Flow behavior within the 12-cc Penn State pulsatile pediatric ventricular assist device: an experimental study of the initial design.

Planar particle image velocimetry was used to explore the flow behavior of the newly designed 12-cc Penn State pneumatic pediatric assist pump. Wall shear maps complemented the velocity data. Bjork-Shiley Monostrut 17-mm mechanical heart valves were used in the inlet and outlet ports. In comparison with larger Penn State pumps, the 12-cc device is not only smaller but has reduced valve effective orifice areas and more highly angled valve ports. In contrast to results from the larger pumps, the flow field was highly three dimensional during early diastole with poorer penetration by the valve inlet jet. This led to a later start to a "wall washing" rotational pattern. A significant separation region, never before observed, was created upstream of the outlet valve leaflet during late diastole--effectively reducing the area and increasing the pressure drop through the valve. Wall shear maps suggest that regions of low shear might persist throughout the cycle at the bottom of the pump on the outlet side. An attempt to improve the flow field characteristics by exploring different valves, valve orientations and inlet valve angles, systolic/diastolic flow timing, and perhaps a larger outlet valve was planned.