An Octahedral Fibrous Constitutive Model for Heart Valve Mechanics and Function

Area of Science:

• Biomechanics
• Biomaterials Science
• Computational Biology

Background:

• Fibrous soft tissues exhibit complex nonlinear mechanical behavior due to extracellular matrix fiber networks.
• Fiber organization dictates key properties like strain stiffening, reverse Poynting effect, and anisotropy.

Purpose of the Study:

• Develop an anisotropic hyperelastic model for fibrous biological tissues, considering fiber network contributions under tension and compression.
• Calibrate the model to experimental data from mitral valve leaflets using inverse finite element analysis and automatic differentiation.
• Investigate the impact of anisotropy and fiber reorientation on mitral valve deformation during physiological loading.

Main Methods:

• Developed a novel anisotropic hyperelastic constitutive model for fibrous tissues.
• Employed an inverse finite element approach coupled with automatic differentiation for model calibration.
• Utilized experimental data from mitral valve leaflets for validation.

Main Results:

• Model calibration demonstrated the importance of fiber network contributions.
• Leaflet compliance in the radial direction is crucial for proper valve closure.
• Localized fiber reorientation causes stress concentrations, potentially leading to functional degradation.
• Circumferential-dominant compliance compromises valve closure, resulting in mitral regurgitation.
• Chordal softening exacerbates the severity of mitral regurgitation.

Conclusions:

• Fiber architecture alterations significantly impact mitral valve mechanics and function.
• Changes in fiber organization, particularly with chordal degradation, can initiate and progress mitral valve incompetence.
• The developed model provides insights into the relationship between tissue microstructure and macroscopic mechanical behavior.