A new type of electromechanical total artificial heart based on a moving-actuator mechanism was developed to decrease the total pump size and to improve the fitting characteristic of the pump to atrial remnants and arterial vessels. The blood pump consists of three major parts: right and left blood sacs and a moving pump actuator between two sacs. The total weight is 810 g and the volume of the pump is 770 ml. The actuator rolls back and forth on a circular track, producing alternating blood ejection. The pump performance was evaluated in mock circulation and animal implant experiments. The pump was implanted for 100 h in a calf (approximately 100 kg) with a stable hemodynamic state until accidental (electrical short circuit) death.