scholarly journals Computational Analysis of Wall Shear Stress Patterns on Calcified and Bicuspid Aortic Valves: Focus on Radial and Coaptation Patterns

Fluids ◽  
2021 ◽  
Vol 6 (8) ◽  
pp. 287
Author(s):  
Huseyin Enes Salman ◽  
Levent Saltik ◽  
Huseyin C. Yalcin
Keyword(s):  
Aortic Valve ◽  
Three Dimensional ◽  
Shear Stresses ◽  
Aortic Valves ◽  
Bicuspid Valve ◽  
Valve Function ◽  
Valvular Diseases ◽  
Wall Shear ◽  
Stress Patterns ◽  
Valve Formation

Calcification and bicuspid valve formation are important aortic valve disorders that disturb the hemodynamics and the valve function. The detailed analysis of aortic valve hemodynamics would lead to a better understanding of the disease’s etiology. We computationally modeled the aortic valve using simplified three-dimensional geometry and inlet velocity conditions obtained via echocardiography. We examined various calcification severities and bicuspid valve formation. Fluid-structure interaction (FSI) analyses were adapted using ANSYS Workbench to incorporate both flow dynamics and leaflet deformation accurately. Simulation results were validated by comparing leaflet movements in B-mode echo recordings. Results indicate that the biomechanical environment is significantly changed for calcified and bicuspid valves. High flow jet velocities are observed in the calcified valves which results in high transvalvular pressure difference (TPG). Wall shear stresses (WSS) increased with the calcification on both fibrosa (aorta side) and ventricularis (left ventricle side) surfaces of the leaflet. The WSS distribution is regular on the ventricularis, as the WSS values proportionally increase from the base to the tip of the leaflet. However, WSS patterns are spatially complex on the fibrosa side. Low WSS levels and spatially complex WSS patterns on the fibrosa side are considered as promoting factors for further calcification and valvular diseases.

Three-Dimensional Numerical Simulation of the Fluid Dynamics in a Coronary Stent

2009 ◽  
Author(s):  
F. Gori ◽  
A. Boghi ◽  
M. Amitrano
Keyword(s):  
Fluid Dynamic ◽  
Three Dimensional ◽  
Coronary Stent ◽  
Shear Stresses ◽  
Unsteady State ◽  
Hemodynamic Variables ◽  
Stent Geometry ◽  
Severe Coronary Artery ◽  
Wall Shear ◽  
Artery Disease

Stents are commonly used to restore blood flow in patients with severe coronary artery disease. Local hemodynamic variables, as wall shear stress, have an important role in the restenosis and their distribution depends on the stent geometry. The objective of the present study is to carry out CFD simulations in a realistic 3D geometry of a coronary stent in physiological conditions. A comparison is performed between two reconstructed stents, made of 12 rings and similar to the real coronary ones, which differ by the position of the struts, where the first type is with closed cells and the second one with open cells. The artery is modeled as a cylinder with rigid walls and the blood is assumed as incompressible Newtonian fluid in laminar flow with constant physical properties. The commercial computational fluid dynamic code FLUENT is used with a mesh composed of non uniform tetrahedrons. The simulations are performed in steady and unsteady state. Wall shear stresses, WSS, as well as its time variations, are investigated in unsteady state with the conclusion that the stent with closed cells have a better fluid dynamic behavior.

scholarly journals A novel source of arterial valve cells linked to bicuspid aortic valve without raphe in mice

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Lorriane Eley ◽  
Ahlam MS Alqahtani ◽  
Donal MacGrogan ◽  
Rachel V Richardson ◽  
Lindsay Murphy ◽  
...  
Keyword(s):  
Aortic Valve ◽  
Bicuspid Aortic Valve ◽  
Congenital Malformations ◽  
Heart Valves ◽  
Atrioventricular Valve ◽  
Aortic Valves ◽  
Mesenchymal Transition ◽  
Valve Interstitial Cells ◽  
Valve Formation ◽  
Dependent Mechanism

Abnormalities of the arterial valve leaflets, predominantly bicuspid aortic valve, are the commonest congenital malformations. Although many studies have investigated the development of the arterial valves, it has been assumed that, as with the atrioventricular valves, endocardial to mesenchymal transition (EndMT) is the predominant mechanism. We show that arterial is distinctly different from atrioventricular valve formation. Whilst the four septal valve leaflets are dominated by NCC and EndMT-derived cells, the intercalated leaflets differentiate directly from Tnnt2-Cre+/Isl1+ progenitors in the outflow wall, via a Notch-Jag dependent mechanism. Further, when this novel group of progenitors are disrupted, development of the intercalated leaflets is disrupted, resulting in leaflet dysplasia and bicuspid valves without raphe, most commonly affecting the aortic valve. This study thus overturns the dogma that heart valves are formed principally by EndMT, identifies a new source of valve interstitial cells, and provides a novel mechanism for causation of bicuspid aortic valves without raphe.

