Constitutive modeling of ascending thoracic aortic aneurysms using microstructural parameters.

Area of Science:

• Biomedical Engineering
• Cardiovascular Research
• Materials Science

Background:

• Ascending thoracic aortic aneurysm (ATAA) is linked to reduced biomechanical strength and disrupted collagen microarchitecture.
• Bicuspid aortic valve (BAV) associated ATAA may develop earlier than degenerative aneurysms in tricuspid aortic valve (TAV) patients due to distinct extracellular matrix.
• Understanding the biomechanics of ATAA is critical for predicting disease progression.

Purpose of the Study:

• To model the fiber-reinforced mechanical response of ATAA tissues from BAV and TAV patients.
• To assess the impact of anisotropic constitutive formulation on aortic wall stress distribution.
• To investigate the role of collagen fiber architecture in ATAA biomechanics.

Main Methods:

• Image analysis of collagen fiber dispersion and alignment in dissected aortic tissues.
• Tensile testing of aortic specimens.
• Numerical simulations using fiber-reinforced constitutive models.

Main Results:

• Both BAV-ATAA and TAV-ATAA tissues exhibit altered collagen fiber architecture compared to normal aorta.
• Collagen fiber distribution significantly influences wall stress distribution, more so than peak stress.
• Anisotropic modeling revealed distinct stress patterns in aneurysmal aortas.

Conclusions:

• Fiber-reinforced constitutive modeling is essential for accurate biomechanical predictions in ATAA.
• Collagen fiber defects are inherent to aneurysmal ascending aorta.
• Accurate modeling can lead to biomechanical indicators for distinguishing ATAA severity.