Study of Biomechanics of the Heart Valve Leaflet Apparatus Using Numerical Simulation Method.

The aim of the study was to study the complex biomechanics of the aortic valve prosthesis and to analyze the effect of frame mobility on the stress-strain state and geometry of the valve leaflet apparatus using a numerical simulation method, which reproduces the qualitative and quantitative results of its bench tests.

Materials and methods: The object of the study was a commercial valve bioprosthesis UniLine (NeoCor, Russia), a three-dimensional mesh of which was obtained on the basis of computer microtomography with a subsequent analysis of its stress-strain state in the systole- diastole cycle by the finite element method in the Abaqus/CAE medium. The simulation was validated by comparing the results of numerical and bench simulation on the ViVitro Labs hydrodynamic system (ViVitro Labs Inc., Canada).

Results: The method proposed in this study to simulate the mobility of commissural struts by including elastic connectors of adjustable stiffness in the calculation made it possible to reproduce the qualitative effects of the valve leaflet work observed in the bench experiment. The bioprosthetic orifice area in the systolic phase corresponded to the values obtained in the hydrodynamic system throughout the entire systole-diastole cycle. The analysis of the stress-strain state has shown the fundamental difference in the distribution of the von Mises stress fields depending on the numerical experiment design: the concentration of high amplitudes in the area of commissural struts and the central part of the free edge. However, quantitatively, the stress values reached the maximum of 0.850-0.907 MPa (0.141-0.156 MPa on average), which is below the ultimate strength of the biological material.

Conclusion: The results of this study with the validation performed allowed us to conclude that adequate results of modeling the biomechanics of the heart valve leaflet bioprosthesis based on the finite element method can be achieved by using a high-resolution model with the imposition of elastic connectors in the area of commissural struts. Taking into account the mobility of the frame struts of the heart valve prosthesis is decisive in relation to the final geometry of the valve apparatus and can act as a negative factor in case of a highly elastic material of the valve apparatus. The simulation method presented can be used to optimize the leaflet apparatus geometry of heart valve prostheses from the standpoint of assessing the distribution of the stress-strain state.