Relative performance of prosthetic heart valves based on power measurements

The in vitro steady and pulsatile flow results of tests of a series of valves are reported. Fifteen mechanical and two tissue valves from 23 mm to 27 mm nominal size from six manufacturers, plus two prototype experimental valves, were tested in the aortic position in a circulation system simulator. Steady-flow pressure drop/flow rate measurements were direct-recorded on an X-Y plotter. Pulsatile flow rate, LVP, AoP, pressure drop, and pressure-drop power were recorded. Input (left ventricle pumping) power was also recorded directly as the multiplier output from the product of flow rate and LVP. Results are presented in tables and graphs. Power loss at 70/min varied from 3% to 6%; backflow from 2.5% to 11%. Valve evaluation is based on the relative valve power loss that the heart must overcome. Backflow is shown to be as important as pressure drop in determining valve performance. A performance index (PI) equal to the percentage pressure-drop power loss plus the percentage backflow is presented as a means for performance rating. PI values from 6 to 17 were obtained on the 19 valves tested.