Abstract: A blood sac for a heart assist device having pump pusher plates attached to its sides and an actuator system that is pivotally attached to the plates. The actuator mechanism has a movable fulcrum and levers. The movable fulcrum allows the levers of the actuator mechanism to move the pump pusher plates in a straight line toward and away from each other. The actuator mechanism allows the heart assist device to pump blood through any valve or parts of the heart to which it may be attached. The actuator mechanism allows full stroke variable speed to be imparted to the pump pusher plates. The actuator mechanism allows continuous active filling of the blood sac. The actuator mechanism is powered by a toroidally wound brushless DC motor, the speed of which is controlled by a microprocessor based upon information supplied to the microprocessor from a sensor.