Optimization of Coronary Artery Bypass Graft using CFD Simulation

This literature review explores the optimization of coronary artery bypass graft using CFD simulation for patients with coronary artery. It discusses the use of computational fluid dynamics in assessing hemodynamics, the principles of CFD, commercial packages available, and the errors in CFD simulation. The review also covers different configurations of coronary artery bypass graft and the challenges in the field. References are provided for further reading.

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Literature Review on Optimization of Coronary Artery Bypass Graft using CFD Simulation for
Patients with Coronary Artery
The waveform of the coronary artery velocity is based on the adherence of the heartbeat
and coronary artery. However such compliance is expected to be higher than that of the host to
affect the flow of blood in the graft. Often certain difficulties arise during the provision of a
solution to the fluid-structure interaction in the computational fluid dynamic (Kabinejadian et
al.2016 p.425). It was therefore assumed by certain numerical studies that the implications of the
coronary artery bypass graft deformation to the hemodynamic is non-vital and should, therefore,
be ignored.
Optimization is a process which entails the identification of a good available value of a
goal in a defined domain in a group of parameters and constraints. However, in relation to the
cardiovascular diseases, it is used to enhance the various methods of surgery and other design
medical equipment. The computational fluid dynamics is considered as one of the most effective
numerical mechanism which is used in the investigation of both the geometrical and physical
factors which affect the hemodynamic of different configurations of coronary artery bypass graft
(Ramachandra, Kahn and Marsden, 2016 p.285)
The use of the computational fluid dynamics in the optimization process allows for an
effective and accurate assessment of the bypass graft process. Such an effective process is
attained based on the fact that with the computational fluid dynamics, the cyclic flow, flow
characteristics, pressure, and the wall shear stress can easily be evaluated. Based on research
which was conducted recently, it was found out that the use of the computational fluid dynamics
in both the hemodynamic and biomechanics is a good alternative to the in vivo and in vitro
measurements which are time-consuming and expensive. Generally, the establishment of the

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computational fluid dynamics is done on the basis of three vital principles which include,
conservation of energy, Newton’s second law that is the rate change of momentum equal to the
sum of the forces and the conservation of mass (Randles, Frakes and Leopold, 2017 p.1055).
The above mentioned principles can, however, be expressed in mathematical equations to
get the final numerical results in time and space. Consequently, in the last few years, there has
been an increase in the application of the computational fluid dynamics and this is especially in
the consolidation with both the pure theoretical and physical measurement techniques. With such
an increasing demand for the computational fluid dynamics, there has been the introduction of a
variety of commercial packages in the market (Samyn and LaDisa, 2016 p.100). However such
packages are put in the market on the basis of accuracy degree and the physical problem at hand.
Examples of the packages include open CFD, comsol, tech analysis, flow science, and ANSYS.
The most accurate and precise commercial package has been considered as the ANSYS
workbench in which the element of finite volume is used in the provision of solutions to the
discretized equations which represents the structure deformations, blood flow, mass and heat
transfer among others. Often the fluid domain undergoes various changes with time which occurs
in the fluid-structure interaction problems in the blood flow in an artery (Tröbs et al.2016 p.33).
Moreover, the element of a mesh is used in the fulfillment of the boundary condition. Often the
accurate numerical results relate directly to the mesh quality which has been adopted in the
computational fluid dynamics. The optimization of time, accuracy and number of elements for
simulation depends on a variety of techniques of meshing which are made available. The types of
meshing are usually based on the shape of the element. The key examples of types of meshing
include, triangle, quadrilateral, tetrahedral, hexahedral and surface meshing among others and
they have different shapes of an element such as 2D and 3D.

