scholarly journals Vascular Resistance in the Carotid Artery: An In Vitro Investigation of Embolic Protection Filters

2008 ◽  
Vol 19 (10) ◽  
pp. 1467-1476 ◽  
Author(s):  
Gail M. Siewiorek ◽  
Mark H. Wholey ◽  
Ender A. Finol
Keyword(s):  
Carotid Artery ◽  
Vascular Resistance ◽  
Embolic Protection ◽  
In Vitro Investigation

In Vitro Performance Assessment of Distal Protection Devices for Carotid Artery Stenting: Effect of Physiological Anatomy on Vascular Resistance

2007 ◽  
Vol 14 (5) ◽  
pp. 712-724 ◽  
Author(s):  
Gail M. Siewiorek ◽  
Mark H. Wholey ◽  
Ender A. Finol
Keyword(s):  
Carotid Artery ◽  
Pressure Gradient ◽  
Vascular Resistance ◽  
Flow Rate ◽  
Volume Flow Rate ◽  
Volume Flow ◽  
Physiological Anatomy ◽  
Protection Devices ◽  
Distal Protection

Purpose: To assess in vitro the performance of 5 distal protection devices (DPDs) by evaluating the capture efficiency, pressure gradient, volume flow rate, and vascular resistance in the internal carotid artery (ICA). Methods: The time-averaged mean peak velocity in the common carotid artery and a blood-mimicking solution were used to simulate physiological conditions in a silicone carotid phantom representing average human carotid artery geometry with a 70% symmetrical ICA stenosis. Five milligrams of dyed 200-μm nominal diameter polymer microspheres (larger than the pore size of the devices, except Spider RX, which was tested with 300-μm-diameter particles) were injected into the ICA. The percentages of particles missed after injection and lost during device retrieval were measured for the 5 devices (Spider RX, FilterWire EZ, RX Accunet, Angioguard XP, and Emboshield). The normalized pressure gradient, fraction of the volume flow rate, and vascular resistance in the ICA were calculated. Results: Spider RX captured the most particles (missing 0.06%, p<0.05) and yielded the smallest normalized pressure gradient increase (4.2%), the largest volume flow rate fraction (0.40), and the smallest vascular resistance in the ICA (272 mmHg/L·min−1, a 5.4% increase with respect to initial conditions). Angioguard XP captured the fewest particles (missing 36.3%, p<0.05 except Emboshield) and resulted in the largest normalized pressure gradient increase (37%) in the ICA. RX Accunet produced the smallest volume flow rate fraction in the ICA (0.30) and the largest vascular resistance in the ICA (470 mmHg/L·min−1, an 82.2% increase). Emboshield migrated ∼6 cm distal to the original position after particle injection. FilterWire EZ lost the fewest particles during retrieval (0.45%, p<0.05 except Accunet RX and Spider RX) and had the best overall performance with 200-μm emboli (p<0.05 except Accunet RX). Conclusion: None of the devices tested completely prevented embolization. Overall, Spider RX had the best performance and is conjectured to have the best wall apposition of the devices tested. Vascular resistance should be considered a key filter design parameter for performance testing since it represents a quantitative estimation of the “slow-flow phenomenon.” Our findings should be extrapolated cautiously to help interventionists choose the best device.

Permeability and Porosity of Embolic Protection Filters: An Experimental Study

2008 ◽  
Author(s):  
Gail M. Siewiorek ◽  
Ender A. Finol
Keyword(s):  
Carotid Artery ◽  
Flow Rate ◽  
Optimization Approach ◽  
Embolic Protection ◽  
High Resolution Images ◽  
Computational Fluid Dynamics Simulations ◽  
Protection Devices ◽  
Distal Perfusion ◽  
Dynamics Simulations

Endovascular therapies are an evolving form of treatment for stenosed atherosclerotic blood vessels. In particular, stenting and angioplasty of the carotid artery has recently gained more attention. Due to risk of periprocedural distal embolization, cerebral protection devices such as embolic protection filters (EPFs), which maintain distal perfusion during the intervention, have been developed to capture embolized plaque particles. This investigation studied in vitro the effects of a deployed EPF on flow rate in the internal carotid artery. The pseudopermeability of each device was calculated by maintaining a constant pressure gradient during its deployed state and after injection of emboli by adjusting the flow rate. High resolution images were used to calculate the porosity of each device. Experimentally-determined permeability and porosity can be used in computational fluid dynamics simulations as a design optimization approach to determine the optimal pore size for each EPF.

