Introduction: Recent reports have raised concern about the risk of vessel wall injury (VWI) when pulling out current laser-cut stent retrievers during active strut apposition to the vessel walls.1-4 Development of braided thrombectomy-assist devices for use in conjunction with aspiration systems may be gentler (lower radial force) and more optimized for vessel diameters seen in proximal LVOs and distal LVOs.
Methods: Bench testing of radial force (RF) was performed using a radial compression station. The total radial force (RF) in Newtons (N) generated in vessel diameters (d) (Range 2.25 to 3mm) seen in proximal LVOs (~M1), and vessel diameters (d) (Range 1.5 to 2.24mm) seen in distal LVOs (~M2) was measured. Radial Force of less than or equal to 1N was grouped as “low” and radial force greater than 1N was grouped as “high” for this analysis.
Results:
The total radial force (RF) of all laser-cut stent retrievers (with distal outer diameter OD in mm) studied namely Solitaire Platinum (6.0), Solitaire 2 (4.0), Trevo ProVue (4.0), Baby Trevo (3.0), Capture L (3.0) were all higher in the M2 vessels (>1N) compared to M1 vessels (<1N), whereas the total radial force (RF) of the braided thrombectomy-assist devices namely SHELTER® Retriever (6.0) were uniformly low in both the M1 (<1N) and M2 (<1N) vessels.
Conclusion:
Choosing a stent retriever with lower OD does not translate to lower radial force. As a result, sizing of stent retrievers and thrombectomy-assist devices to target vessels should not only factor the OD of the devices but also the total radial force in the target vessel diameter.
Novel braided thrombectomy-assist devices for use in conjunction with aspiration systems have lower radial force compared to existing laser-cut stent retrievers in the M1 and M2 vessel diameters. Further studies in-vivo need to assess the impact of lower radial force on minimizing VWI.
Funding Source: This study was funded in part by a research grant (NSF Award: 1819491; PI: Vallabh Janardhan, MD) from the National Science Foundation (NSF). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.
Conference Proceeding: This paper was presented in part at the 2018 Annual Meeting of the Society of Vascular & Interventional Neurology (SVIN), November 14-17, 2018 in San Diego, CA
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Radial Force of Braided Thrombectomy-Assist Devices Vis-à-Vis Laser-cut Stent Retrievers in the ICA and Basilar.
Background: Recent reports have raised concern about the risk of vessel wall injury (VWI) when pulling out current laser-cut stent retrievers with active strut apposition to the vessel walls. Development of braided stroke thrombectomy-assist devices for use in conjunction with aspiration systems may be gentler in the internal carotid (ICA) and basilar vessels (with regards to radial force) compared to existing laser-cut stent retrievers.
Methods: Radial force (RF) bench testing was performed using a radial compression station (Blockwise Engineering, Phoenix, AZ). The average total radial force (RF) in Newtons (N) generated (average of 3 readings) in vessel diameters (d) (Range 3.25 to 4.00mm) seen in proximal LVOs of the anterior circulation (such as in the internal carotid artery - ICA), and vessel diameters (d) (Range 2.50 to 3.25mm) seen in the posterior circulation (such as in the basilar artery - BA) was measured. The Solitaire Platinum Revascularization Device (Medtronic, Irvine, CA) was used as the predicate device. All thrombectomy and thrombectomy-assist devices were compared in terms of the RF being higher or lower (%) to the predicate device.
Results: The results of the radial force testing are shown in the table below. The total radial force (RF) of the SHELTER® Retriever (part of Insera System, Insera Therapeutics, Inc., Dallas, TX), a braided thrombectomy-assist device is significantly lower (@ d=2.5mm: 58%) than the predicate device (@ d=2.5mm: 100%) and other laser-cut stent retrievers (@ d=2.5mm: 103% to 152%). Thrombectomy devices with lower OD had higher radial forces than larger devices.
Conclusion: Novel braided stroke thrombectomy-assist devices for use in conjunction with aspiration systems have lower radial force compared to existing laser-cut stent retrievers in the ICA and BA vessel diameters. Further studies in-vivo need to assess the impact of lower radial force on minimizing VWI.
Funding Source: This study was funded in part by a research grant (NSF Award: 1819491; PI: Vallabh Janardhan, MD) from the National Science Foundation (NSF). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.
