ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

of re-stenosis in either of the anastomoses. This configuration (illustrated in Fig.1a)
brings about a less disturbed flow environment compared to other modified ETS
anastomosis designs. In our previous study, the vessel walls were assumed to be rigid
and the blood was taken to be a Newtonian fluid [6], and by varying the design
parameters of the anastomotic angle and distance between the two anastomoses, the
superior coupled side-to-side (STS)–ETS anastomoses design was found to have the
anastomotic angle of 30° and 30 mm distance between the two (STS and ETS)
anastomoses.
There are some debates as to the necessity for undertaking the fluid–structure
interaction (FSI) investigations when examining the flow fields in coronary arteries, and
the findings of relatively small diameter variations raises questions regarding the
influence of wall deformation on the WSS behavior. There is no consensus on the
significance of the effect of the wall compliance on the flow field and hemodynamic
parameters. Some researchers have concluded that FSI analysis is indispensable for
realistic simulation of the flow field in the coronary artery [7], while some others have
indicated that the effect of arterial wall deformation on arterial flow can be insignificant
[8]. Therefore, we have undertaken this study primarily in the light of estimating the
significance of vessel wall compliance effect on HPs distribution in our CABG coupled
SQA design (shown in Fig.1a). Further, the effect of non-Newtonian rheology is
investigated in this novel SQA configuration. These effects are investigated in the
superior SQA model and its corresponding conventional ETS model (shown in Fig.1b)
to verify the previously observed advantages of this novel coupled sequential CABG
design over the conventional ETS configuration in a more realistic bio-mechanical
condition. For this purpose, the transient wall equations and the flow equations are
solved in an implicitly coupled approach, using an iterative procedure.
S1 S2 S3
P1
L P L STS
S4 S5
Fig.1. (a): Coupled STS-ETS sequential anastomoses model. S1 to S10 and P1 to P7 indicate,
respectively, the cross sections and the points at which velocity profiles and WSS variations are
discussed. (b): Conventional ETS anastomosis model.
3. MATERIALS AND METHODS
d
P2
P6
P7 P8
S6 S7 P3 S8 P4 S9 P5 S10
L ETS
L L P L D ETS L D
A two-way (bi-directional) FSI simulation of blood flow in compliant-wall CABG
models is conducted using the commercial computational software ANSYS Workbench
(ANSYS Inc.) for the coupling of the finite-element-based software, ANSYS, with the
finite-volume-based software, ANSYS CFX. Therein, the calculated displacements of
the solid (vessel) structure are transferred to the boundary walls of the fluid domain and
the computed forces in CFX are sent back to the solid domain during each stagger
(coupling) iteration.
(a)
(b)