CARDIAC-FUNCTION AFTER ORTHOTOPIC HEART-TRANSPLANTATION - RESPONSE TOPOSTURAL CHANGES, EXERCISE, AND BETA-ADRENERGIC-BLOCKADE

To prospectively assess the response of orthotopic heart transplant re cipients to exercise before and after beta-adrenergic blockade, we inv estigated 35 orthotopic heart recipients, all with clinically stable c onditions and without rejection, and five control, healthy subjects. R adionuclide angiography was performed at rest and during supine bicycl e exercise, before and after beta-blockade. At rest, heart rate, systo lic and diastolic pressures, and end-systolic volume were higher, wher eas the end-diastolic volume and stroke volume indexes, cardiac index, and ejection fraction were significantly lower in the transplant reci pients than in healthy control subjects. During exercise, before beta- blockade, transplant recipients attained a lower maximal heart rate an d smaller increments in heart rate than did the control subjects. The cardiac index increased during exercise because of an increase in stro ke volume (43%) and heart rate (32%) in the transplant recipients and nearly exclusively (93%) because of an increase in heart rate in the n ormal subjects. After beta-blockade, the ejection fraction, the stroke volume, and the cardiac index fell significantly at rest in both grou ps. The fall in ejection fraction was greater in the transplant recipi ents 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 exerc ise in both groups. The peak exercise cardiac index was 42% lower in t ransplant recipients than in control subjects after beta-blockade. Thu s, 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 i n these patients.