Cardiac function after orthotopic heart transplantation: Response to postural changes, exercise, and beta-adrenergic blockade
To prospectively assess the response of orthotopic heart transplant recipients to exercise before and after beta-adrenergic blockade, we investigated 35 orthotopic heart recipients, all with clinically stable conditions and without rejection, and five control, healthy subjects. Radionuclide angiography was performed at rest and during supine bicycle exercise, before and after beta-blockade. At rest, heart rate, systolic and diastolic pressures, and end-systolic volume were higher, whereas the end-diastolic volume and stroke volume indexes, cardiac index, and ejection fraction were significantly lower in the transplant recipients than in healthy control subjects. During exercise, before beta-blockade, transplant recipients attained a lower maximal heart rate and smaller increments in heart rate than did the control subjects. The cardiac index increased during exercise because of an increase in stroke volume (43%) and heart rate (32%) in the transplant recipients and nearly exclusively (93%) because of an increase in heart rate in the normal subjects. After beta-blockade, the ejection fraction, the stroke volume, and the cardiac index fell significantly at rest in both groups. The fall in ejection fraction was greater in the transplant recipients than in the control subjects (-16% +/- 12.6% versus -5.4% +/- 2.6%, respectively; p = 0.0002). After beta-blockade, lower maximal heart rate, ejection fraction, and cardiac index were achieved during exercise in both groups. The peak exercise cardiac index was 42% lower in transplant recipients than in control subjects after beta-blockade. Thus, cardiac performance during exercise is impaired in orthotopic heart transplant recipients. Acute beta-adrenergic blockade accentuates the impairment in ventricular performance and appears to be detrimental in these patients.