A pulse generator housing for enclosing and containing pulse generator defibrillation circuitry. At least one surface is electrically conductive and connected to the pulse generator circuitry for delivering defibrillating energy to the heart. The pulse generator housing is implanted in the pectoral region proximate the heart with the conductive surface facing the heart. Other implantable electrodes are discharged against the pulse generator housing electrode. Specifically, particular ones of the implantable electrodes are selected for discharge against the pulse generator housing according to detected heart conditions.