Design of a fourth generation prosthetic heart valve: tri-leaflet valve

ESQUIVEL, C. M.; MARIO ROBERTO ROSENBERGER; GUEIJMAN, S. F.; SCHVEZOV, C. E.; AMERIO, O. N.

www.fac.org.ar/tcvc

Congreso; Third Congress of Cardiology on the Internet; 2003

Facultad de Bioingeniería UN.de Entre Rios

Introduction: The interest in developing a prosthetic heart tri-laeflet valve is based on the durability of mechanical prosthesis; the good hemodynamic performance of bio-prosthesis due to the central flow, its perfect closure, the negligible thrombogenic index, and the negligible perception of its presence by the user. Objectives: Develop a mathematical model of a fourth generation prosthetic heart valve or tri-leaflet valve. Obtain an optimal design through numerical modeling using computational fluid dynamics. Modeling procedure: Tri- and Bi-leaflet valves were designed schematically. Each model valve was situated in the center of a cylindrical tube. The fluid was assumed to be incompressible, newtonian, isothermal and stationary. Meshing and Finite Element modeling was performed using Gambit(R) 1.2 and Fidap(R) 8.5 from Fluent Inc. The model was validated mathematically comparing our results with the results available in the literature for bi-leaflet prosthesis. Results: The flow in the tri-leaflet valve is mainly central, with an 86% to 95% of the total flow. The effective surface area for flow is 67.4% of the total section, 32.6% of the surface area is obstructed by pivot system (11%) and the leaves (21.6%). The shear stresses are lower than the values reported as lower limit for hemolysis by foreign bodies.  Discussion: The amount of central flow in the tri-leaflet valve is high, similar to the center flow in natural valves and much higher than in a bi-leaflet valve. The design based in peripheral pivots gives good aperture characteristics that avoid the immobilization of the leaves by invasive tissue. The flow under maximum aperture is affected mainly by the pivot systems and the curvature of the leaves. Conclusions: Modeling results of a tri-leaflet valve indicate the presence of a high amount of central flow. The design may be improved by modeling modifying the pivot systems and the curvature of the leaves.