Layer- and region-specific material characterization of ascending thoracic aortic aneurysms by microstructure-based...

Area of Science:

• Biomedical Engineering
• Materials Science
• Cardiovascular Research

Background:

• Ascending thoracic aortic aneurysms (ATAA) require material characterization to understand rupture mechanisms.
• Few studies have detailed layer- and region-specific wall properties in ATAA.
• Accurate constitutive models are essential for predicting ATAA biomechanics.

Purpose of the Study:

• To implement microstructure-based formulations for ATAA wall property characterization.
• To derive collagen fiber orientation angles for constitutive model validation.
• To evaluate simplified constitutive models for computational efficiency.

Main Methods:

• Image-based analysis to determine collagen fiber orientation angles.
• Development and implementation of a four-fiber constitutive model with angle dispersions.
• Parametric analysis to compare a condensed model (without longitudinal fibers) against the four-fiber model.
• Testing model performance against biomechanical data from tensile testing.

Main Results:

• Histological observations revealed wide distributions of collagen fiber orientations.
• A four-fiber model successfully implemented biomechanical data.
• A condensed model (omitting longitudinal fibers) performed comparably to the four-fiber model.
• The condensed model offers advantages due to fewer parameters.
• A novel hypothesis suggests fibers can support compressive stresses, improving model fits.

Conclusions:

• Microstructure-based models enhance understanding of ATAA biomechanics.
• A simplified fiber-reinforced model provides accurate characterization with computational benefits.
• The hypothesis of fibers supporting compressive stress warrants further investigation for improved constitutive modeling of aortic tissue.