Experimental studies and computer modeling of viscoelastic properties of heart valve leaflets: Implication in heart valve tissue engineering

Diseased or damaged heart valve leaflets are amongst the major causes of illness and death globally. The currently available treatment of heart valve patients is to mend the damaged valves, but in most severe cases, heart valves require replacement since repair is not feasible. The survival of the patient, as well as implantation success rate, depends on the engineered heart valves to instantly ensure adequate mechanical support and function after surgery. Therefore, the engineered heart valves must demonstrate and preserve the biomechanical properties similar to those of native heart valves. In the current project, we aim to improve our understanding of the structural, mechanical and viscoelastic properties of heart valve leaflets. We aim to develop a new computational model for simulation of viscoelastic properties of heart valve leaflets. In the work reported here, native bovine heart valve leaflets were excised from bovine hearts, collected from local slaughter house in Beirut and cryopreserved as necessary. The oscillatory shear based viscoelastic properties were studied using a parallel plate rheometer. The critical parameters such as, modulus of elasticity, ultimate tensile strength, maximum elongation and the stress-strain relationships as well as the oscillatory shear properties were investigated. Furthermore, an FEM based tri-layer composite model is being developed for computational studies of heart valve viscoelastic properties using finite element code ABAQUS. The developed model will be validated against the rheological behavior obtained from experiments. The new model and the obtained results will provide significant insights into the correlations between the nano-microstructure and biomechanics of the heart valves and their macroscale behaviors under different healthy and pathological conditions. The proper understanding of the correlations between nano-biomechanics and pathological conditions can also pave the ways for generations of new therapeutics for various cardiovascular diseases.