This research study is designed to measure non-invasive ways to assess rejection along with the standard planned endomyocardial biopsies you will have after heart transplantation. First, the investigators plan to test the effectiveness of the investigational use of the CMI 2406 Magnetocardiograph that has been approved by the U.S Food and Drug Administration (FDA). While the device used in the study is FDA-approved for the non-invasive measurements and recordings of the heart's magnetic field reflecting the heart's electrical currents, it is not yet approved for the specific use of detection of transplant rejection.