Endothelial inflammation and monocyte adhesion following increased vascular wall shear stress in an ex vivo femoral artey model (670.10)

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.

Download Full-text

High Wall Shear Stress can Predict Wall Degradation in Ascending Aortic Aneurysms: An Integrated Biomechanics Study

Frontiers in Bioengineering and Biotechnology ◽

10.3389/fbioe.2021.750656 ◽

2021 ◽

Vol 9 ◽

Author(s):

M. Yousuf Salmasi ◽

Selene Pirola ◽

Sumesh Sasidharan ◽

Serena M. Fisichella ◽

Alberto Redaelli ◽

...

Keyword(s):

Shear Stress ◽

Wall Shear Stress ◽

Computational Modelling ◽

Vascular Wall ◽

Aortic Aneurysms ◽

Patient Specific ◽

Segmental Analysis ◽

4D Mri ◽

Wall Shear ◽

Mechanical And Microstructural Properties

Background: Blood flow patterns can alter material properties of ascending thoracic aortic aneurysms (ATAA) via vascular wall remodeling. This study examines the relationship between wall shear stress (WSS) obtained from image-based computational modelling with tissue-derived mechanical and microstructural properties of the ATAA wall using segmental analysis.Methods: Ten patients undergoing surgery for ATAA were recruited. Exclusions: bicuspid aortopathy, connective tissue disease. All patients had pre-operative 4-dimensional flow magnetic resonance imaging (4D-MRI), allowing for patient-specific computational fluid dynamics (CFD) analysis and anatomically precise WSS mapping of ATAA regions (6–12 segments per patient). ATAA samples were obtained from surgery and subjected to region-specific tensile and peel testing (matched to WSS segments). Computational pathology was used to characterize elastin/collagen abundance and smooth muscle cell (SMC) count.Results: Elevated values of WSS were predictive of: reduced wall thickness [coef −0.0489, 95% CI (−0.0905, −0.00727), p = 0.022] and dissection energy function (longitudinal) [−15,0, 95% CI (−33.00, −2.98), p = 0.048]. High WSS values also predicted higher ultimate tensile strength [coef 0.136, 95% CI (0 0.001, 0.270), p = 0.048]. Additionally, elevated WSS also predicted a reduction in elastin levels [coef −0.276, 95% (CI −0.531, −0.020), p = 0.035] and lower SMC count ([oef −6.19, 95% CI (−11.41, −0.98), p = 0.021]. WSS was found to have no effect on collagen abundance or circumferential mechanical properties.Conclusions: Our study suggests an association between elevated WSS values and aortic wall degradation in ATAA disease. Further studies might help identify threshold values to predict acute aortic events.

Download Full-text

Wall shear stress measurement method based on parallel flow model near vascular wall in echography

Japanese Journal of Applied Physics ◽

10.7567/jjap.56.07jf08 ◽

2017 ◽

Vol 56 (7S1) ◽

pp. 07JF08 ◽

Cited By ~ 4

Author(s):

Motochika Shimizu ◽

Tomohiko Tanaka ◽

Takashi Okada ◽

Yoshinori Seki ◽

Tomohide Nishiyama

Keyword(s):

Shear Stress ◽

Wall Shear Stress ◽

Measurement Method ◽

Flow Model ◽

Stress Measurement ◽

Vascular Wall ◽

Parallel Flow ◽

Wall Shear ◽

Wall Shear Stress Measurement

Download Full-text

Mesenteric lymph flow in adult and aged rats

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00538.2011 ◽

2011 ◽

Vol 301 (5) ◽

pp. H1828-H1840 ◽

Cited By ~ 46

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.

Download Full-text

Association of Early Atherosclerosis with Vascular Wall Shear Stress in Hypercholesterolemic Zebrafish

PLoS ONE ◽

10.1371/journal.pone.0142945 ◽

2015 ◽

Vol 10 (11) ◽

pp. e0142945 ◽

Cited By ~ 4

Author(s):

Sang Joon Lee ◽

Woorak Choi ◽

Eunseok Seo ◽

Eunseop Yeom

Keyword(s):

Shear Stress ◽

Wall Shear Stress ◽

Vascular Wall ◽

Wall Shear ◽

Early Atherosclerosis

Download Full-text

Correlations Among Indicators of Disturbed Flow at the Normal Carotid Bifurcation

Journal of Biomechanical Engineering ◽

10.1115/1.3127252 ◽

2009 ◽

Vol 131 (6) ◽

Cited By ~ 147

Author(s):

Sang-Wook Lee ◽

Luca Antiga ◽

David A. Steinman

Keyword(s):

Shear Stress ◽

Wall Shear Stress ◽

Carotid Bifurcation ◽

Vascular Wall ◽

Spatial Gradient ◽

Disturbed Flow ◽

Relative Residence Time ◽

Gradient Based ◽

Wall Shear ◽

Dynamics Simulations

A variety of hemodynamic wall parameters (HWP) has been proposed over the years to quantify hemodynamic disturbances as potential predictors or indicators of vascular wall dysfunction. The aim of this study was to determine whether some of these might, for practical purposes, be considered redundant. Image-based computational fluid dynamics simulations were carried out for N=50 normal carotid bifurcations reconstructed from magnetic resonance imaging. Pairwise Spearman correlation analysis was performed for HWP quantifying wall shear stress magnitudes, spatial and temporal gradients, and harmonic contents. These were based on the spatial distributions of each HWP and, separately, the amount of the surface exposed to each HWP beyond an objectively-defined threshold. Strong and significant correlations were found among the related trio of time-averaged wall shear stress magnitude (TAWSS), oscillatory shear index (OSI), and relative residence time (RRT). Wall shear stress spatial gradient (WSSG) was strongly and positively correlated with TAWSS. Correlations with Himburg and Friedman’s dominant harmonic (DH) parameter were found to depend on how the wall shear stress magnitude was defined in the presence of flow reversals. Many of the proposed HWP were found to provide essentially the same information about disturbed flow at the normal carotid bifurcation. RRT is recommended as a robust single metric of low and oscillating shear. On the other hand, gradient-based HWP may be of limited utility in light of possible redundancies with other HWP, and practical challenges in their measurement. Further investigations are encouraged before these findings should be extrapolated to other vascular territories.

Download Full-text