Analysis of blood flow in an out-of-plane CABG model

2006 ◽  
Vol 291 (1) ◽  
pp. H283-H295 ◽  
Author(s):  
Meena Sankaranarayanan ◽  
Dhanjoo N. Ghista ◽  
Chua Leok Poh ◽  
Tan Yong Seng ◽  
Ghassan S. Kassab
Keyword(s):  
Blood Flow ◽  
Flow Field ◽  
Cardiac Cycle ◽  
Artery Bypass ◽  
Bypass Graft ◽  
Three Dimensional ◽  
Substantial Effect ◽  
Shear Stresses ◽  
Out Of Plane ◽  
Inflow Conditions

Coronary artery bypass graft (CABG) is a routine surgical treatment for ischemic and infarcted myocardium. A large number of CABG fail postoperatively because of intimal hyperplasia within months or years. The cause of this failure is thought to be partly related to the flow patterns and shear stresses acting on the endothelial cells. An accurate representation of the flow field and associated wall shear stress (WSS) requires a detailed three-dimensional (3D) model of the CABG. The purpose of this study is to present a detailed analysis of blood flow in a 3D aorto/left CABG, bypassing the occluded left anterior descending coronary (LAD) artery. The analysis takes into account the influence of the out-of-plane geometry of the graft. The finite volume technique was employed to model the 3D blood flow pattern to determine the velocity and WSS distributions. This study presents the flow field distributions of the velocity and WSS at four instances of the cardiac cycle, two in systole and two in diastole. Our results reveal that the CABG geometry has a significant effect on the velocity distribution. The axial velocity profiles at different instances of the cardiac cycle exhibit strong skewing; significant secondary flow and vortex structures are seen in the in-plane velocity patterns. The maximum WSS on the bed of the occluded LAD artery opposite to the graft junction is 14 Pa in middiastole, whereas there is a significantly lower and more uniform distribution of WSS on the bed of the anastomosis. The present results indicate that nonplanarity of the blood vessel along with the inflow conditions has a substantial effect on the fluid mechanics of CABG that contribute to the patency of graft.

Numerical study of hemodynamics after stent implantation during the cardiac cycle

2021 ◽  
Vol 15 (2) ◽  
pp. 8016-8028
Author(s):  
Abdelhakem Belaghit ◽  
B. Aour ◽  
M. Larabi ◽  
A. A. Tadjeddine ◽  
S. Mebarki
Keyword(s):  
Blood Flow ◽  
Stent Implantation ◽  
Cardiac Cycle ◽  
Numerical Study ◽  
Shear Stresses ◽  
Flow Profile ◽  
Hemodynamic State ◽  
Dynamics Simulations ◽  
Medical Planning

The descending aortic aneurysm is one of the most catastrophic cardiovascular emergencies resulting in high mortality worldwide. Clinical observations have pointed out that stent implantation in the sick aorta should probably allow stabilization of the hemodynamic state of the patient's aorta. To better understand the hemodynamic impact of a stent-treated aneurysm, numerical simulations are used to evaluate hemodynamic parameters. These latter including flow profile, velocity distribution, aortic wall pressure and shear stress, which are difficult to measure in vivo. It should be noted that the numerical modeling assists in medical planning by providing patterns of blood circulation, in particular, the distribution of pressures and shear stresses in the wall. In this context, the pulsatile blood flow in the aneurysmal aorta with stent is studied by CFD (Computational Fluid Dynamics) simulations. Realistic boundary conditions time dependent are prescribed at the level of the different arteries of the complete aorta models. The hemodynamic profile of the aneurysmal aorta with stent was analyzed by contour planes of velocity vectors, pressures and shear stresses at different times during the cardiac cycle. The obtained results made it possible to show the effect of the stent on the improvement of the blood flow by solving the problems of hemodynamic disturbances in the aorta.  The methodology used in this work has revealed detailed and necessary information for the cases studied and shows the interest of the numerical tool for diagnosis and surgery.

