Determining cardiac electrical activity from the body surface potentials is known as the inverse problem in electrocardiography. Epicardial potentials have been shown to reflect accurately the underlying electrical activity. A non-invasive method of recovering epicardial potentials from body surface potentials would permit the detection and localization of abnormal electrical activity prior to surgery, may shorten the time necessary to map the heart potentials intraoperatively, and may eliminate the need for detailed invasive surgical mapping.