In general, the disclosure describes implantable pulse generators (IPGs) adapted to deliver stimulation to refractory myocardial tissue. An IPG nominally delivers one to six monophasic stimulation pulses. Because monophasic stimulation tends to accumulate polarization, a programmable blanking period of between about 20 milliseconds (ms) and about 300 ms is implemented (subsequent to delivery of the last pulse in a RPS pulse train) to allow recovery from polarization. The stimulation pulse width is about 0.03 ms to about 1.6 ms and voltage amplitude of 0.5 volts to 8 volts at about 50 Hz. The amplitude of electrical current of the stimulation pulses is less than or equal to approximately 50 milliamps. The pulses are delivered to multiple sites within a cardiac chamber and device performance and/or diagnostic information can be stored within a memory structure and reviewed to confirm delivery of a desired therapy regimen.