Blood Flow in an Out-of-Plane Aorto-left Coronary Sequential Bypass Graft

2009 ◽  
pp. 277-295 ◽  
Author(s):  
Meena Sankaranarayanan ◽  
Dhanjoo N. Ghista ◽  
Leok Poh Chua ◽  
Tan Yong Seng ◽  
Kannan Sundaravadivelu ◽  
...  
Keyword(s):  
Blood Flow ◽  
Bypass Graft ◽  
Out Of Plane ◽  
Sequential Bypass

Stress Distributions Along the Inner Wall of the Femoropopliteal Bypass Graft Anastomoses

2004 ◽  
Author(s):  
Triona Campbell ◽  
Reena Cole ◽  
Mark Davies ◽  
Michael O’Donnell
Keyword(s):  
Significant Role ◽  
Atherosclerotic Plaque ◽  
Numerical Models ◽  
Artery Bypass ◽  
Bypass Graft ◽  
Shear Stresses ◽  
Stress Distributions ◽  
Femoropopliteal Bypass ◽  
Artery Bypass Graft ◽  
Femoropopliteal Artery

The distal junction of a femoral or femoropopliteal artery bypass graft has a predilection for failure due to restenosis. However neither the initiation nor proliferation process of atherosclerotic plaque is completely understood. Presently it is hypothesized that the process of atherosclerosis initiates as a result of damage or ‘insult’ to the endothelium. The cause of this initial damage is unknown, although it is widely believed that wall shear stresses are a contributing factor. The primary cause of plaque proliferation has not yet been identified, however it is our belief that intramural pressure plays a significant role. In this study numerical models of the proximal and distal junctions were used to determine both the location and magnitude of the stresses caused by intramural pressure. The simulated artery bypass graft was examined under both static and dynamic conditions.

Flow field and mass transport analysis in arteries with longitudinal ridges

1976 ◽  
Vol 41 (6) ◽  
pp. 910-919 ◽  
Author(s):  
L. H. Back ◽  
D. W. Crawford ◽  
R. Barndt
Keyword(s):  
Flow Field ◽  
Three Dimensional ◽  
Shear Stresses ◽  
Time Varying ◽  
Intimal Thickening ◽  
Three Dimensional Flow ◽  
Longitudinal Vortices ◽  
Arterial Walls ◽  
Transport Analysis

Recent observations have indicated that the earliest lesions of atherosclerosis frequently take the form of longitudinal and helical ridges in arteries of man. Since longitudinal vortices are expected to be present in the troughs between the longitudinal ridges, an analysis was carried out to investigate the three-dimensional flow field and the trasport of lipoproteins and oxygen molecules to arterial walls in the presence of such vortices. The calculations revealed that local hypoxia and lipoprotein accumulation mayoccur at the ridges, leading to subsequent intimal thickening and ridge growth. Higher shear stresses, calculated in the troughs between ridges, may also partially damage the endothelium and lead to intimal thickening and subsequent merging of the ridges. Meaningful measurements are needed in vivo to determine the strength of the vortices, their time-varying behavior, and the actual transverse variations in shear stress, oxygen transport, and lipoprotein accumulation from trough to ridge regions, in order to appraise the present findings and to learn more about the observed progressive thickening and widening of ridges with increasing degrees of intimal thickening and atherosclerosis.

Refined First-Order Shear Deformation Theory Models for Composite Laminates

2003 ◽  
Vol 70 (3) ◽  
pp. 381-390 ◽  
Author(s):  
F. Auricchio ◽  
E. Sacco
Keyword(s):  
Shear Deformation ◽  
Analytical Solutions ◽  
Composite Laminates ◽  
Three Dimensional ◽  
Shear Deformation Theory ◽  
Quadratic Functions ◽  
Shear Stresses ◽  
Stress Profile ◽  
First Order ◽  
Out Of Plane

In the present work, new mixed variational formulations for a first-order shear deformation laminate theory are proposed. The out-of-plane stresses are considered as primary variables of the problem. In particular, the shear stress profile is represented either by independent piecewise quadratic functions in the thickness or by satisfying the three-dimensional equilibrium equations written in terms of midplane strains and curvatures. The developed formulations are characterized by several advantages: They do not require the use of shear correction factors as well as the out-of-plane shear stresses can be derived without post-processing procedures. Some numerical applications are presented in order to verify the effectiveness of the proposed formulations. In particular, analytical solutions obtained using the developed models are compared with the exact three-dimensional solution, with other classical laminate analytical solutions and with finite element results. Finally, we note that the proposed formulations may represent a rational base for the development of effective finite elements for composite laminates.

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