Human thoracic and abdominal aortic aneurysmal tissues: Damage experiments, statistical analysis and constitutive...

Area of Science:

• Biomedical Engineering
• Cardiovascular Research
• Materials Science

Background:

• Aortic aneurysm development involves significant tissue remodeling, including increased collagen, reduced elastin, and smooth muscle cell degeneration.
• These morphological changes are hypothesized to alter the passive mechanical properties of the aortic wall.

Purpose of the Study:

• To quantify the impact of morphological changes on the passive mechanical response of thoracic and abdominal aortic aneurysms.
• To investigate tissue anisotropy and softening behavior under supra-physiological loading.
• To compare mechanical properties between healthy and diseased aortic tissues, and between thoracic and abdominal aneurysms.

Main Methods:

• Uniaxial extension tests were performed on circumferential and axial strips from human thoracic and abdominal aortic aneurysms.
• An anisotropic pseudo-elastic damage model was used to fit the mechanical testing data.
• Statistical analysis was used to compare model parameters between different tissue groups and to assess correlations with clinical factors.

Main Results:

• Aortic aneurysm tissue exhibits anisotropic mechanical behavior.
• The anisotropic pseudo-elastic damage model accurately describes primary loading and discontinuous softening, interpreted as tissue damage.
• Statistically significant differences in model parameters were found between diseased thoracic and abdominal tissues, and between healthy and diseased tissues.
• Body Mass Index (BMI) showed a correlation with model parameters in abdominal aortic aneurysms.

Conclusions:

• Morphological changes in aortic aneurysms significantly alter passive mechanical properties, with distinct differences observed between thoracic and abdominal tissues.
• The developed damage model effectively captures the mechanical response and softening of aneurysmal tissue.
• Understanding these mechanical differences is crucial for characterizing aneurysm progression and informing treatment strategies.