow control in the middle cerebral artery with variations in catheter size, catheter location and configurations of collateral vessels was determined using a computational model. A total of 48 scenarios were analyzed.

RESULTS

Flow reversal with a distal aspiration catheter alone was not possible in the internal carotid artery and only sometimes possible in the middle cerebral artery (14 of 48 cases). The Catalyst 7 catheter was more often successful in achieving flow reversal than Catalyst 5 or 6 catheters (p<0.001). In a full circle of Willis anatomy, flow reversal was almost never possible. The absence of one or more communicating arteries significantly influenced flow direction compared with the full anatomy with all communicating arteries present (p=0.028).

CONCLUSION

Choosing the biggest possible aspiration catheter and locating it in the middle cerebral artery significantly increases the chances of successful flow control. Flow through the collaterals may impair the flow, and circle of Willis anatomy should be considered during aspiration thrombectomy.

In vitro and in silico modeling of endovascular stroke treatments for acute ischemic stroke

Acute ischemic stroke occurs when a thrombus obstructs a cerebral artery, leading to sub-optimal blood perfusion to brain tissue. A recently developed, preventive treatment is the endovascular stroke treatment (EVT), which is a minimally invasive procedure, involving the use of stent-retrievers and/or aspiration catheters. Despite its increasing use, many critical factors of EVT are not well understood. In this respect, in vitro, and in silico studies have the great potential to help us deepen our understanding of the procedure, perform further device and procedural optimization, and help in clinical training. This review paper provides an overview of the previous in vitro and in silico evaluations of EVT treatments, with a special emphasis on the four main aspects of the adopted experimental and numerical set-ups: vessel, thrombus, device, and procedural settings.

Catheter tip distensibility substantially influences the aspiration force of thrombectomy devices

BACKGROUND

A direct aspiration first pass thrombectomy (ADAPT) is a fast-growing technique for which a broad catalog of catheters that provide a wide range of aspiration forces can be used. We aimed to characterize different catheters' aspiration performance on stiff clots in an in vitro vascular model. We hypothesized that labeled catheter inner diameter (labeled-ID) is not the only parameter that affects the aspiration force (asp-F) and that thrombus-catheter tip interaction and distensibility also play a major role.

METHODS

We designed an experimental setup consisting of a 3D-printed carotid artery immersed in a water deposit. We measured asp-F and distensibility of catheter tips when performing ADAPT on a stiff clot analog larger than catheter labeled-ID. Correlations between asp-F, catheter ID, and tip distensibility were statistically assessed.

RESULTS

Experimental asp-F and catheter labeled-ID were correlated (r=0.9601; P<0.01). The relative difference between experimental and theoretical asp-F (obtained by the product of the tip's section area by the vacuum pressure) correlated with tip's distensibility (r=0.9050; P<0.01), evidencing that ADAPT performance is highly influenced by catheter tip shape-adaptability to the clot and that the effective ID (eff-ID) may differ from the labeled-ID specified by manufacturers. Eff-ID showed the highest correlation with experimental asp-F (r=0.9944; P<0.01), confirming that eff-ID rather than labeled-ID should be considered to better estimate the device efficiency.

CONCLUSIONS

Catheter tip distensibility can induce a significant impact on ADAPT performance when retrieving a stiff clot larger than the device ID. Our findings might contribute to optimizing thrombectomy strategies and the design of novel aspiration catheters.

Preliminary experience with 088 large bore intracranial catheters during stroke thrombectomy

BACKGROUND AND PURPOSE

Thromboaspiration technology continues to evolve at an accelerated pace with increasing availability of larger and more navigable devices. Herein, we provide our initial experience with the intracranial navigation of a large-bore (.088" inner diameter) catheters during mechanical thrombectomy (MT).

METHODS

Retrospective review of consecutive large vessel occlusion stroke patients in whom a TracStar™ or Zoom 88™ (Imperative Care, Campbell, CA) large-bore catheters were utilized in MT. The primary outcome was successful reperfusion (eTICI2b-3) at the end of the procedure. Safety measures included procedural complications and rates of symptomatic intracranial hemorrhage.

RESULTS

Five patients (age,∼50-85 years; baseline NIHSS,17-23) were treated. The .088" catheters were used as the primary tool for contact aspiration in two patients (distal basilar artery and proximal MCA occlusions) with complete thrombus ingestion (eTICI3) during the first pass. In two patients, the .088" catheter was used for flow control where it was placed in the distal M1-segment of a patient with M2 occlusion treated with a combination of stent-retriever and .070" aspiration catheter and in the proximal M1 in a patient with distal M1 occlusion treated with .071" aspiration catheter resulting in eTICI3 reperfusion in both cases. In the fifth patient, the .088" catheter was navigated into the cavernous ICA to support .071" aspiration catheter treatment of an M2 occlusion resulting in eTCI2b67 reperfusion. Procedural duration ranged between 14 and 33 minutes. There were no adverse events.