scholarly journals Use of Micropatterned Thin Film Nitinol in Carotid Stents to Augment Embolic Protection

2016 ◽  
Author(s):  
Mahdis Shayan ◽  
Brian T. Jankowitz ◽  
Puneeth Shridhar ◽  
Youngjae Chun
Keyword(s):  
Thin Film ◽  
Carotid Artery ◽  
Covered Stent ◽  
In Vitro Tests ◽  
Embolic Protection ◽  
Low Profile ◽  
Study Results ◽  
In Vivo Testing

Stenting is an alternative to endarterectomy for the treatment of carotid artery stenosis. However, stenting is associated with a higher risk of procedural stroke secondary to distal thromboembolism. Hybrid stents with a micromesh layer have been proposed to address this complication. We developed a micropatterned thin film nitinol (M-TFN) covered stent designed to prevent thromboembolism during carotid intervention. This innovation may obviate the need or work synergistically with embolic protection devices. The proposed double layered stent is low-profile, thromboresistant, and covered with a M-TFN that can be fabricated with fenestrations of varying geometries and sizes. The M-TFN was created in multiple geometries, dimensions, and porosities by sputter deposition. The efficiency of various M-TFN to capture embolic particles was evaluated in different atherosclerotic carotid stenotic conditions through in vitro tests. The covered stent prevented emboli dislodgement in the range of 70-96% during 30min duration tests. In vitro vascular cell growth study results showed that endothelial cell elongation, alignment and growth behaviour silhouettes significantly enhance specifically on the diamond-shape M-TFN with the dimensions of 145&micro;m&times;20&micro;m and a porosity of 32%. Future studies will require in-vivo testing. Our results demonstrate that M-TFN has a promising potential for carotid artery stenting.

The Effect of Embolic Protection Filters on Distal Embolization and Slow Flow Condition in Carotid Artery Stenting

2007 ◽  
Author(s):  
Gail M. Siewiorek ◽  
Ender A. Finol
Keyword(s):  
Carotid Artery ◽  
Flow Rate ◽  
Carotid Artery Stenting ◽  
Carotid Artery Disease ◽  
The United States ◽  
Distal Embolization ◽  
Embolic Protection ◽  
Distal Perfusion ◽  
Protection Filter

Strokes are the third leading cause of death in the United States today. Carotid artery stenting (CAS) used in conjunction with a cerebral protection device (CPD) is a current alternative treatment for severe carotid artery disease. A type of CPD, an embolic protection filter (EPF), has received attention recently due to its allowance of distal perfusion during use. This investigation studied the effects of four EPFs (Spider RX, FilterWire EZ, RX Accunet, Emboshield) on both pressure gradient and flow rate in the internal carotid artery (ICA) in vitro. Dyed polymer microspheres larger than the pore size of the devices tested were injected into the ICA of a 70% stenosed carotid artery model. The percentage of particles missed was calculated. None of the devices tested were able to completely prevent embolization. Emboshield had the least desirable performance (missing 35.4% of particles) while Spider RX had the best (missing 0.06%). A decrease in flow rate and an increase in pressure drop were seen after the device was filled with particles. From these results, it is inferred that improper wall apposition is the primary cause for inadequate capture efficiency rates, which may lead to an increase in distal embolization and stroke.

In vitro investigation of Varizella zoster virus as an oncolytic virus in glioblastoma therapy

2008 ◽  
Vol 35 (S 01) ◽  
Author(s):  
H Leske ◽  
A Baiker ◽  
C Schichor ◽  
J.C Tonn ◽  
R Goldbrunner ◽  
...  
Keyword(s):  
Oncolytic Virus ◽  
In Vitro Investigation ◽  
Varizella Zoster Virus

LY53857, a 5HT2 Receptor Antagonist, Delays Occlusion and Inhibits Platelet Aggregation in a Rabbit Model of Carotid Artery Occlusion

1991 ◽  
Vol 66 (03) ◽  
pp. 355-360 ◽  
Author(s):  
Harve C Wilson ◽  
William Coffman ◽  
Anne L Killam ◽  
Marlene L Cohen
Keyword(s):  
Electrical Stimulation ◽  
Platelet Aggregation ◽  
Carotid Artery ◽  
Receptor Antagonist ◽  
Artery Occlusion ◽  
Carotid Artery Occlusion ◽  
Rabbit Platelet ◽  
Rabbit Platelets ◽  
5Ht2 Receptor

