scholarly journals Acute Stent-Induced Endothelial Denudation: Biomechanical Predictors of Vascular Injury

2021 ◽  
Vol 8 ◽  
Author(s):  
Claire Conway ◽  
Farhad R. Nezami ◽  
Campbell Rogers ◽  
Adam Groothuis ◽  
James C. Squire ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Numerical Simulations ◽  
Vascular Injury ◽  
Ex Vivo ◽  
Circumferential Stress ◽  
Arterial Injury ◽  
Stent Design ◽  
Endothelial Denudation ◽  
Wall Shear

Recent concern for local drug delivery and withdrawal of the first Food and Drug Administration-approved bioresorbable scaffold emphasizes the need to optimize the relationships between stent design and drug release with imposed arterial injury and observed pharmacodynamics. In this study, we examine the hypothesis that vascular injury is predictable from stent design and that the expanding force of stent deployment results in increased circumferential stress in the arterial tissue, which may explain acute injury poststent deployment. Using both numerical simulations and ex vivo experiments on three different stent designs (slotted tube, corrugated ring, and delta wing), arterial injury due to device deployment was examined. Furthermore, using numerical simulations, the consequence of changing stent strut radial thickness on arterial wall shear stress and arterial circumferential stress distributions was examined. Regions with predicted arterial circumferential stress exceeding a threshold of 49.5 kPa compared favorably with observed ex vivo endothelial denudation for the three considered stent designs. In addition, increasing strut thickness was predicted to result in more areas of denudation and larger areas exposed to low wall shear stress. We conclude that the acute arterial injury, observed immediately following stent expansion, is caused by high circumferential hoop stresses in the interstrut region, and denuded area profiles are dependent on unit cell geometric features. Such findings when coupled with where drugs move might explain the drug–device interactions.

Effects of Cardiovascular Stent Design on Wall Shear Stress Distribution in Straight and Curved Arteries

2013 ◽  
Vol 284-287 ◽  
pp. 1642-1646
Author(s):  
Hao Ming Hsiao ◽  
Ying Chih Liao ◽  
Chien Han Lin ◽  
Fang Yu Liu ◽  
Yu Ming Tsuei
Keyword(s):  
Shear Stress ◽  
Stress Distribution ◽  
Wall Shear Stress ◽  
Shear Stress Distribution ◽  
Stent Design ◽  
Wall Shear Stress Distribution ◽  
Cardiovascular Stent ◽  
Low Shear Stress ◽  
Wall Shear ◽  
Low Shear

he stent is a major breakthrough in the treatment of coronary artery diseases. The permanent vascular implant of a stent, however, changes the intra-stent blood hemodynamics. There is a growing consensus that the stent implant may change the artery wall shear stress distribution and therefore trigger the restenosis process. Several studies have suggested that low shear stress, particularly the shear stress less than 5 dyne/cm2, may lead to endothelial proliferation of smooth muscle cells. Computational fluid dynamics (CFD) has been widely used to analyze hemodynamics in stented arteries. In this paper, CFD models were developed to investigate the effects of cardiovascular stent design on the wall shear stress distribution in straight and curved arteries. Results show that the stent design pattern alone did not have a significant impact on the stent hemodynamics; however, stenting in curved arteries increased the low shear stress area which may lead to higher restenosis rate. The low shear stress area was almost doubled when the degree of artery curvature increased from 0o to 90o. The proposed methodology and findings will provide great insight for future optimization of stent design to reduce the risk of restenosis.

In Vitro, Time-Resolved PIV Comparison of the Effect of Stent Design on Wall Shear Stress

2009 ◽  
Vol 37 (7) ◽  
pp. 1310-1321 ◽  
Author(s):  
John Charonko ◽  
Satyaprakash Karri ◽  
Jaime Schmieg ◽  
Santosh Prabhu ◽  
Pavlos Vlachos
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Stent Design ◽  
Time Resolved ◽  
Wall Shear

scholarly journals Mesenteric lymph flow in adult and aged rats

2011 ◽  
Vol 301 (5) ◽  
pp. H1828-H1840 ◽  
Author(s):  
Tony J. Akl ◽  
Takashi Nagai ◽  
Gerard L. Coté ◽  
Anatoliy A. Gashev
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Ex Vivo ◽  
Lymphatic Vessels ◽  
Lymph Flow ◽  
Contraction Frequency ◽  
Stress Load ◽  
Wall Shear ◽  
Contractile Characteristics

