the rotor and the housing the differences in centrifugal pump disk support structure design lie in the location and shape of the support the tradeoff between hemolysis and thrombosis is important disk supports that are too close to the center of the rotor could produce eddies where stagnation could occur causing thrombi formation alternatively a set of disk supports on the outermost edge may create an unacceptably high level of trauma to blood cells due to the increased velocity present at the outer radii of the disks a teardrop shaped disk support structure that is narrow near the center and widens as it moves radially outward acts as an effective shape that eliminates areas of stagnation while allowing smooth movement around it limiting both hemolysis and thrombosis an important design criterion for a pediatric ventricular assist device u201c vad u201d is the priming volume of the device which cannot use a significant percentage of the infant 39 s overall blood volume simply to fill up the pump in a preferred embodiment this pump minimizes priming volumes in two ways first the inter disc spacing is reduced to just above the point where hemolysis begins to increase u02dc 1 mm a function of blood viscosity and surface roughness of the rotor in a preferred embodiment the overall rotor is elevated off the bottom of the housing in order to prevent excessive hemolysis in another preferred embodiment the fluid encounters disks of successively increasing diameter as it flows from inlet to outlet as shown in fig7 the foregoing disclosure and description of the inventions are illustrative and explanatory various changes in the size shape and materials as well as in the details of the.