SummaryThe present study was designed to evaluate the effectiveness of the ergoline 5HT2 receptor antagonist, LY53857 in a rabbit model of vascular arterial occlusion. LY53857 (1 and 10 εM) inhibited serotonin amplified platelet aggregation responses to threshold concentrations of ADP in rabbit platelets in vitro. LY53857 (1 εM) not only inhibited the serotonin component of rabbit platelet aggregation, but also inhibited in vitro aggregation induced by ADP (48.7 ± 16.7% inhibition), collagen (76.1 ± 15.9% inhibition) and U46619 (65.2 ± 12.3% inhibition). The effectiveness of this ergoline 5HT2 receptor antagonist in blocking aggregation to ADP, collagen and U46619 may be related to its ability to inhibit a serotonin component of platelet aggregation since rabbit platelets possess high concentrations of serotonin that may be released during aggregation produced by other agents. Based on the effectiveness of LY53857 to inhibit rabbit platelet aggregation, we explored the ability of LY53857 to extend the time to carotid artery occlusion in rabbits following electrical stimulation of the artery. Reproducible carotid artery occlusion was induced in rabbits by moderate stenosis coupled to arterial cross clamping, followed by electrical stimulation. With this procedure, occlusion occurred at 47.0 ± 7 min (n = 30) after initiation of the electrical stimulation. Animals pretreated with LY53857 (50 to 500 εg/kg i.v.) showed a delay in the time to carotid artery occlusion (at 100 εg/kg i.v. occlusion time extended to 164 ± 16 min). Furthermore, ex vivo platelet aggregation from animals treated with LY53857 (300 εg/kg i.v.) resulted in 40.5% inhibition of platelet aggregation in response to the combination of ADP (1 εM) and serotonin (1 εM). These studies document the ability to obtain reproducible arterial occlusion in the rabbit and showed that intravenously administered LY53857 prolonged the time to carotid artery occlusion. Prolongation of carotid artery occlusion time was accompanied by inhibition of serotonin-amplified ADP-induced aggregation in rabbit platelets, an effect observed both in vitro and ex vivo. Thus, the rabbit is a useful model for studying the effectiveness of 5HT2 receptor antagonists in prolonging vascular occlusion induced by insult of the carotid artery.

Methylprednisolone on circulating eicosanoids and vasomotor tone after endotoxin

1986 ◽  
Vol 61 (1) ◽  
pp. 185-191 ◽  
Author(s):  
C. A. Hales ◽  
R. D. Brandstetter ◽  
C. F. Neely ◽  
M. B. Peterson ◽  
D. Kong ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Vascular Resistance ◽  
Systemic Blood Pressure ◽  
Physiological Effect ◽  
High Dose ◽  
Systemic Blood ◽  
Eicosanoid Production ◽  
Circulating Levels

Acute pulmonary and systemic vasomotor changes induced by endotoxin in dogs have been related, at least in part, to the production of eicosanoids such as the vasoconstrictor thromboxane and the vasodilator prostacyclin. Steroids in high doses, in vitro, inhibit activation of phospholipase A2 and prevent fatty acid release from cell membranes to enter the arachidonic acid cascade. We, therefore, administered methylprednisolone (40 mg/kg) to dogs to see if eicosanoid production and the ensuing vasomotor changes could be prevented after administration of 150 micrograms/kg of endotoxin. The stable metabolites of thromboxane B2 (TxB2) and 6-ketoprostaglandin F1 alpha (6-keto-PGF1 alpha) were measured by radioimmunoassay. Methylprednisolone by itself did not alter circulating eicosanoids but when given 2.5 h before endotoxin not only failed to inhibit endotoxin-induced eicosanoid production but actually resulted in higher circulating levels of 6-keto-PGF1 alpha (P less than 0.05) compared with animals receiving endotoxin alone. Indomethacin prevented the steroid-enhanced concentrations of 6-keto-PGF1 alpha after endotoxin and prevented the greater fall (P less than 0.05) in systemic blood pressure and systemic vascular resistance with steroid plus endotoxin than occurred with endotoxin alone. Administration of methylprednisolone immediately before endotoxin resulted in enhanced levels (P less than 0.05) of both TxB2 and 6-keto-PGF1 alpha but with a fall in systemic blood pressure and vascular resistance similar to the animals pretreated by 2.5 h. In contrast to the early steroid group in which all of the hypotensive effect was due to eicosanoids, in the latter group steroids had an additional nonspecific effect. Thus, in vivo, high-dose steroids did not prevent endotoxin-induced increases in eicosanoids but actually increased circulating levels of TxB2 and 6-keto-PGF1 alpha with a physiological effect favoring vasodilation.

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