Integrating particle image velocimetry and laser Doppler velocimetry measurements of the regurgitant flow field past mechanical heart valves

This study investigates the transient regurgitant flow downstream of a pros thetic heart valve using both laser Doppler velocimetry (LDV) and particle image velocimetry (PIV). Until now, LDV has been the more commonly used too l in investigating the now characteristics associated with mechanical heart valves. The LDV technique allows point-by-point velocity measurements and provides enough information about the temporal variations in the flow. The main drawback of this technique is the time consuming nature of the data ac quisition process in order to assess an entire flow field area. The PIV tec hnique, on the other hand, allows measurement of the entire flow field in s pace in a plane at a given instant. In this study, PIV with spatial resolut ion of 0 (1 mm) and LDV with a temporal resolution of 0 (1 ms) were used to measure the regurgitant flow proximal to the Bjork-Shiley monostrut (BSM) valve in the mitral position. With PIV, the ability to measure 2 velocity c omponents over an entire plane simultaneously provides a very different ins ight into the flow field compared to a more traditional point-to-point tech nique like LDV. In this study, a picture of the effects of occluder motion on the fluid flow in the atrial chamber is interpreted using an integration of PIV and LDV measurements. Specifically, fluid velocities in excess of 3 .0 m/s were recorded in the pressure-driven jet during valve closure, and a 1.5 m/s sustained regurgitant jet was observed on the minor orifice side. Additionally, the effects of the impact and subsequent rebound of the occlu der on the flow also were clearly recorded in spatial and temporal detail b y the PIV and LDV measurements, respectively. The PIV results provide a vis ually intuitive way of interpreting the flow while the LDV data explore the temporal variations and trends in detail. This analysis is an integrated f low description of the effects of valve closure and leakage on the pulsatil e regurgitation flow field past a tilting-disc mechanical heart valve (MHV) . It further reinforces the hypothesis that the planar flow visualization t echniques, when integrated with traditional point-to point techniques, prov ide significantly more insight into the complex pulsatile flow past MHVs.