Influence of the exercise protocol on peak VO2 in patients after heart transplantation.

BACKGROUND

The protocol and the duration of an exercise test have considerable influence on peak oxygen consumption (VO2). 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 VO2 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 VO2 (20.9 +/- 5.2 vs 20.5 +/- 5.9 ml/kg/min; p = 0.538).

CONCLUSIONS

Peak VO2 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 VO2.