Numerical simulation of hemodynamics frameless aortic valve bioprosthesis

This study describes an integrated approach biomechanics to modeling of a frameless prosthetic heart valve based on the analysis of medical graphic data (multispiral computed tomography), solid modeling (Abaqus/CAE) and numerical analysis of blood flow (OpenFOAM). The object of the study was the clinical case of patient D. (56 years old), who was surgically implanted with the “TiAra” aortic valve prosthesis. In this work, we reconstructed three-dimensional computer models of the functioning of the prosthesis for 10 segments of one cardiac cycle, followed by numerical experiments reproducing the movement of the key points of the product -commissural racks, leaflets. High asymmetric mobility of the bioprosthesis elements was shown during deformations of the heart cycle - one of the racks is much more mobile than the other two (up to 32% in movement). Solid modeling of the prosthesis deformation did not reveal significant malfunctioning or exceeding the stress-strain state of the components: Mises stress maximum reached 0.8 MPa. The distribution of stress indicators on the diagrams of three-dimensional models revealed the main concentration in the leaflet bell and commissural racks. In addition, qualitatively, the operation of the cusp apparatus corresponded to the functioning conditions - the dynamics of pressure changes in the structure of the cardiac cycle “systole-diastole”, area of cusps contact, and the elastic properties of the materials. The analysis of the flow simulation results determined the presence of several sections with a turbulent structure in the region of the Valsalva sinuses, which, however, did not demonstrate critical quantitative characteristics - wall shear stresses (up to 74 MPa), flow velocities (0.1-1.0 m/s).