CONCLUSION

Intracranial navigation of .088" large-bore catheters in MT appears technically feasible and safe. Larger prospective studies are warranted.

Mechanical Thrombectomy using Distal Access Catheters: Current Status and Future Prospects

BACKGROUND AND PURPOSE

Mechanical Thrombectomy (MT) using modern devices has proved to be efficacious in re-establishing intracranial circulation and reduced procedural times. We outline a number of endovascular techniques utilizing the distal access catheter, the circumstances where they are applicable, and the outcomes achieved.

METHODS

In this review, we describe a variety of endovascular techniques with distal access catheter, deployed with and without the stent retriever device gained from our experience of performing over 700 procedures in 10 years of providing a 24/7 service within the national framework of a hyperacute stroke centre.

RESULTS

We used distal access catheter techniques for intracranial support during a stent-retriever thrombectomy or thrombo-suction on its own. When used as a sole suction device, or combined with a stent-retriever, we have been able to provide a rapid route to successful reperfusion, with minimal complications related to our endovascular procedures. We can report distal access catheter techniques works well when access to thrombi involves navigation through tortuous vessel anatomy, notably when convoluted loops in the cervical internal carotid artery are encountered. We suggest use of the distal access catheter techniques in thrombectomy procedures for steep-angle Middle Cerebral Artery occlusions, M2/M3 occlusion, and for basilar occlusion, where thrombectomy via suction alone proved to be adequate.

CONCLUSION

In this pictorial review, we have demonstrated techniques where distal access catheter when used as a sole suction device, or combined with a stent-retriever, has been able to provide a rapid route to successful reperfusion, with minimal complications related to our endovascular procedures.

In vitro Remote Aspiration Embolectomy for the Treatment of Acute Ischemic Stroke

Background

"Remote aspiration," using suction from the proximal internal carotid artery (ICA) to open terminus occlusions, has been reported in small case series. However, it remains unclear whether remote aspiration is feasible for middle cerebral artery occlusions in the setting of potential inflow from communicating arteries. We performed an in vitro study to assess whether suction applied at various locations proximal to an occlusion could successfully aspirate the clot.

Methods

A glass model of 4 mm inner diameter (ID) with 1 mm distal narrowing and 2 mm side branch to simulate a communicating artery was constructed. A proximal side branch was placed to simulate inflow from the proximal ICA. The impact of three different-sized catheters (ID 0.088, 0.070, and 0.056 in) on histologically different (red blood cell-cell rich, fibrin-rich, and mixed) clot analogues was tested with the catheter tip placed remotely either distal or proximal to the collateral branch. Aspiration was attempted with (1) open system (flow in both the ICA and the collateral branch, (2) flow arrest with open collateral (no flow in the ICA, but flow in the collateral branch), and (3) closed system (no flow in either the ICA or the collateral branch). The outcome was success or failure of remote aspiration.

Results

For the 0.088-in catheter, remote aspiration was successful in all conditions. For the 0.070-in catheter, remote aspiration was unsuccessful without proximal flow arrest, but was successful in all other scenarios. For the 0.056-in catheter, remote aspiration was successful only with complete flow arrest.

Conclusions

In a noncollapsible system, remote aspiration can be successfully achieved even in the setting of prominent branch arteries by using relatively large aspiration catheters. Proximal flow arrest may facilitate successful remote aspiration for some catheter sizes.

A technical comparison of thrombectomy vacuum aspiration systems

INTRODUCTION

Improved functional outcomes after mechanical thrombectomy for emergent large vessel occlusion depend on expedient reperfusion after clinical presentation. Device technology has improved substantially over the years, and several commercial options exist for both large-bore aspiration catheters and suction pump systems.

OBJECTIVE

To compare various vacuum pumps and examine the aspiration forces they generate as well as the force of catheter tip detachment from an artificial thrombus.

METHODS

Using an artificial thrombus made from polyvinyl alcohol gel, we tested various mechanical characteristics of commercially available suction pumps, including the Penumbra Jet Engine, Penumbra Max, Stryker Medela AXS, Microvention Gomco, and a 60 cc syringe. Both aspiration pressure and tip force generated were analyzed. Subsequently, a cohort of thrombectomy catheters were assessed using the Penumbra Jet Engine to determine tip forces generated on an artificial thrombus. One-way analysis of variance was used to assess statistical significance.