Conference Proceeding: This paper was presented in part at the 2018 Annual Meeting of the Society of Vascular & Interventional Neurology (SVIN), November 14-17, 2018 in San Diego, CA
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- Award ID(s):
- 1819491
- NSF-PAR ID:
- 10132848
- Date Published:
- Journal Name:
- Society of Vascular & Interventional Neurology (SVIN)
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Purpose: Recent reports have raised various concerns about the risk of vessel wall injury while withdrawing current laser-cut stent retrievers during active strut apposition to the vessel walls. The development of braided thrombectomy assist devices in conjunction with aspiration systems may be gentler on the fragile brain vessels and more optimized with regard to the radial force (RF) for vessel diameters of proximal (M1) and distal (M2) large vessel occlusions (LVOs). Methods: Mechanical bench testing of the RF was performed using a radial compression station mounted on a tensile testing machine. The total RF in newtons (N) generated in vessels with diameters ranging from 2.25 to 3 mm as seen in proximal LVOs (∼M1), and in vessel diameters ranging from 1.5 to 2.24 mm as seen in distal LVOs (∼M2), was measured. The outer diameter of each stent was recorded, and an RF ≤1 N was grouped as “low,” while an RF > 1 N was grouped as “high” for this analysis. Results: The total RFs of all laser-cut stent retrievers were all higher in the simulated M2 vessels (> 1 N) than in the M1 vessels (< 1 N), whereas the total RFs of the braided thrombectomy assist devices were uniformly low in both the simulated M1 and the simulated M2 vessels. Conclusions: Novel braided thrombectomy assist devices in conjunction with aspiration systems have lower RFs than existing laser-cut stent retrievers in M1 and M2 vessel diameters. Further in vivo studies are needed to delineate the impact of lowering the RF on vessel wall integrity. Funding Source: This study was funded in part by a research grant (NSF Award: 1819491; PI: Vallabh Janardhan, MD) from the National Science Foundation (NSF). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. Conference Proceeding: This paper was presented in part at the 15th Annual Meeting of the Society of Neuro-Interventional Surgery (SNIS), July 23-26, 2018 in San Francisco, CA.more » « less
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Background: Aspiration is an important part of stroke thrombectomy (1). Pre-clinical studies have also suggested that uniform aspiration may need to be customized for varying vessel diameters and that cyclical (varying suction intensity) aspiration may be more effective (2). Methods: Suction intensity and duration are customized in an iPad app to create uniform aspiration (using the CLEAR TM App, Insera Therapeutics) or cyclical (using the CLEAR Pro TM App, Insera Therapeutics) aspiration. Customized aspiration initiated via the iPad app activates a Bluetooth-enabled smart pump (CLEAR Aspiration System TM, Insera Therapeutics) connected to a standard aspiration catheter with an inner diameter (ID) of 0.070" and length of 131 cm was studied. The suction intensity at the catheter tip is confirmed using a vacuum gauge (DuraChoice) and a previously defined technique (3), and any catheter luminal collapse is noted in an in-vitro flow model (United Biologics) simulating stroke thrombectomy. Results: Activating the smart pump to generate customized uniform and cyclical aspiration (suction range 0 to -29 in Hg) using an iPad app was successful. A vacuum gauge at the catheter tip confirmed the varying suction intensities generated by the smart pump without any catheter lumen collapse. Low, medium and high suction intensities of -13, -21, and -29 inHg on the digital smart pump resulted in a suction intensities at the catheter tip of -12.5, -20.5, and -28.5 inHg. Pause of 0 inHg on the digital smart pump resulted in similar intensity at catheter tip. There was similar transmission of suction intensities between the digital smart pump and the catheter tip for uniform and cyclical aspiration patterns. Conclusion: It is feasible to customize uniform and cyclical aspiration using a digital smart pump. Further studies need to evaluate the impact of customizing uniform and cyclical aspiration on varying vessel diameters, clot types, and clot burden. Funding Source: This study was funded in part by a research grant (NSF Award: 1819491; PI: Vallabh Janardhan, MD) from the National Science Foundation (NSF). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. Conference Proceeding: This paper was presented in part at the 2018 Annual Meeting of the Society of Vascular & Interventional Neurology (SVIN), November 14-17, 2018 in San Diego, CAmore » « less
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Background Carotid webs (CaWs) are fibromuscular projections in the internal carotid artery (ICA) that cause mild luminal narrowing (<50%), but may be causative in up to one‐third of seemingly cryptogenic strokes. Understanding hemodynamic alterations caused by CaWs is imperative to assessing stroke risk. Time‐Average Wall Shear Stress (TAWSS) and Oscillatory Shear Index (OSI) are hemodynamic parameters linked to vascular dysfunction and thrombosis.
