Advanced design of a mechanical prosthetic heart valve with three leaves and new haemocompatible materials,

AMERIO, O. N.; MARIO ROBERTO ROSENBERGER; SCHVEZOV, C. E.

Ottawa. Canadá

Congreso; 16thWorld Congress of the World Society of Cardio-Thoracic Surgeons.; 2006

WSCTS - University of Ottawa Heart Institute

Background: Design a mechanical prosthetic tri-leaflet valve with an optimal central flow closest to the flow of a native valve. Also, select the optimal material for building the designed valve considering the mechanical resistance, the haemocompatibility and availability of an accessible construction technology. Methods: The effect of the morphological design on the blood flow across the valve is studied employing computational fluid dynamic modeling with the finite element method. The fluid is assumed to be in steady state, uncompressible and with uniform viscosity; and the flow is analyzed for different blood flow rate. The results of the flow for a tri-leaflet valve (TLV) are compared with the flows obtained for a standard prosthetic bi-leaflet valve (BLV) and a native valve (NV). Results: The design of the TLV valve is an improvement of a previous TLV in which the shape, the position and rotate axis of the valves have been modified. The results for this TLV show the effective surface area for flow across the valve is 83.6% of the total valve section, compared to the 78.6% for the standard BLV. In addition 98% of the flow is central and the remaining flow goes through the peripheral section. For a stable flow of 5,000 cm3/min the pressure drop across the TLV is of 0.055 mmHg, considerably lower than the pressure droop for the BLV which is of 0.080 mmHg but higher than the calculated pressure droop for the native valve which is of 0.035 mmHg. The shear stress for the TLV is lower than for the BLV. With respect to the valve fabrication the material selected is a titanium alloy which is machined and coated with multilayer of titanium dioxide deposited by a sol-gel technique. In this way the good mechanical properties of the titanium alloy is combined with an oxide layer with a good haemocompatibility. This construction process is an accessible and suitable alternative among others like the Pyrolytic Carbon or Diamond-Like Carbon technologies. At present the sol-gel deposition process is being adjusted and optimized. Conclusions: The design of a tri-leaflet mechanical valve produces a mostly central flow, with less pressure droop across the valve and less shear stress than a bi-leaflet design. The construction procedure based in a body machined of a titanium alloy and then coated with titanium oxide by a sol-gel technique is a suitable alternative.