An apparatus for treating an infection which may occur in the biofilm which surrounds an implanted cardiac stimulation device, e.g., a cardioverter-defibrillator (ICD) or pacemaker. Such infections are relatively untreatable by conventional antibiotics treatments. Thus, explanting of the implanted devices may be required. Accordingly, the present apparatus provides an electrical treatment that enables a biocide, i.e., an antibiotic, to successfully treat the infection within the biofilm and thus avoid the necessity to explant the device. Furthermore, the present invention provides this electrical treatment in a manner to not interfere with the stimulation pulses of the cardiac stimulation device by alternatively delivering current pulses during atrial and ventricular refractory periods or a high frequency square wave at a frequency that exceeds the frequency response of the heart muscle.