Myocardial material parameter estimation: a comparison of invariant based orthotropic constitutive equations

Area of Science:

• Biomedical Engineering
• Computational Mechanics
• Cardiovascular Research

Background:

• Passive myocardial tissue exhibits complex mechanical behavior crucial for cardiac function.
• Accurate constitutive models are essential for simulating cardiac mechanics and understanding disease.
• Previous models based on Green strain and microstructural laws have limitations in fitting experimental data.

Purpose of the Study:

• To investigate invariant-based orthotropic and transversely isotropic constitutive equations for passive myocardial tissue.
• To evaluate the suitability of recently proposed functional forms against experimental simple shear data.
• To compare constitutive laws based on goodness of fit and parameter variability.

Main Methods:

• Applied invariant-based orthotropic and transversely isotropic constitutive relations.
• Utilized a dataset of three-dimensional simple shear mechanics data from passive myocardial tissue.
• Compared model performance using goodness of fit criteria for six shear deformation tests.
• Assessed parameter variability to determine model robustness.

Main Results:

• Invariant-based orthotropic and transversely isotropic constitutive laws were evaluated.
• A specific polyconvex type law demonstrated high suitability.
• The exponential Fung-type law also showed excellent performance in fitting shear data.
• Both identified laws proved most effective for modeling orthotropic myocardial behavior.

Conclusions:

• The Fung-type and polyconvex constitutive laws are highly suitable for modeling passive myocardial tissue under simple shear.
• These models offer improved accuracy and robustness for representing cardiac tissue mechanics.
• The findings contribute to more precise computational models of the heart.