Dependencies of ventricular and arterial pressures on the dynamical properties of afterload and viscous resistance of ventricular muscle have been analyzed by a theoretical model. The ventricular contractile element was expressed by a time varying capacitor and arterial system was described by 2 compartments, each of which was composed of resistances and capacitors. With time dependent decreases in arterial resistance and time dependent increase in ventricular viscous resistance, pressures in ventricle and artery have been reduced. With reduction of aortic compliance, those pressures have been elevated while peripheral compliance did not contribute to them. Time dependent decrease in aortic valvular resistance reduced ventricular pressure while it elevated arterial pressure.