Abstract: A process and apparatus for providing an electrophysiologic indicator of reversible myocardial ischemic injury as well as a procedure and apparatus for providing a method of assessing the status of myocardial preservation during elective cardioplegic arrest in order to assure complete electromechanical arrest from the onset of the application of the standard cardioplegic techniques. The procedure for establishing an indication of reversible myocardial ischemic injury involves implanting multiple electrodes in the myocardial tissue and sensing the instantaneous unipolar electrical potentials of the electrodes and comparing those sensed potentials with a series of registered potentials for healthy tissue.