THE CLOSING VELOCITY OF MECHANICAL HEART-VALVE LEAFLETS

The closing motion of the occluder leaflets in bileaflet type mechanic al heart valves (MHV) runs monitored with a laser sweeping technique. The angular displacements of the leaflets were registered with precisi on of 0.2 mu s steps. Experimental measurements were made using five 2 9 mm Edwards-Duromedics(TM) including three original specification (ED OS) and two modified specification (EDMS), and two 29 mm St Jude Medic al(R) MHVs. The testing valve was installed in the mitral position of a physiologic pulsatile mock circulatory flow loop using water-glyceri ne solution as the testing fluid. Each valve was tested by: (1) direct mounting the valve on metal washers, and (2) mounting the valve with its sewing ring. Experiments were carried out al pulse rates of 70, 90 , and 120 beats min(-1), with the corresponding cardiac output of 5, 6 , and 7.5 litres min(-1), and maximum left ventricular pressure gradie nts (dp/dt) of 1,800, 3,000 and 5,600 mm Hg s(-1), respectively. The m axi,mum leaflet closing velocity of each of the tested valve types are presented. The difference in leaflet closing movements between the di rect rigid mounting and the sewing ring mounting are discussed. The de tails of the laser sweeping technique are presented.