An implantable system (10) for the cardioversion of the heart of a patient in need of such treatment comprises a plurality of primary electrodes (not shown), a power supply (76, 78), and a control circuit (74). Preferably, at least one auxiliary electrode (not shown) is also included. The plurality of primary electrodes (not shown) are configured for delivering a cardiversion pulse along a predetermined current pathway in a first portion of the heart, the current pathway defining a weak field area in a second portion of the heart.