Refractory period stimulation (RPS) disclosed herein includes apparatus and methods to enhance cardiac performance by delivering monophasic stimulation pulses during the refractory period. The disclosure describes several system level improvements to RPS that include one or more of the following: (i) Delivery of RPS therapy pulses at multiple sites in an automatically alternating way to avoid increasing demand at any one location for prolonged periods of time. (ii) Delivery of RPS therapy pulses at multiple sites to determine one or more optimal electrode configurations for chronic RPS therapy delivery. (iii) Use of separate electrode(s) for sensing ventricular activity to properly time and adjust the application of RPS thereby avoiding limitations associated with electrode polarization that occurs due to the amount of energy delivered during the RPS. (iv) Use of a relatively long active recharge pulse at the RPS stimulation electrodes to remove the undesirable effects of polarization.
