Patient-specific initial wall stress in abdominal aortic aneurysms with a backward incremental method

Area of Science:

• Biomedical Engineering
• Computational Mechanics
• Cardiovascular Research

Background:

• Current abdominal aortic aneurysm (AAA) surgical criteria rely on maximum transverse diameter, which may not fully capture rupture risk.
• Patient-specific computational models are increasingly used for AAA analysis, but existing methods for wall stress calculation have limitations.

Purpose of the Study:

• To develop and validate a novel computational approach for calculating AAA wall stress that accounts for initial diastolic loading.
• To compare the accuracy of peak wall stress estimation between the new method and the conventional approach.

Main Methods:

• A backward incremental method was developed to compute wall stress on the true diastolic AAA geometry.
• The method was evaluated using a neo-Hookean material law and applied to patient-specific AAA geometries from cardiac-triggered MRI.
• Simulations were performed with both a basic and a more complex AAA-specific material law.

Main Results:

• The backward incremental method accurately predicts an unloaded configuration from loaded geometry and applied load.
• The conventional method, applying systolic pressure to the already loaded geometry, results in an underestimated peak wall stress and an unrealistic systolic shape.
• The novel approach yields a more plausible systolic aneurysm volume and a significantly different, more accurate peak wall stress estimate.

Conclusions:

• Incorporating initial diastolic stress into AAA wall stress simulations is crucial for accurate rupture risk assessment.
• The developed backward incremental method provides a more reliable estimation of peak wall stress and systolic geometry for patient-specific AAA.
• This refined computational approach can improve surgical decision-making for abdominal aortic aneurysms.