Background
Abdominal aortic aneurysms (AAAs) are currently treated based on the universal maximum
diameter criterion, but other geometric variables may play a role in the risk of rupture.
The hemodynamic environment inside the AAA sac has been shown to interact with several
biologic processes which can affect prognosis. AAA geometric configuration has a significant
impact in the hemodynamic conditions that develop, which has only been recently realized,
with implications for rupture risk estimations. We aim to perform a parametric study
to evaluate the effect of aortic neck angulation, angle between the iliac arteries,
and sac asymmetry (SA) on the hemodynamic variables of AAAs.
Methods
This study uses idealized AAA models and it is parametrized in terms of 3 quantities
as follows: the neck angle, φ (°), iliac angle, θ (°), and SA (%), each of which accepts 3 different values, specifically φ = (0°,
30°, 60°), θ = (40°, 60°, 80°), and SA = (S, °SS, °OS), where the SA can either be on the same
side with respect to neck (SS) or on the opposite side (OS). Time average wall shear
stress (TAWSS), oscillatory shear index (OSI), relative residence time (RRT), and
the velocity profile are calculated for different geometric configurations, while
the percentage of the total surface area under thrombogenic conditions, using thresholds
previously reported in the literature, is also recorded.
Results
In case of an angulated neck and a higher angle between iliac arteries, favorable
hemodynamic conditions are predicted with higher TAWSS and lower OSI and RRT values.
The area under thrombogenic conditions reduces by 16–46% as the neck angle increases
from 0° to 60°, depending on the hemodynamic variable under consideration. The effect
of iliac angulation is present but less pronounced with 2.5–7.5% change between the
lower and the higher angle. The effect of SA seems to be significant for OSI, with
a nonsymmetrical configuration being hemodynamically favorable, which in the presence
of an angulated neck is more pronounced for the OS outline.
Conclusions
Favorable hemodynamic conditions develop inside the sac of idealized AAAs with increasing
neck and iliac angles. Regarding the SA parameter, asymmetrical configurations most
often appear advantageous. Concerning the velocity profile the triplet (φ, θ, SA) may affect outcomes under certain conditions and thus should be taken into account
when parametrizing the geometric characteristics of AAAs.
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Article info
Publication history
Published online: March 01, 2023
Accepted:
February 14,
2023
Received:
November 10,
2022
Publication stage
In Press Journal Pre-ProofFootnotes
Funding: None.
Conflict of interest: None.
Identification
Copyright
© 2023 Elsevier Inc. All rights reserved.
