Patients 18 years and above who are on a wait list for heart transplant at a UNOS-approved heart transplant center, whose institutional review board has approved this protocol, may be eligible for this study. Healthy volunteers will also be included in the study to establish a database of normal values for comparison with patients undergoing heart transplant. In addition, patients who have had a heart transplant within the past 1 to 5 years will be enrolled in a pilot study. Normal volunteers will be screened for participation with an electrocardiogram (EKG) and echocardiogram, non-invasive tests to evaluate heart function.