In vitro assessment of mitral valve prostheses.

The performance of five prosthetic mitral valves (Ionescu-Shiley, Hancock, Carpentier-Edwards, Starr-Edwards, and Björk-Shiley), all of the same nominal size (29 mm), has been assessed in a hydromechanical simulation of the left heart at three pulse rates. The mean and maximum transvalvular pressure differences, the observed and/or calculated area, and the energy loss for each valve were compared. It was found that each measure of performance rates the valves in the same order or merit, with the Ionescu-Shiley valve performing the best and the Hancock the worst among the valves tested.

Unsteady fluid dynamics of several mechanical prosthetic heart valves using a two component laser Doppler anemometer system.

Five typical mechanical heart valves (Starr-Edwards, Björk-Shiley convexo-concave (c-c), Björk-Shiley monostrut, Bicer-Val, and St. Jude Medical) were tested in the mitral position under the pulsatile flow condition. The test program included measurements of velocity and turbulent stresses at 5 downstream locations. The study was carried out using a sophisticated cardiac simulator in conjunction with a highly sensitive 2 component laser Doppler anemometer (LDA) system. The continuous monitoring of parametric time histories revealed useful details about the complex flow and helped to establish the locations and times of the peak parameter values. Based upon the nondimensional presentation of data, the following general conclusions can be made. First, all the 5 valve designs created elevated turbulent stresses during the accelerating and peak flow phases, presenting the possibility of thromboembolism and perhaps hemolysis. Second, the difference in valve configuration seemed to affect the flow characteristics; third, the bileaflet design of the St. Jude valve appeared to create a lower turbulence stress level.

On the hemodynamics of several prosthetic heart valves: in vitro study.

Distribution of velocity, viscous shear stress and turbulence intensity in the wake of several mechanical heart valves is studied using a laser Doppler anemometer system during steady and pulsatile flow conditions. The corresponding results are also obtained for a sharp-edged orifice which help assess changes in the flow pattern caused by different valve geometries. The results are correlated with the static pressure drop across the valves and its recovery in the wake, as a function of the Reynolds number. Results suggest a substantial increase in turbulence intensity, in some cases by as much as 40- to 50-fold, thus raising a possibility of thromboembolism.