ADVANCED DESIGN OF A MECHANICAL PROSTHETIC HEART VALVE WITH THREE LEAVES AND NEW HAEMOCOMPATIBLE MATERIALS

OSVALDO AMERIO, MARIO ROSENBERGER, CARLOS SCHVEZOV

Ottawa, Canada

Congreso; 16th World Congress World Society of Cardio-Thoracic Surgeons; 2006

World Society of Cardio-Thoracic Surgeons

Background: Design a mechanical prosthetic tri-leaflet valvewith an optimal central flow closest to the flow of a native valve.Also, select the optimal material for building the designed valveconsidering the mechanical resistance, the haemocompatibilityand availability of an accessible construction technology.Methods: The effect of the morphological design on the bloodflow across the valve is studied employing computational fluiddynamic modeling with the finite element method. The fluid isassumed to be in steady state, uncompressible and with uniformviscosity; and the flow is analyzed for different blood flow rate.The results of the flow for a tri-leaflet valve (TLV) are comparedwith 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 aprevious TLV in which the shape, the position and rotate axis ofthe valves have been modified. The results for this TLV show theeffective surface area for flow across the valve is 83.6% of thetotal valve section, compared to the 78.6% for the standard BLV.In addition 98% of the flow is central and the remaining flow goesthrough the peripheral section. For a stable flow of 5,000cm3/min the pressure drop across the TLV is of 0.055 mmHg,considerably lower than the pressure droop for the BLV which is of0.080 mmHg but higher than the calculated pressure droop forthe native valve which is of 0.035 mmHg. The shear stress for theTLV is lower than for the BLV. With respect to the valvefabrication the material selected is a titanium alloy which ismachined and coated with multilayer of titanium dioxidedeposited by a sol-gel technique. In this way the good mechanicalproperties of the titanium alloy is combined with an oxide layerwith a good haemocompatibility. This construction process is anaccessible and suitable alternative among others like the PyrolyticCarbon or Diamond-Like Carbon technologies. At present the solgeldeposition process is being adjusted and optimized.Conclusions: The design of a tri-leaflet mechanical valveproduces a mostly central flow, with less pressure droop across the valve and less shear stress than a bi-leaflet design. Theconstruction procedure based in a body machined of a titaniumalloy and then coated with titanium oxide by a sol-gel technique isa suitable alternative