RESULTS

The Penumbra Jet Engine system generated both the highest maximum aspiration pressures (28.8 inches Hg) and the highest tip force (23.68 grams force (gf)) on an artificial thrombus, with statistical significance compared with the other pump systems. Using the Jet Engine, the largest-bore catheter was associated with the highest tip force (32.12 gf). The overall correlation coefficient between catheter inner diameter and tip force was 0.98.

CONCLUSIONS

The Penumbra Jet Engine pump generates significantly higher vacuum pressures and tip forces than the other commercially available aspiration pump systems. Furthermore, catheters with a larger inner diameter generate higher tip suction forces on aspiration. Whether these mechanical features lead to improved clinical outcomes is yet to be determined.

ANCD thrombectomy device: in vitro evaluation

Introduction

Endovascular treatment of stroke, although highly effective, may fail to reach complete recanalization in around 20% of cases. The Advanced Thrombectomy System (ANCD) is a novel stroke thrombectomy device designed to reduce clot fragmentation and facilitate retrieval by inducing local flow arrest and allowing distal aspiration in combination with a stent retriever. We aimed to assess the preclinical efficacy of ANCD.

Methods

Soft red blood cell (RBC)-rich (n=20/group) and sticky fibrin-rich (n=30/group) clots were used to create middle cerebral artery (MCA) occlusions in two vascular phantoms. Three different treatment strategies were tested: (1) balloon guide catheter + Solitaire (BGC+SR); (2) distal access catheter + SR (DAC+SR); and (3) ANCD+SR, until complete recanalization was achieved or to a maximum of three passes. The recanalization rate was determined after each pass.

Results

After one pass, ANCD+SR resulted in an increased recanalization rate (94%) for all clots together compared with BGC+SR (66%; p<0.01) or DAC+SR (80%; p=0.04). After the final pass the recanalization rate increased in all three groups but remained higher with ANCD+SR (100%) than with BGC+SR (74%; p<0.01) or DAC+SR (90%; p=0.02). The mean number of passes was lower with ANCD+SR (1.06) than with BGC+SR (1.46) or DAC+SR (1.25) (p=0.01). A logistic regression model adjusted for treatment arm, clot type, and model used showed that both RBC-rich clots (OR 8.1, 95% CI 1.6 to 13.5) and ANCD+SR (OR 3.9, 95% CI 1.01 to 15.8) were independent predictors of first-pass recanalization.

Conclusion

In in vitro three-dimensional models replicating MCA-M1 occlusion, ANCD+SR showed significantly better recanalization rates in fewer passes than other commonly used combinations of devices.

Balloon-Guide Catheters Are Needed for Effective Flow Reversal during Mechanical Thrombectomy

BACKGROUND AND PURPOSE

Blood flow management in the carotid artery during mechanical thrombectomy is crucial for safety and effectiveness. There is an ongoing discussion about whether balloon-guide catheters or large-bore sheaths are needed for effective flow management. We compared general flow characteristics of proximal aspiration through a large-bore sheath and a balloon-guide catheter in a porcine in vivo model.

MATERIALS AND METHODS

We investigated blood flow in a porcine common carotid artery with and without aspiration (VacLok syringe and Penumbra pump, Pump MAX) through an 8F-long sheath and an 8F balloon-guide catheter. Blood hemodynamics were assessed via continuous duplex sonography.

RESULTS

Average vessel diameter and baseline blood flow were 4.4 ± 0.2 mm and 244 ± 20 mL/min, respectively. For the 8F sheath, pump aspiration resulted in a significant flow reduction (225 ± 25 mL/min, P < .001), but with a persisting antegrade stream. Manual aspiration resulted in collapse of the vessel in 2 of 7 measurements and oscillatory flow with antegrade systolic and retrograde diastolic components in the remaining 5 measurements. Net flow was antegrade (52 ± 44 mL/min) in 3 and retrograde (-95 ± 52 mL/min) in the remaining 2 measurements. For balloon-guide catheters, balloon inflation always resulted in flow arrest. Additional pump or manual aspiration resulted in significant flow reversal of -1100 ± 230 and -468 ± 46 mL/min, respectively (both, P < .001).

CONCLUSIONS

Only balloon-guide catheters allow reliable blood flow arrest and flow reversal in combination with aspiration via syringes or high-flow pump systems. Aspiration through an 8F sheath results in either collapse of the vessel or oscillatory flow, which can result in a net antegrade or retrograde stream.