Background: The aim of this study was to compare peak oxygen consumption (VO2), heart
rate (HR) reserve and HR recovery in early and late heart transplant recipients. Moreover, we
also aimed to correlate peak VO2 and HR reserve.

Methods: Fivteen heart transplant recipients (8 early and 7 late), 8 ± 3 and 161 ± 58 months
after transplantation, respectively, performed a cardiopulmonary exercise test.

Results: Early heart transplant recipients showed lower HR reserve compared to late heart transplant
recipients, 39 ± 15 vs. 58 ± 19 bpm (p = 0.049), respectively. Peak VO2 (23.4 ± 4 vs. 21.8 ± 5 mL/kg/min, p = 0.56), VO2 respiratory compensation point (18.7 ± 2 vs. 18.5 ± 4 mL/
/kg/min, p = 0.48) and time of exercise testing (14 ± 3 vs. 13 ± 3 min, p = 0.95) %age-
-predicted peakVO2 (65 ± 12 vs. 70 ± 10%, p = 0.24) were not different between the groups.
Moreover, peak VO2 and %age-predicted peakVO2 correlated with HR reserve only in early heart
transplant recipients (r = 0.89, p = 0.003 and r = 0.71, p = 0.04, respectively). Early heart
transplant recipients increased HR (2.5 ± 2.0% at fi rst minute and 0.7 ± 2.3% at the second
minute), while late recipients decreased HR (–6.0 ± 4.7 at fi rst minute and –15.5 ± 2.4 at the
second minute) at the recovery period of cardiopulmonary exercise test.

Conclusions: Exercise capacity did not show difference between early and late heart transplant
recipients. HR reserve was higher in late compared to early recipients. HR reserve only
correlated with peak VO2 in early recipients. Moreover, only late heart transplant recipients
showed decrease in HR during the recovery period of cardiopulmonary exercise test.