An electromechanical moving-actuator TAH was developed and implanted for 5 days in a calf experiment. The efficiency and durability were further improved using pendulous motion of the actuator. This new pendulum pump has a circular motion produced by gear mechanisms connected to the motor. It has a height (from valves to housing bottom) of 7 cm and centrally directed inlets and outlets for good fittability. Active filling (-10 mmHg) inside inner blood sacs was produced by the suction effects of the outer sacs attached to a moving actuator. Two acute animal experiments were performed using the pendulum pump with a Coridale sheep (50 kg weight), and a male calf (70 kg weight). A test was made of 30 minutes of tether-free operation of the implanted pendulum pump inside the small chest of the calf. The pump shows the engineering feasibility of the implantable electrical TAH inside a human chest cavity.