A magnetically suspended and hydrostatically stabilized centrifugal blood pump.

A magnetically suspended centrifugal blood pump intended for application as a long-term implantable ventricular assist device has been built and tested. The rotor is freely suspended in the blood by magnetic and hydrostatic restoring forces. This design obviates the need for bearings and shaft seals, and eliminates the problems of reliability and thrombogenicity associated with them. The positional stability and hydrodynamic performance of the pump has been characterized in vitro at flows of up to 10 L/min at physiologic pressures. Radial position control is realized by an analog electronic feedback control system. The pressure distribution in the fluid surrounding the rotor provides dynamic control in the axial direction with no active feedback. Rotor excursion is less than 50 microns (mu) when the housing receives an impulse peaking at an acceleration of 40 g or upon sudden blockage of the flow. In vitro blood measurements indicate an acceptable level of hemolysis compared with that of a standard centrifugal pump.