A parametric study of valve orientation on the flow patterns of the Penn State pulsatile pediatric ventricular assist device

Abstract

Because of the shortage of organs for transplant in pediatric patients with end-stage heart failure, Penn State is developing a pneumatically driven 12 cc pulsatile pediatric ventricular assist device (PVAD). A major concern is the flow field changes related to the volume decrease and its effect on device thrombogenicity. Previous studies of similar devices have shown that changes in the orientation of the inlet valve can lead to improvement in the flow field. Herein, the fluid dynamic effects of orientation changes at both the inlet and outlet valves are studied. Using two-dimensional particle image velocimetry, we examine the flow field in vitro using an acrylic model of the PVAD in a mock circulatory loop. Regardless of valve orientation, the overall flow pattern inside the PVAD remains similar, but important differences were seen locally in the wall shear rates, which is notable because shear rates >500 s may prevent thrombus formation. As the inlet valve was rotated toward the fluid side of the PVAD, we observed an increase in inlet jet velocity and wall shear rates along the inlet port wall. A corresponding rotation of the outlet valve increases the wall shear rate along the outer wall near the device outlet. Wall shear rates were all higher when both valves were rotated toward the fluid side of the device, with the best rates found at orientations of +15 degrees for both the inlet and outlet valves. Overall, orientations of +15 degrees or +30 degrees of both the inlet and outlet valve resulted in an increase in wall shear rates and could aid in the reduction of thrombus formation inside the PVAD.