Abdominal aortic aneurysms (AAA) are an expansion in diameter of the
abdominal aorta and their rupture is a leading cause of mortality. One of the treatments
for AAA is the implantation of an endograft (also called a stent graft), a combination of
fabric and metal stents, to provide a new conduit for blood and shield the aneurysm sac
from direct pressurization. After implantation of the stent graft, the aneurysm may
shrink, grow, or stabilize in diameter ? even in the absence of apparent flow into the sac
? in some cases resulting in graft failure through component separation, kinking, or loss
of seal at its ends.
Greater understanding of AAA and treated AAA could provide insight on how
treatment might be modified to improve treatment methods and/or design devices to be
more effective in a wider range of patients. Computational models provide a means to
investigate the biomechanics of endografts treating AAA through analysis of the
endografts, the AAA, and the combination of them.
Axisymmetric models of endograft-treated AAA showed that peak von Mises
stress within the wall varied between 533 kPa and 1200 kPa when different material
properties for the endograft were used. The patient-specific models, built from time series of patient CT scans with similar patient history but different outcomes, show that
wall shrinkage and stability can be related to the level of stresses within the vessel wall,
with the shrinking AAA showing a greater reduction by endograft treatment and a lower
final value of average von Mises stress. The reduction in pressure felt by the wall is
local to the central sac region. The inclusion of thrombus is also essential to accurate
stress estimation.
The combination of axisymmetric and patient-specific computational models
explains in further detail the biomechanics of endograft treatment. The patient-specific
reconstruction models show that when effectively deployed and reducing the pressure
felt in the AAA wall, the graft is under tension in the sac region and compression at its
ends.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2009-05-716 |
| Date | 2009 May 1900 |
| Creators | Meyer, Clark A. |
| Contributors | Moore, James E. |
| Source Sets | Texas A and M University |
| Language | English |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | application/pdf |
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