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There are typically numerous errors in the computational fluid dynamic simulation. For
some time, the technique has been applied by a variety of engineers and researchers. One of the
vital advantages of the technique is that it can provide accurate solutions to the Navier Stokes
equations which manually are hard to solve (Gutierrez e tall.2017 p.3). Despite that, there are
certain elements which the technique has been able to solve such as multiphase flow,
combustion, and turbulence. There has been no solution to the above mentioned elements due to
lack of reality resulting in certain potential errors in the computational fluid dynamic. The
different errors include application, meshing, user, software and numerical errors among others.
The possible errors can be minimized. However, a lot of time and cost will be required to get a
permanent solution. Consequently, the engineers and researchers have found a way to weigh
between cost and time taken on one hand and the approximate numerical results errors on the
other hand. To increase the accuracy and confidence in the numerical results, a validation of the
results are often carried out.
According to Douglas et al. (2015 p.3360), during the optimization process, there are
various ways of configuring the CARB such as an end to end anastomosis and side to side
anastomosis. The end to end is often used when the bypass conduit is short hence cannot reach
the diseased site. Additionally, the side to side configuration is applied in between the
intermediate coronary artery and the mid portion of the vein graft. Apart from the above
mentioned configuration techniques, the other method is the end to side configuration which is
the most common and researched. It works by redirecting the flow of blood into another side
close to the blocked artery by placing the bypass graft over the blockage.
The main aim of the approach entails the use of advanced individual conduit to bypass a
variety of coronary arteries. However, just like the end to end configuration, there is often a

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failure in relation to graft outcome which is due to the development of the atherosclerotic disease
(Ballarin et al.2016 p.615). Despite the many literature publications on the hemodynamics of
coronary artery bypass graft including other factors influencing the establishment of the intimal
hyperplasia, there are no complete guideline and an updated trend in myocardial
revascularization field. Additionally, there is inadequate knowledge on the fluid-structure
interactions and the adherence mismatch, especially for the small diameter arteries.

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References
Ballarin, F., Faggiano, E., Ippolito, S., Manzoni, A., Quarteroni, A., Rozza, G. and Scrofani, R.,
2016. Fast simulations of patient-specific haemodynamics of coronary artery bypass grafts based
on a POD–Galerkin method and a vascular shape parametrization. Journal of Computational
Physics, 315, pp.609-628.
Douglas, P.S., Pontone, G., Hlatky, M.A., Patel, M.R., Norgaard, B.L., Byrne, R.A., Curzen, N.,
Purcell, I., Gutberlet, M., Rioufol, G. and Hink, U., 2015. Clinical outcomes of fractional flow
reserve by computed tomographic angiography-guided diagnostic strategies vs. usual care in
patients with suspected coronary artery disease: the prospective longitudinal trial of FFRCT:
outcome and resource impacts study. European heart journal, 36(47), pp.3359-3367.
Gutierrez, N.G., Kahn, A., Burns, J.C. and Marsden, A.L., 2017. Computational blood flow
simulations in Kawasaki disease patients: Insight into coronary artery aneurysm
hemodynamics. Global cardiology science & practice, 2017(3).
Kabinejadian, F., Ghista, D.N., Nezhadian, M.K. and Leo, H.L., 2016. Hemodynamics of
coronary artery bypass grafting: conventional vs. innovative anastomotic configuration designs
for enhancing patency. In Coronary Graft Failure (pp. 419-436). Springer, Cham.
Ramachandra, A.B., Kahn, A.M. and Marsden, A.L., 2016. Patient-specific simulations reveal
significant differences in mechanical stimuli in venous and arterial coronary grafts. Journal of
cardiovascular translational research, 9(4), pp.279-290.

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Randles, A., Frakes, D.H. and Leopold, J.A., 2017. Computational Fluid Dynamics and Additive
Manufacturing to Diagnose and Treat Cardiovascular Disease. Trends in biotechnology, 35(11),
pp.1049-1061.
Samyn, M.M. and LaDisa, J.F., 2016. Novel Applications of Cardiovascular Magnetic
Resonance Imaging-Based Computational Fluid Dynamics Modeling in Pediatric Cardiovascular
and Congenital Heart Disease. In Assessment of Cellular and Organ Function and Dysfunction
using Direct and Derived MRI Methodologies. InTech.
Tröbs, M., Achenbach, S., Röther, J., Redel, T., Scheuering, M., Winneberger, D., Klingenbeck,
K., Itu, L., Passerini, T., Kamen, A. and Sharma, P., 2016. Comparison of fractional flow reserve
based on computational fluid dynamics modeling using coronary angiographic vessel
morphology versus invasively measured fractional flow reserve. The American journal of
cardiology, 117(1), pp.29-35.