A system for improving heart muscle response during a pre-ejection phase in the heart muscle pumping cycle requires a catheter having a pressure transducer and a fluid device mounted at its distal end. Also included is a pump connected to the proximal end of the catheter in fluid communication with the fluid device. A computer will activate the pump in response to a predetermined signal from the pressure transducer to inject and maintain an increased fluid volume in the pumping chamber of the heart for a predetermined time interval Δt during the pre-ejection phase. This supplements the isometric pressure in the heart's pumping chamber in preparation for a subsequent ejection of blood from the pumping chamber.
