A skeletal muscle actuator for an artificial heart

The authors developed a system to use skeletal muscle as an artificial heart actuator. This system consists of a flexible rod, sheath, crank, and cam to transmit the muscle power to a pusher plate pump and actuate it. The latissimus dorsi muscle was dissected at the lower ribs, and its end was connected with the flexible rod. The contraction of skeletal muscle was linearly transmitted, with the rod introduced inside the sheath, to the pump. The whole system was implanted in dogs (14-18 kg) and pump performance was evaluated with a mock circulatory system (preload = 10 mmHg, afterload = 75 mmHg). In these experiments, the pump output was maintained at 0.8 to 2.0 L/min (60 bpm) for 200 min, with a non-preconditioned muscle that was stimulated continuously. The output obtained was 2.5 mW/gram. Efficiency of this system was about 50% of the muscle power available. When the muscle was stimulated intermittently every 30 min, pump flow was maintained at > 0.8 L/min for 20 hr. Advantages of this system are: 1) the muscle power was linearly transmitted effectively, 2) this system could be installed with minimal surgery and without interruption in blood flow to the muscle, 3) the muscle is free from high intraventricular pressure that caused ischemia and, 4) the muscle can be set to the proper length in diastole to potentiate strong contractions.