Serial assessment of peak VO2 and VO2 kinetics early after heart transplantation.
OBJECTIVE
Serial evaluation of aerobic metabolism and exercise tolerance early after heart transplantation (HT).


METHODS
Fifteen heart transplant recipients (HTR), aged 52.0 +/- 9.9 yr (mean +/- SD), not undergoing structured rehabilitation programs, were tested two to four times during the first 2 yr post-HT. As a reference, a group of 11 healthy untrained controls (C) was utilized. Peak heart rate (peak HR), peak O2 uptake (peak VO2), and ventilatory threshold (VT) were determined during incremental bicycle exercise to voluntary exhaustion. VO2 kinetics were evaluated during constant-load exercise below VT, with determination of the duration of the "cardiodynamic" component (TDp) and of the time constant of the "primary" component (taup).


RESULTS
Peak VO2 (L.min-1) was positively related to months post-HT (y=1.17 + 0.02x, P=0.003), and it increased by approximately 30% during the investigated period, although values in HTR were lower than in C (2.19 +/- 0.24). Peak HR was lower in HTR (136 +/- 15 beats.min-1) than in C (168 +/- 5), and it was not related to time post-HT. TDp was longer in HTR (31.4 +/- 6.3 s) than in C (23.2 +/- 6.1), and it was not related to time post-HT. A subgroup of HTR with markedly longer taup during the first months post-HT showed a significant decrease of this parameter as a function of time post-HT.


CONCLUSIONS
Aerobic metabolism is impaired in HTR. Both central (cardiovascular) and peripheral (skeletal muscle) factors contribute to the reduced exercise tolerance. HTR showed, during the first 2 yr post-HT, a significant increase in peak VO2 and (in the patients with the slowest VO2 kinetics during the first months after HT) a significant improvement of the VO2 kinetics. The main gains seem to occur at the peripheral level.
Department of Surgery and Bioengineering, Policlinico, University of Siena, Siena, Italy.
Emma
E
Borrelli
Silvia
S
Pogliaghi
Alessandro
A
Molinello
Francesco
F
Diciolla
Massimo
M
Maccherini
Bruno
B
Grassi
D015444:Exercise; D005080:Exercise Test; D017079:Exercise Tolerance / Q000502:physiology; D006339:Heart Rate; D016027:Heart Transplantation / Q000534:rehabilitation; D006801:Humans; D008297:Male; D008875:Middle Aged; D011659:Pulmonary Gas Exchange / Q000502:physiology*; D013997:Time Factors