Abstract: Methods for impregnating polymer beads comprise providing polymer beads in an impregnation chamber at a temperature from about 150.degree. F. to about 200.degree. F. and a pressure of from about 25 psig to about 100 psig, and simultaneously fluidising the polymer beads in the impregnation chamber with an impregnating gas. The gas is delivered to the chamber at a rate sufficient to cause individual polymer beads to be fluidised and for a time sufficient to impregnate the gas in the polymer beads. The apparatus adapted for such methods includes a heater, a compressor and a plurality of vents for supplying a gas to the impregnating chamber to fluidise polymer beads contained therein simultaneously with the heating and pressurising of the beads.

Abstract: A pivot mechanism for a mechanical heart prosthesis includes internal recesses on an inside surface of an orifice ring having portions thereof near the recesses tapered to reduce flow resistance and minimize turbulence to improve hemodynamic efficiency of the heart valve prosthesis, to reduce its hemolytic potential, and possibly reduce its thrombogenicity by having no regions of stasis within the recess. The pivot mechanism for the mechanical heart valve prosthesis enables contact between the entire length of tabs of the heart valve leaflets and the sides of the recesses when the leaflets are in both the fully open and fully closed positions. This increases the contact area between the tabs and the recesses, reducing the magnitude of the contact stresses and, therefore, improving the durability of the device.