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Wall stress and flow dynamics in abdominal aortic aneurysms: finite element analysis vs. fluid-structure interaction
Christine M Scotti1, Jorge Jimenez, Satish C Muluk
1Biomedical Engineering Department, Carnegie Mellon University, Pittsburgh, USA.
Summary
Fluid dynamics significantly impacts abdominal aortic aneurysm (AAA) wall stress, with flow analysis revealing up to 20% higher stress than static models. Aneurysm asymmetry and variable wall thickness further increase AAA wall stress.
Area of Science:
- Biomedical Engineering
- Cardiovascular Research
- Computational Fluid Dynamics
Background:
- Abdominal aortic aneurysm (AAA) rupture occurs when arterial wall strength is overcome by induced forces, often assumed to be uniform luminal pressure.
- Fluid dynamics and the interaction between blood flow and the arterial wall are critical factors in AAA pathogenesis.
- Current assessments often rely on simplified pressure estimations, potentially underestimating the mechanical stresses on the AAA wall.
Purpose of the Study:
- To evaluate the significance of assumed peak fluid pressure versus non-uniform pressure from fluid-structure interaction (FSI) in assessing AAA wall mechanics.
- To investigate the influence of asymmetry and variable wall thickness on AAA wall stress and fluid dynamics.
- To compare static pressure-deformation analysis with transient FSI analysis for AAA biomechanics.
Main Methods:
- Utilized a finite element approach to model ten idealized AAA geometries and one control.
- Incorporated five degrees of asymmetry and uniform/variable wall thickness.
- Performed both static pressure-deformation and transient fluid-structure interaction (FSI) analyses.
Main Results:
- Fluid flow inclusion increased maximum AAA wall stress by up to 20% compared to static analysis with assumed peak pressure (117 mmHg).
- Variable wall thickness models exhibited maximum wall stress nearly four times higher than uniform wall thickness models.
- Wall stress increased with greater asymmetry in both uniform and variable wall thickness models.
- Axial stretch and external pressure reduced wall stress by 17%.
Conclusions:
- Fluid-structure interaction (FSI) analysis provides a more accurate assessment of AAA wall mechanics than static pressure estimations.
- Aneurysm asymmetry and non-uniform wall thickness are critical factors that significantly elevate wall stress.
- Accurate modeling of AAA biomechanics requires consideration of dynamic blood flow and geometric variations.
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