Unsteady and Three-Dimensional Simulation of Blood Flow in the Human Aortic Arch

2002 ◽  
Vol 124 (4) ◽  
pp. 378-387 ◽  
Author(s):  
N. Shahcheraghi ◽  
H. A. Dwyer ◽  
A. Y. Cheer ◽  
A. I. Barakat ◽  
T. Rutaganira
Keyword(s):  
Blood Flow ◽  
Aortic Arch ◽  
Thoracic Aorta ◽  
Aortic Wall ◽  
Three Dimensional ◽  
Outer Wall ◽  
Human Aorta ◽  
Shear Stresses ◽  
Descending Thoracic Aorta ◽  
Wall Shear

A three-dimensional and pulsatile blood flow in a human aortic arch and its three major branches has been studied numerically for a peak Reynolds number of 2500 and a frequency (or Womersley) parameter of 10. The simulation geometry was derived from the three-dimensional reconstruction of a series of two-dimensional slices obtained in vivo using CAT scan imaging on a human aorta. The numerical simulations were obtained using a projection method, and a finite-volume formulation of the Navier-Stokes equations was used on a system of overset grids. Our results demonstrate that the primary flow velocity is skewed towards the inner aortic wall in the ascending aorta, but this skewness shifts to the outer wall in the descending thoracic aorta. Within the arch branches, the flow velocities were skewed to the distal walls with flow reversal along the proximal walls. Extensive secondary flow motion was observed in the aorta, and the structure of these secondary flows was influenced considerably by the presence of the branches. Within the aorta, wall shear stresses were highly dynamic, but were generally high along the outer wall in the vicinity of the branches and low along the inner wall, particularly in the descending thoracic aorta. Within the branches, the shear stresses were considerably higher along the distal walls than along the proximal walls. Wall pressure was low along the inner aortic wall and high around the branches and along the outer wall in the ascending thoracic aorta. Comparison of our numerical results with the localization of early atherosclerotic lesions broadly suggests preferential development of these lesions in regions of extrema (either maxima or minima) in wall shear stress and pressure.

scholarly journals Efficient investigation on fully developed flow in a mildly curved 180° open-channel

2014 ◽  
Vol 16 (6) ◽  
pp. 1250-1264 ◽  
Author(s):  
Yuchuan Bai ◽  
Xiaolong Song ◽  
Shuxian Gao
Keyword(s):  
Secondary Flow ◽  
Flow Pattern ◽  
Turbulent Flows ◽  
Three Dimensional ◽  
Engineering Application ◽  
Experimental Investigations ◽  
Shear Stresses ◽  
Fully Developed Flow ◽  
Wall Shear ◽  
Volume Method

Turbulent flow in meandering open channels is one of the most complicated and unpredictable turbulent flows as the interaction of various forces, such as pressure gradient, centrifugal force, and wall shear stresses severely affect the flow pattern. In order to improve significance in engineering application, understanding the overall flow characteristic is the focus. This paper presents the results of numerical and experimental investigations of flow in a 180° mild bend, which is close to criticality with curvature ratio R/B = 3. Considering the characteristic of various models, three-dimensional (3D) re-normalization group (RNG) k–ε model was adopted to simulate the flow efficiently. Governing equations of the flow were solved with a finite-volume method. The pressure-based coupled algorithm was used to compute the pressure. The flow velocities were measured experimentally with Micro acoustic Doppler velocimeter. Good agreement between the numerical results and measurements indicated that RNG k–ε model can successfully predict this flow phenomenon. The flow pattern in this bend is influenced widely by the secondary flow. The variations of velocity components, streamlines, secondary flow, and wall shear stresses are analysed in the study. Some newly discovered phenomenon in this special state are worth noting.

scholarly journals Perioperative evaluation of regional aortic wall shear stress patterns in patients undergoing aortic valve and/or proximal thoracic aortic replacement

2018 ◽  
Vol 155 (6) ◽  
pp. 2277-2286.e2 ◽  
Author(s):  
Emilie Bollache ◽  
Paul W.M. Fedak ◽  
Pim van Ooij ◽  
Ozair Rahman ◽  
S. Chris Malaisrie ◽  
...  
Keyword(s):  
Shear Stress ◽  
Aortic Valve ◽  
Wall Shear Stress ◽  
Aortic Wall ◽  
Aortic Replacement ◽  
Wall Shear ◽  
Stress Patterns

scholarly journals Tricuspidisation of the aortic valve with creation of a crown-like annulus is able to restore a normal valve function in bicuspid aortic valves☆

