A consequence of orthotopic heart transplantation is permanent denervation of the donor heart. The specific aim of the proposed study, "The Effect of Orthostatic Change on Cardiovascular Stability in Orthotopic Heart Transplant Recipients" is to compare changes in cardiac output (CO), stroke volume (SV), mean arterial pressure (MAP), heart rate (HR), systemic vascular resistance (SVR), and norepinephrine (NE) levels in heart transplant recipients and in normal subjects when both are subjected to a tilt table test. The long-term objectives include determining how physiologic responses are altered when autonomic function is disrupted by cardiac denervation. Using a two-group, quasi-experimental pretest- posttest design, heart transplant recipients and age- and sex-matched normal controls will be subjected to passive tilt from horizontal to 70 degrees via a motorized tilt table. Exclusion criteria for transplant subjects include: evidence of cardiac or renal failure, fluid retention, dizziness, syncope, or orthostatic hypotension. Exclusion criteria for control subjects include: orthostatic hypotension, syncope, palpitations or any other manifestation of cardiac or endocrine dysfunction. Repeated measures of CO, SV, MAP, HR, SVR, and NE levels will be taken before, during, and after passive tilt. Data will be analyzed using repeated measures multivariate analysis of variance. Understanding how physiologic responses are altered when autonomic function is disrupted will enhance nurses' abilities to provide effective care and to promote independent activity among heart transplant recipients.