New generation tissue valves. Their in vitro function in the mitral position

The in vitro function of six tissue valves from four manufacturers has been assessed. One porcine bioprosthesis (Carpentier-Edwards supra-annular) and five pericardial valves (Edwards, Hancock, Ionescu-Shiley, Ionescu-Shiley low-profile, and Mitral Medical Mitroflow) were tested. Valve function was measured in a pulse duplicator simulating conditions of sinus rhythm (60, 80, and 120 beats/min and stroke volume 70 ml) and supraventricular tachycardia (200 beats/min and stroke volume 30 ml). Under each of these test conditions, mean transvalvular pressure, regurgitation, and transvalvular energy loss were determined and used to compare valve function. The porcine valve showed the largest mean transvalvular pressure during forward flow. The total energy loss of this valve, however, was not the largest for the valves tested. The total transvalvular energy loss ranged between 3% and 12% for all valves and conditions. For all valves, energy loss and regurgitation were greatest during simulated tachycardia.