# Evaluating the Stress State and the Load-Bearing Fraction as Predicted by an In Vivo Parameter Identification Method for the Abdominal Aorta

## TL;DR

This study evaluates a method for predicting stress and load in the abdominal aorta, finding it works well under certain conditions but has limitations.

## Contribution

The study introduces an in vivo parameter identification method validated through in silico experiments for arterial mechanics.

## Key findings

- The circumferential stress state is well represented in aorta models with low transmural stress gradients.
- Collagen-attributed load-bearing fraction predictions are accurate, especially in the circumferential direction.
- Discrepancies increase with higher transmural stress gradients due to model limitations in capturing these gradients.

## Abstract

Background: Arterial mechanics are crucial to cardiovascular functionality. The pressure–strain elastic modulus often delineates mechanical properties. Emerging methods use non-linear continuum mechanics and non-convex minimization to identify tissue-specific parameters in vivo. Reliability of these methods, particularly their accuracy in representing the in vivo stress state, is a significant concern. This study aims to compare the predicted stress state and the collagen-attributed load-bearing fraction with the stress state from in silico experiments. Methods: Our team has evaluated an in vivo parameter identification method through in silico experiments involving finite element models and demonstrated good agreement with the parameters of a healthy abdominal aorta. Results: The findings suggest that the circumferential stress state is well represented for an abdominal aorta with a low transmural stress gradient. Larger discrepancies are observed in the axial direction. The agreement deteriorates in both directions with an increasing transmural stress gradient, attributed to the membrane model’s inability to capture transmural gradients. The collagen-attributed load-bearing fraction is well predicted, particularly in the circumferential direction. Conclusions: These findings underscore the importance of investigating both isotropic and anisotropic aspects of the vessel wall. This evaluation advances the parameter identification method towards clinical application as a potential tool for assessing arterial mechanics.