A lumped parameter model to evaluate the fluid dynamics of different coronary bypasses
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Published on: February 13, 2021
R Pietrabissa1, S Mantero, T Marotta
1Dipartimento di Bioingegneria, Politecnico di Milano, Italy.
Insights
Mathematical models of coronary artery bypass grafting show the internal mammary artery graft offers better hemodynamics than saphenous vein grafts. Sequential bypasses improve proximal flow but may reduce distal performance, impacting long-term graft patency.
Area of Science:
- Cardiovascular Physiology
- Biomedical Engineering
- Computational Fluid Dynamics
Background:
- Coronary artery bypass grafting (CABG) is crucial for myocardial reperfusion in severe coronary stenoses.
- Graft choice (internal mammary artery vs. saphenous vein) and configuration (single vs. sequential) significantly impact post-surgical coronary hemodynamics.
- Hemodynamic factors influence graft patency and may promote long-term atherogenic processes.
Purpose of the Study:
- To develop and validate an improved mathematical model of the cardiovascular system, specifically detailing the coronary tree.
- To simulate and analyze hemodynamic performance of different coronary artery bypass grafting configurations.
- To assess the impact of graft type and configuration on flow dynamics and wall shear stress.
Main Methods:
- A closed-loop mathematical model of the cardiovascular system was enhanced with a detailed coronary tree description.
- Models for internal mammary artery and saphenous vein grafts were developed.
- Simulations included single and sequential grafts of both internal mammary artery and saphenous vein, alongside coronary stenoses.
Main Results:
- The single internal mammary artery graft demonstrated superior hemodynamics (flow rate, wall shear stress) compared to the single saphenous vein graft.
- Sequential bypasses exhibited improved hemodynamic performance in proximal coronary segments but reduced performance distally.
- Simulations predicted modifications in flow waveforms, velocities, shear stress, and flow distribution based on bypass configuration.
Conclusions:
- The developed mathematical model serves as a valuable tool for investigating coronary artery bypass grafting outcomes.
- Internal mammary artery grafts appear hemodynamically advantageous over saphenous vein grafts for single bypass configurations.
- Bypass configuration significantly alters coronary hemodynamics, influencing potential long-term graft health and requiring careful surgical planning.
Abstract:
Coronary bypass grafting is a surgical procedure frequently performed to obtain myocardial reperfusion downstream from severe coronary stenoses. Different surgical techniques may be adopted which include the use of graft made of internal mammary artery or saphenous vein, and the adoption of multiple or sequential bypasses for more than one stenosis. The haemodynamics of the surgically reconstructed coronary bed is strongly dependent on the bypass configuration and may induce atherogenic processes affecting the long-term potency of the bypass. We have improved a closed-loop mathematical model of the cardiovascular system including a more detailed description of the coronary tree which allows the calculation of the flow rate and pressure curves in all the vessels considered. Pathological situations, such as stenoses, have been simulated and investigated. Models of the internal mammary artery and of the saphenous vein have also been developed in order to simulate coronary artery bypasses. The four simulated bypass configurations have been the single saphenous vein, the sequential saphenous vein, the single internal mammary artery and the sequential internal mammary artery. Results of the simulations of the different bypass grafting configurations indicate that between single saphenous vein and single internal mammary artery the latter shows better haemodynamics both for the flow rate pattern and for the calculated wall shear stress. The sequential bypasses show better haemodynamics in comparison with the single bypass in the proximal segments and worse performance in the distal ones. The models may be applied as an investigative tool to evaluate actual cases of surgically treatable coronary stenoses. They can predict the modification in blood flow waveforms, mean velocities, shear stress and distribution of blood flow in the coronary branches as a function of the adopted bypass configuration.
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