Electrode systems have been developed for use in perfusion systems to measure the electrical activity of an explanted heart and to provide defibrillation energy as necessary. The perfusion systems maintain the heart in a beating state at, or near, normal physiological conditions; circulating oxygenated, nutrient enriched perfusion fluid to the heart at or near physiological temperature, pressure and flow rate. These systems include a pair of electrodes that are placed epicardially on the right atrium and left ventricle of the explanted heart, as well as an electrode placed in the aortic blood path.