Background: Exercise capacity, assessed by cardiopulmonary exercise treadmill testing (CPET), does not return to normal following heart transplantation. This study evaluated the ventilatory response to exercise and the kinetics of oxygen (O(2)) recovery in heart transplant recipients (HTR) compared to healthy volunteers (HV) and heart failure patients.
Methods: Eighteen patients with end-stage heart failure (ESHF), 12 with mild heart failure (MHF) matched for peak oxygen consumption (Vo(2)) with the HTR, 12 HTR and 12 HV underwent CPET for measurements of peak Vo(2), Vo(2) at anaerobic threshold (AT), first-degree slope of Vo(2) decline during early recovery (Vo(2)/t-slope), time required for a 50% fall from peak Vo(2) (T(1/2) of Vo(2)) and the slopes of VE/Vco(2) and VE/Vo(2).
Results: The MHF and HTR groups had similar ventilatory responses to exercise and O(2) recovery kinetics. Peak Vo(2) (18.5 +/- 5.7 vs 9.4 +/- 0.9 ml/kg/min, p < 0.001), AT (13.8 +/- 4.8 vs 6.7 +/- 1.8 ml/kg/min, p < 0.001) and Vo(2)/t-slope (0.6 +/- 0.2 vs 0.3 +/- 0.2 liter/min/min, p = 0.055) were higher in the HTR than in the ESHF group. In contrast, HTR had lower VE/Vco(2)-slope (31.4 +/- 3.8 vs 39.2 +/- 9.9, p = 0.015) and T(1/2) Vo(2) (1.5 +/- 0.3 vs 2.4 +/- 1.1 minute, p = 0.014) than the ESHF group. Compared to HV, HTR had lower Vo(2) peak (18.5 +/- 5.7 vs 28.4 +/- 6.9 ml/kg/min, p < 0.001), AT (13.8 +/- 4.8 vs 19.8 +/- 4.5 ml/kg/min, p = 0.04), Vo(2)/t-slope (0.6 +/- 0.2 vs 1.0 +/- 0.4 liter/min/min, p = 0.005) and steeper VE/Vco(2) slope (31.4 +/- 3.8 vs 23.6 +/- 2.7, p = 0.062). Heart rate deceleration during recovery was significantly slower in HTR than in all other groups.
Conclusions: Exercise intolerance and delayed O(2) recovery kinetics were only partially reversed after heart transplantation. This finding suggests that some of the pathophysiologic mechanisms of heart failure persist after heart transplantation.