An instrument for the measurement of in vitro velocity and turbulent shear stress in the immediate vicinity of prosthetic heart valves.

The measurements of velocity and turbulent shear stress in the immediate vicinity of prosthetic heart valves play a vital role in their design and evaluation. In the past, hot-wire/film and one-component laser Doppler anemometer (LDA) systems have been used extensively. Hot-wire/film anemometers, however, have some serious disadvantages, such as not being able to measure the directionality of the flow, disturbing the flow field with the probe, and requiring frequent calibration. One-component LDA systems do not have these problems, but they cannot measure turbulent shear stresses directly. Since these measurements are essential, and are not available in the open literature, a two-component LDA system was assembled to measure velocity and turbulent shear stress fields under pulsatile flow conditions. The experimental methodology used to create an in vitro data base of velocity and turbulent shear stress fields in the immediate vicinity of various designs of prosthetic heart valve in current clinical use is also discussed in this paper.