Abstract: An auxiliary artificial heart which comprises a pump having a single opening that is connected to the aorta and is operable in synchronism with the heart of the patient to assist the normal function of the heart. The auxiliary artificial heart comprises a housing having the single opening therein and a diaphragm which is movable toward and away from the opening by a rotating reversible electric stepping motor. Rotation of the motor rotates circumferentially spaced roller pins which extend radially inwardly into engagement with a helical groove of a screw attached to the diaphragm such to translate the screw and move the diaphragm toward and away from the opening. The housing is sealed to enclose a gas in the housing such that the differential pressure caused by movement of the screw assists the diaphragm in its movement.