Purpose To test the hypothesis: “CaWs are associated with lower TAWSS and higher OSI than mild atherosclerosis or healthy carotid bifurcation.”
Study Type Prospective study.
Population A total of 35 subjects (N = 14 bifurcations with CaW, 11F, age: 49 ± 10, 10 mild atherosclerosis 6F, age: 72 ± 9, 11 healthy 9F, age: 42 ± 13).
Field Strength/Sequence 4D flow/STAR‐MATCH/3D TOF/3T MRI, CTA.
Assessment 4D Flow velocity data were analyzed in two ways: 1) 3D ROI in the ICA bulbar segment (complex flow patterns are expected) was used to quantify the regions with low TAWSS and high OSI. 2) 2D planes were placed perpendicular to the centerline of the carotid bifurcation for detailed analysis of TAWSS and OSI.
Statistical Tests Independent‐samples Kruskal–Wallis‐H test with 0.05 used for statistical significance.
Results The percent surface area where low TAWSS was present in the ICA bulb was 12.3 ± 8.0% (95% CI: 7.6–16.9) in CaW subjects, 1.6 ± 1.9% (95% CI: 0.2–2.9) in atherosclerosis, and 8.5 ± 7.7% (95% CI: 3.6–13.4) in healthy subjects, all differences were statistically significant (
ƞ 2 = 0.3 [95% CI: 0.05–0.5],P ‐value CaW vs. healthy = 0.2). OSI had similar values in the CCA between groups (ƞ 2 = 0.07 [95% CI: 0.0–0.2],P ‐value = 0.5), but OSI was significantly higher downstream of the bifurcation in CaW subjects compared to atherosclerosis and normal subjects. OSI returned to similar values between groups 1.5 diameters distal to the bifurcation (ƞ 2 = 0.03 [95% CI: 0.0–0.2],P ‐value = 0.7).Conclusion Lower TAWSS and higher OSI are present in the ICA bulb in patients with CaW when compared to patients with atherosclerotic or healthy subjects.
Evidence Level 2
Technical Efficacy Stage 2
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BACKGROUND: Evidence is mounting that first-pass complete recanalization during mechanical thrombectomy is associated with better clinical outcomes in patients presenting with an emergent large vessel occlusion. We hypothesize that aspiration achieving complete clot ingestion results in higher first-pass successful recanalization with quantitative reduction in distal emboli. METHODS: A patient-specific cerebrovascular replica was connected to a flow loop. Occlusion of the middle cerebral artery was achieved with clot analogs. Independent variables were the diameter of the aspiration catheter (0.054-0.088in) and aspiration pattern (static versus cyclical). Outcome measures were the first-pass rates of complete clot ingestion, the extent of recanalization, and the particle-size distribution of distal emboli. RESULTS: All aspiration catheters were successfully navigated to the occlusion. Complete clot ingestion during aspiration thrombectomy resulted in first-pass complete recanalization in every experiment, only achieved in 21% of experiments with partial ingestion (P<0.0001). Aspiration through the large bore 0.088in device resulted in the highest rates of complete clot ingestion (90%). Cyclical aspiration significantly increased the rate of complete clot ingestion (OR21 [1.6, 266]; P=0.04). In all experiments, complete clot ingestion resulted in fewer and smaller distal emboli. CONCLUSIONS: Complete clot ingestion results in fewer distal emboli and the highest rates of first-pass complete recanalization. The rate of complete ingestion during aspiration thrombectomy is a function of both the inner diameter of the aspiration catheter and use of cyclical aspiration. Funding Source: This study was funded in part by a research grant (NSF Award: 1819491) from the National Science Foundation (NSF). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. Conference Proceeding: This paper was presented in part at the 2018 Annual Meeting of the Society of Vascular & Interventional Neurology (SVIN), November 14-17, 2018 in San Diego, CAmore » « less
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