Abstract: A multiple monopolar system and method for measuring stroke volume of a patient's heart. An intracardiac impedance catheter is provided with a plurality of monopolar electrodes axially spaced along the surface of its distal end, and is used in conjunction with a distant reference electrode which may, for example, be incorporated into the conductive case of a pacemaker. The proximal end of the catheter is attached to the pacemaker, which, in addition to pulse generator circuitry and circuitry for sensing electrical activity of the heart and for controlling pacing rate, includes a constant-current source for current injection into the volume of blood in the patient's ventricle and an impedance processor for measuring the resultant voltage between one of the monopolar electrodes in the ventricle and the pacemaker case and for calculating stroke volume therefrom.

Abstract: A method and apparatus is provided for enhancing blood circulation, and thereby reducing fatigue, in a skeletal muscle used for powering a cardiac assist device wherein the muscle is positioned to compress a blood reservoir in response to muscle contracting stimuli. Enhanced perfusion of the skeletal muscle is achieved by delaying blood flow into the reservoir for a period of time following each muscle contraction.