A device and method for delivering high-energy electrical stimulation to the heart in order to improve cardiac function in heart failure patients. The high-energy stimulation mimics the effects of exercise and improves symptoms even in patients who are exercise intolerant. The high-energy stimulation may be delivered on an intermittent basis either as pacing pulses in accordance with a programmed pacing mode and with a higher pacing pulse energy than used for conventional pacing or as low energy shock pulses.