Abstract: An electromagnetic drive for use in a ventricular assist device. The electromagnetic drive provides adjustment to the device pressure according to the current through an electromagnet. The device includes a pair of U-shaped cores, each having a center section and two legs; one or more coils, each wound around a selected U-shaped core that, when electrically energized, generate a magnetic flux and define one or more pairs of magnetic poles each having a polar axis; and an armature between the U-shaped cores having two non-magnetic ends and a permanent magnet therebetween for generating a magnet force on the armature resulting from the attraction of the magnet to the U-shaped cores when the coils are not electrically energized. The drive geometry reduces lateral instability and device size and increases magnetic efficiency and linearity. Preferably, a coil is wound around each center section. Alternatively, the coils are wound around the legs.

Abstract: A ventricular assist device (VAD) for assisting either or both heart ventricles. The VAD pumps blood between an inlet and an outlet. The VAD includes a bearingless electromagnetic drive unit comprising an armature disposed between two cores, a compressible sac, valves, and a frame. The armature moves toward the sac in an eject stroke for expelling blood therefrom to the outlet. An energy storage element is preferably included and adapted to store and release energy from the drive unit. The armature is decoupled from the compressible chamber after completion of the eject stroke such that the armature retracts. Following retraction, the sac is passively filled with blood from the inlet and the energy stored in the storage element during retraction is delivered during the eject stroke. The device preferably has two cores with coils wound around each core's center section or legs. Alternatively, one of the cores is coil-less.