Case Studies of the Human Cardiovascular System - Computational Hemodynamics: Theory, Modelling and Applications - page 208

Table 7.5 Maximum wall shear stress comparison among ten case studies. Comparison among
patients is carried out with the maximum wall shear stress (WSS max ) values presented in descend-
ing order. Subject (6) experiences the maximum WSS at the ECA branch. Based on the geometry
comparison, we know that subject (6) has a severe stenosis at the ECA of the carotid bifurcation
Locations and values of maximum WSS
Patients Locations WSS max (Pa)

(6) ECA branch 370

(4/L) CCA near bifurcation 239

(1/R) ICA branch 184

(2/L) ICA branch 150

(1/L) ICA branch 144

(5/R) Bifurcation and ECA branch 123

(4/R) ICA branch 113

(5/L) Bifurcation and ECA branch 91

(2/R) ICA branch 65.5

(3) ICA branch 53.5

7.3.3.2 Wall Shear Stress at CCA, ICA and ECA Sections

Planes on the CCA, ICA and ECA of five selected subjects were used for analysis.
Wall shear stresses are calculated and compared with each other (Fig. 7.21 ). The
ECA and ICA sections are selected at the stenosed location (at place of smallest di-
ameters), while the CCA sections are selected at a common location that is typically
located at approximately three times the CCA diameter below its bifurcation. The
wall shear stress is chosen at peak systole.
No common trend exists for the patients. Based on the CCA planes of the five
subjects, values of WSS for (1/L), (2/L) and (3) vary more than those for (1/R) and
(2/R). For example, the maximum WSS for patient (1/L) is 14 Pa and its minimum
value is 0 Pa, which results in a difference of 14 Pa. But WSS that pertains to case
subject (1/R), which ranges from 2.8 to 9 Pa, has a difference of 6.2 Pa. This may be
the result of large geometry change in cross sectional area for patient (1/L).

7.3.4 Comparison of Haemodynamic Properties

Carotid bifurcations of patients (1/L), (1/R), (2/L), (2/R) and (3) were investigated
for their geometrical and flow properties. These properties are given in Table 7.6 .
Note that D x and D y are the diameters of the vessel in the x - and y - orientations.
The ECA of patient (1/R) experiences maximum blood flow velocity (denoted as
Max Velocity) at 3.34 ms −1 as it has the smallest D x and D y values. The minimum
and maximum wall shear stresses, which are denoted as Min WSS and Max WSS
respectively, are given along with the angle that they occur in the radial orienta-
tion. For model (1/L), the values of these properties at the ECA section are Min