To test the hypothesis that exercise response changes with time after cardiac transplantation, we investigated the cardiorespiratory responses of nine orthotopic heart transplant patients (52.4 ± 2 yr) during graded exercise tests (30 W·3 min-1) done at 1, 3, 6, 9, and 12 months post-surgery. At peak exercise, 1) oxygen uptake per kg of body weight(˙VO2), minute ventilation (˙VE) and oxygen pulse (O2 pulse) did not change significantly between 1 and 12 months post-surgery; 2) transplanted heart rate (HRt) and delta heart rate (peak exercise heart rate - resting heart rate) increased significantly over time (P < 0.01; P < 0.05) with a marked increase between 1 and 3 months(P < 0.05); and (3) a significant negative correlation existed between O2 pulse and HRt (r = -0.36, P < 0.05), whereas no correlation was found between delta heart rate and delta˙VO2 (peak exercise ˙VO2 - resting ˙VO2, 1·min-1). During submaximal exercise, HRt increased significantly over time (P < 0.001); ˙VO2, ˙VE, and O2 pulse showed no significant change; and the˙VO2-HRt relationship shifted toward higher values of HRt. We conclude that, in the absence of formal physical training, the exercise response of denervated transplanted heart increases in relation to post-surgery time but does not affect oxygen uptake at submaximal and peak levels of exercise.
Service d'Exploration de la Fonction Respiratoire; Service de Chirurgie Cardiovasculaire et Thoracique, Hôpital Arnaud de Villeneuve, 34295 Montpellier Cedex 5, FRANCE; and Laboratoire Sport, Santé et Développement, University of Montpellier I, 34090 Montpellier, FRANCE
Submitted for publication September 1994.
Accepted for publication April 1995.
This work was supported by an “Institut National de la Santé et de la Recherche Médicale” grant CRE 93 1102.
Address for correspondence: Jacques Mercier, M.D., Ph.D., Service d'Exploration de la Fonction Respiratoire, Hôpital Arnaud de Villeneuve, 34295 Montpellier Cedex 5, France.