Analysis of blood flow in an out-of-plane CABG model
Meena Sankaranarayanan1, Dhanjoo N Ghista, Chua Leok Poh
1School of Mechanical and Aerospace Engineering, National Heart Centre, Singapore.
Insights
Coronary artery bypass graft (CABG) failure is linked to intimal hyperplasia. This study analyzes blood flow and wall shear stress in 3D CABG models, revealing geometry
Area of Science:
- Biomedical Engineering
- Cardiovascular Surgery
- Computational Fluid Dynamics
Background:
- Coronary artery bypass graft (CABG) surgery is common for myocardial ischemia.
- Graft failure, often due to intimal hyperplasia, is a significant clinical issue.
- Blood flow patterns and wall shear stress (WSS) are implicated in graft failure.
Purpose of the Study:
- To conduct a detailed 3D computational fluid dynamics analysis of blood flow in a CABG.
- To investigate the influence of graft geometry, including out-of-plane features, on flow dynamics.
- To determine velocity and WSS distributions within the graft and bypassed artery.
Main Methods:
- Utilized the finite volume technique to model 3D blood flow in an aorto/left CABG.
- Analyzed flow fields and WSS at four distinct cardiac cycle instances (systole and diastole).
- Incorporated the nonplanar geometry of the blood vessel into the computational model.
Main Results:
- CABG geometry significantly impacts velocity distribution, causing skewed axial profiles.
- Observed strong secondary flow and vortex structures in in-plane velocity patterns.
- Found lower, more uniform WSS at the anastomosis compared to higher, localized WSS in the bypassed artery.
Conclusions:
- The nonplanar geometry of CABG and inflow conditions substantially affect graft hemodynamics.
- Understanding these fluid mechanics is crucial for improving CABG patency and reducing failure.
- Detailed 3D modeling provides critical insights into factors influencing graft success.
Abstract:
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.
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