2006 ◽  
Vol 29 (6) ◽  
pp. 1001-1006 ◽  
Author(s):  
René Prêtre ◽  
Alexander Kadner ◽  
Hitendu Dave ◽  
Dominique Bettex ◽  
Michele Genoni
Keyword(s):  
Aortic Valve ◽  
Aortic Valves ◽  
Bicuspid Aortic Valves ◽  
Valve Function

scholarly journals Transcriptional and phenotypic changes in aorta and aortic valve with aging and MnSOD deficiency in mice

2013 ◽  
Vol 305 (10) ◽  
pp. H1428-H1439 ◽  
Author(s):  
Carolyn M. Roos ◽  
Michael Hagler ◽  
Bin Zhang ◽  
Elise A. Oehler ◽  
Arman Arghami ◽  
...  
Keyword(s):  
Gene Expression ◽  
Aortic Valve ◽  
Endothelial Function ◽  
Related Gene ◽  
Wild Type ◽  
Transcriptional Responses ◽  
Aortic Valves ◽  
Mitochondrial Oxidative Stress ◽  
Age Related ◽  
Valve Function

The purpose of this study was to characterize changes in antioxidant and age-related gene expression in aorta and aortic valve with aging, and test the hypothesis that increased mitochondrial oxidative stress accelerates age-related endothelial and aortic valve dysfunction. Wild-type (MnSOD+/+) and manganese SOD heterozygous haploinsufficient (MnSOD+/−) mice were studied at 3 and 18 mo of age. In aorta from wild-type mice, antioxidant expression was preserved, although there were age-associated increases in Nox2 expression. Haploinsufficiency of MnSOD did not alter antioxidant expression in aorta, but increased expression of Nox2. When compared with that of aorta, age-associated reductions in antioxidant expression were larger in aortic valves from wild-type and MnSOD haploinsufficient mice, although Nox2 expression was unchanged. Similarly, sirtuin expression was relatively well-preserved in aorta from both genotypes, whereas expression of SIRT1, SIRT2, SIRT3, SIRT4, and SIRT6 were significantly reduced in the aortic valve. Expression of p16ink4a, a marker of cellular senescence, was profoundly increased in both aorta and aortic valve from MnSOD+/+ and MnSOD+/− mice. Functionally, we observed comparable age-associated reductions in endothelial function in aorta from both MnSOD+/+ and MnSOD+/− mice. Interestingly, inhibition of NAD(P)H oxidase with apocynin or gp91ds-tat improved endothelial function in MnSOD+/+ mice but significantly impaired endothelial function in MnSOD+/− mice at both ages. Aortic valve function was not impaired by aging or MnSOD haploinsufficiency. Changes in antioxidant and sirtuin gene expression with aging differ dramatically between aorta and aortic valve. Furthermore, although MnSOD does not result in overt cardiovascular dysfunction with aging, compensatory transcriptional responses to MnSOD deficiency appear to be tissue specific.

scholarly journals Diffuse Supravalvular Aortic Stenosis: Surgical Repair in Adulthood

2009 ◽  
Vol 2009 ◽  
pp. 1-3 ◽  
Author(s):  
Giovanni Ferlan ◽  
Claudio De Pasquale ◽  
Concetta Losito ◽  
Annalisa Fiorella ◽  
Nicola Marraudino ◽  
...  
Keyword(s):  
Aortic Valve ◽  
Aortic Stenosis ◽  
Three Dimensional ◽  
Ascending Aorta ◽  
Supravalvular Aortic Stenosis ◽  
Mechanical Prosthesis ◽  
Computed Tomographic ◽  
Valve Function ◽  
Normal Shape

We present the case of a 54-year-old woman in which a diffuse congenital supravalvular aortic stenosis (SVAS) was associated with a severe aortic valve incompetence and heavy calcification of the aortic annulus. Repair consisted in resection of the ascending aorta, patch augmentation of the hypoplastic aortic root and annulus, placement of a 20 mm Dacron tubular graft (Vascutek, Renfrewshire, UK) and aortic valve replacement with a mechanical prosthesis (Sorin, Turin, Italy). Follow-up echocardiography demonstrated normal prosthetic valve function and a postoperative three-dimensional computed tomographic scan showed a normal shape of the reconstructed ascending aorta.

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