1. A multi-electrode implantable cardiac device for monitoring ischemia, comprising: a plurality of electrodes configured to be used for sensing; a pulse generator in electrical communication with the plurality of electrodes; and a controller configured to automatically select a plurality of candidates for monitoring ischemia, each of the candidates consisting of a combination of the plurality of electrodes, to receive a shift in a ST segment of one of an electrocardiogram and a cardiac electrogram detected using each of the candidates, to automatically identify one of the candidates for optimally monitoring ischemia based on a comparison of one of the detected ST segment shifts to another detected ST segment shift, and to automatically apply the identified candidate to monitor ischemic activity.