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Sun et al. Vessel Plus 2020;4:13 I http://dx.doi.org/10.20517/2574-1209.2020.02 Page 9 of 13

Figure 6. Scatter plot showing the correlation between peak stress and relative magnitude of the wall thickness in males and females with
abdominal aortic aneurysm (into the plane of the wall thickness - maximum diameter)

This conclusion was consistent in both types of models for males and females. When the asymmetry index
corresponded to 0.44 and the wall thickness to 2 mm, AAAs featuring maximum diameters of 5 cm for
[20]
women and 5.5 cm for men had comparable risk of rupture. Similarly, according to Forbes et al. , AAAs
with maximal values of 5.2 cm for females and 5.5 cm for males presented a comparable risk. However,
when the asymmetry index and wall thickness change, the peak stress of the AAA does the same, which
[37]
[20]
means that the conclusions of Forbes et al. are not applicable in all cases .
To more accurately reflect the relative magnitude of the risk of rupture in AAA, a range of values were
selected for each variable in the models designed for males and females (a maximum diameter from 3 cm
to 5 cm, an asymmetry index from 0.3 to 1, and a wall thickness from 0.8 mm to 2.2 mm) to determine
their intersection. Eleven discrete points were uniformly taken within the variation range of each factor,
and the dimensions were unified. Then, a scatter [Figure 6] and a 3D mesh [Figure 7] plots were obtained.
As presented in Figure 6, the plot is projected onto the plane of the wall thickness-maximum diameter. It
can be seen that the distribution trend of the points is obvious and there was no scatter in space. For AAAs
featuring the same maximum diameter, PWS > PWS female occurred when the vascular wall was thin and
male
the asymmetry index was large, or when the former was thick and the latter was small.

DISCUSSION
Traditionally, the maximum diameter of AAA has generally been used as a criteria for surgical treatment.
Increasingly however, clinical studies have suggested a deficiency in this maximal transverse measurement,
with greater consideration of morphology parameters in risk assessment of AAA over the last decades.
In recent years, studies have revealed that male and female differences were also important and should
be evaluated [19,20,25] . In the present study, both sex differences and morphological factors were considered
concurrently in predicting AAA rupture in high-risk patients. Nevertheless, it is of paramount importance
to include biomechanical assessment of the structures involved in AAA for a more thorough evaluation.
[38]
Collagen composition in the wall of AAAs in men and women are similar exception for its cross-linking
but the risk of rupture is multifactorial from a biomechanical point of view [39,40] . Sex affects AAA formation
but the role of hormones is still poorly understood.

Based on a series of numerical FSI simulations that considered patient sex and morphological factors