The objective of study was to evaluate the aging-associated changes, contractile characteristics of mesenteric lymphatic vessels (MLV), and lymph flow in vivo in male 9- and 24-mo-old Fischer-344 rats. Lymphatic diameter, contraction amplitude, contraction frequency, and fractional pump flow, lymph flow velocity, wall shear stress, and minute active wall shear stress load were determined in MLV in vivo before and after Nω-nitro-l-arginine methyl ester hydrochloride (l-NAME) application at 100 μM. The active pumping of the aged rat MLV in vivo was found to be severely depleted, predominantly through the aging-associated decrease in lymphatic contractile frequency. Such changes correlate with enlargement of aged MLV, which experienced much lower minute active shear stress load than adult vessels. At the same time, pumping in aged MLV in vivo may be rapidly increased back to levels of adult vessels predominantly through the increase in contraction frequency induced by nitric oxide (NO) elimination. Findings support the idea that in aged tissues surrounding the aged MLV, the additional source of some yet unlinked lymphatic contraction-stimulatory metabolites is counterbalanced or blocked by NO release. The comparative analysis of the control data obtained from experiments with both adult and aged MLV in vivo and from isolated vessel-based studies clearly demonstrated that ex vivo isolated lymphatic vessels exhibit identical contractile characteristics to lymphatic vessels in vivo.

scholarly journals Optimization of stent designs regarding the thrombosis risk using computational fluid dynamics

2018 ◽  
Vol 4 (1) ◽  
pp. 93-96
Author(s):  
Carolin Wüstenhagen ◽  
Sylvia Pfensig ◽  
Stefan Siewert ◽  
Sebastian Kaule ◽  
Niels Grabow ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Stent Thrombosis ◽  
Fluid Simulation ◽  
Design Parameters ◽  
Stent Design ◽  
Thrombosis Risk ◽  
Wall Shear

AbstractIn-stent thrombosis is a major complication of stent implantations. Unlike pathological occurrences as in-stent restenosis for instance, thrombosis represents an acute event associated with high mortality rates. Experiments show that low wall shear stress promotes undirected endothelial cell coverage of the vessel wall and therefore increases the risk of thrombus formation. Stent design represents a crucial factor influencing the surface areas of low wall shear stress and thus the incidence of acute in-stent thrombosis. In this study, we present an optimization method for stent designs with minimized thrombosis risk. A generic stent design was developed, based on five different stent design parameters. Optimization was conducted based on computational fluid dynamics analysis and the gradient-free Nelder-Mead approach. For each optimization step, a numerical fluid simulation was performed in a vessel with a reference vessel diameter of 2.70 mm with stent-overexpansion ratio of 1.0:1.1. For each numerical fluid simulation a physiological Reynolds number of 250, resulting in a mean velocity of 0.331 m/s at the inlet and a laminar flow as well as stiff vessel walls were assumed. The impact of different stent designs was analyzed based on the wall shear stress distribution. As a basis for the comparison of different stent designs, a dimensionless thrombosis risk number was calculated from the area of low wall shear stress and the overall stented area. The first two optimization steps already provide a decrease of thrombosis risk of approximately 83%. In conclusion, computational fluid dynamic analyses and optimization methods usind the Nelder-Mead approach represent a useful tool for the development of hemodynamically optimized stent designs with minimized thrombosis risk.

Steady Flow in an Aneurysm Model: Correlation Between Fluid Dynamics and Blood Platelet Deposition

1996 ◽  
Vol 118 (3) ◽  
pp. 280-286 ◽  
Author(s):  
D. Bluestein ◽  
L. Niu ◽  
R. T. Schoephoerster ◽  
M. K. Dewanjee
Keyword(s):  
Fluid Dynamics ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Numerical Simulations ◽  
Recirculation Zone ◽  
Blood Platelet ◽  
Platelet Deposition ◽  
Order Of Magnitude ◽  
Wall Shear ◽  
Aneurysm Model

Laminar and turbulent numerical simulations of steady flow in an aneurysm model were carried out over Reynolds numbers ranging from 300 to 3600. The numerical simulations are validated with Digital Particle Image Velocimetry (DPIV) measurements, and used to study the fluid dynamic mechanisms that characterize aneurysm deterioration, by correlating them to in vitro blood platelet deposition results. It is shown that the recirculation zone formed inside the aneurysm cavity creates conditions that promote thrombus formation and the viability of rupture. Wall shear stress values in the recirculation zone are around one order of magnitude less than in the entrance zone. The point of reattachment at the distal end of the aneurysm is characterized by a pronounced wall shear stress peak. As the Reynolds number increases in laminar flow, the center of the recirculation region migrates toward the distal end of the aneurysm, increasing the pressure at the reattachment point. Under fully turbulent flow conditions (Re = 3600) the recirculation zone inside the aneurysm shrinks considerably. The wall shear stress values are almost one order of magnitude larger than those for the laminar cases. The fluid dynamics mechanisms inferred from the numerical simulation were correlated with measurements of blood platelet deposition, offering useful explanations for the different morphologies of the platelet deposition curves.

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