Influence of the exercise protocol on peak V02 in patients after heart transplantation

Background: The protocol and the duration of an exercise test have considerable influence on peak oxygen consumption (Vo(2)). On a bicycle ergometer, the use of a ramp protocol with a target exercise duration of 8 to 12 minutes is recommended to reliably measure maximal oxygen uptake. Because of cardiac denervation, heart transplant recipients have a delayed heart rate adaptation to exercise, and oxygen uptake kinetics are altered. Methods: We investigated whether the rate of workload increase during exercise testing would influence peak Vo(2) after heart transplantation. Two symptom-limited exercise tests, applying a ramp and a 3-minute step protocol were effectuated on a bicycle ergometer. Results: Seventeen patients (14 men, 3 women), mean age 58.4 +/- 12.7 years, at 64.5 +/- 26.7 months post-transplant participated in the study. No statistically significant differences between the 2 protocols were found regarding total exercise duration until exhaustion (8:42 +/- 2:09 vs 8:48 +/- 2:27 minutes, p = 0.705), maximal workload reached (117.9 +/- 42.6 vs 106.4 +/- 40.5 W; p = 0.055), peak heart rate (135.8 +/- 11.6 vs 131.2 +/- 14.8 beats/min.; p = 0.061), and peak Vo(2) (20.9 +/- 5.2 vs 20.5 +/- 5.9 ml/kg/min; p = 0.538). Conclusions: Peak Vo(2) seems insensitive to a stepwise or ramping exercise protocol in heart transplant patients when the workload increments are chosen in a way that a total exercise time of 8 to 12 minutes is achieved. Both protocols can therefore be applied to evaluate peak Vo(2).