Validation of numerical simulation with PIV measurements for two anastomosis models
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Published on: July 19, 2016
Jun-Mei Zhang1, Leok Poh Chua, Dhanjoo N Ghista
1School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore 639798, Singapore.
Insights
A 135-degree proximal anastomosis model for coronary artery bypass grafts (CABG) may reduce stenosis risk compared to a 90-degree model. This is due to more favorable hemodynamic parameters, potentially lowering intimal thickening and atherosclerosis.
Area of Science:
- Cardiovascular Surgery
- Biomedical Engineering
- Fluid Dynamics
Background:
- Coronary artery bypass graft (CABG) stenosis is influenced by hemodynamics.
- Proximal anastomosis in CABG requires further investigation regarding stenosis.
- Flow dynamics at the proximal anastomosis may impact stenosis initiation and progression.
Purpose of the Study:
- To investigate hemodynamic differences between 90-degree and 135-degree proximal anastomosis models for CABG.
- To validate numerical simulations of proximal anastomosis flow characteristics with experimental data.
- To assess the potential of different anastomosis angles in mitigating stenosis and atherosclerosis.
Main Methods:
- Designed and constructed 90-degree and 135-degree anastomotic models for CABG simulation.
- Employed Particle Image Velocimetry (PIV) measurements on Pyrex glass models.
- Validated numerical simulation results against experimental flow characteristics, velocity profiles, and wall shear stress (WSS).
Main Results:
- Observed good agreement between numerical and experimental data for flow characteristics, velocity profiles, and WSS.
- Identified disturbed flow patterns including stagnation points, flow separation, and vortices in both models.
- Numerical analysis indicated the 135-degree model potentially reduces intimal thickening and atherosclerosis risk compared to the 90-degree model.
Conclusions:
- The 135-degree proximal anastomosis model shows promise for reducing CABG stenosis.
- Lower variation in time-averaged WSS and segmental average of WSSG in the 135-degree model suggest reduced atherosclerotic potential.
- Hemodynamic factors at the proximal anastomosis are critical for graft patency and long-term outcomes.
Abstract:
Hemodynamics is widely believed to influence coronary artery bypass graft (CABG) stenosis. Although distal anastomosis has been extensively investigated, further studies on proximal anastomosis are still necessary, as the extent and initiation of the stenosis process may be influenced by the flow of the proximal anastomosis per se. Therefore, in this study, two models (i.e. 90 degrees and 135 degrees anastomotic models) were designed and constructed to simulate a proximal anastomosis of CABG for the left and right coronary arteries, respectively. Flow characteristics for these models were studied experimentally in order to validate the simulation results found earlier. PIV measurements were carried out on two Pyrex glass models, so that the disturbed flow (stagnation point, flow separation and vortex) found in both proximal anastomosis models using numerical simulation, could be verified. Consequently, a fair agreement between numerical and experimental data was observed in terms of flow characteristics, velocity profiles and wall shear stress (WSS) distributions under both steady and pulsatile flow conditions. The discrepancy was postulated to be due to the difference in detailed geometry of the physical and computational models, due to manufacturing limitations. It was not possible to reproduce the exact shape of the computational model when making the Pyrex glass model. The analysis of the hemodynamic parameters based on the numerical simulation study also suggested that the 135 degrees proximal anastomosis model would alleviate the potential of intimal thickening and/or atherosclerosis, more than that of a 90 degrees proximal anastomosis model, as it had a lower variation range of time-averaged WSS and the lower segmental average of WSSG.
