Simple electrical model of the circulation to explore design parameters for a skeletal muscle ventricle

To efficiently investigate a variety of designs for an accessory skeletal muscle ventricle for circulatory assistance, we developed an electrical model of the human circulatory system. Heart and blood vessels were modeled as resistive-capacitive networks, pressures as voltages, blood flow as electric current, and the cardiac valves as diodes. Pumping of blood was simulated by the application of damped rectangular voltage pulses to the capacitances of the cardiac ventricles and the skeletal muscle ventricle. Three configurations of a skeletal muscle ventricle were studied: the apico-aortic, in which the skeletal muscle ventricle is interposed between the left ventricle and the abdominal aorta; the aorto-aortic, in which the skeletal muscle ventricle is interposed between the thoracic aorta and the abdominal aorta; and the atrial-aortic, in which the skeletal muscle ventricle is interposed between the left atrium and abdominal aorta. The three skeletal muscle ventricle designs were tested as counterpulsatile assist devices in simulations of the normal circulation and congestive heart failure. Performance of the various skeletal muscle ventricle designs was evaluated by comparing total output, mean left ventricular power expenditure, mean skeletal muscle ventricle power expenditure, and mean perfusion pressure of the skeletal muscle comprising the pouch. Under both normal heart and heart failure conditions, the apico-aortic design was superior to the aorto-aortic and to the atrial-aortic designs. With optimal stimulation parameters, the apico-aortic design reduced left ventricular minute work to 16% of normal during simulated heart failure while maintaining a viable resting cardiac output of 3.4 L/min. Such electronic models of the circulation allow easy investigation of various structural designs and activation protocols for a skeletal muscle ventricle.