Work-rate affects cardiopulmonary exercise test results in heart failure

Aims: Cardiopulmonary exercise test (CPET) is used to evaluate patients with chronic heart failure (HF) usually by means of a personalized ramp exercise protocol. Our aim was to evaluate if exercise duration or ramp rate influences the results. Methods and results: Ninety HF patients were studied (peak V̇O2: >20 ml/min/kg, n=28, 15-20 ml/min/kg, n=39 and <15 ml/min/kg, n=23). Each patient did four CPET studies. The initial study was used to separate the subjects into three groups, according to their exercise capacity. In the remaining studies, work-rate was increased at three different rates designed to have the subjects reach peak exercise in 5, 10 and 15 min from the start of the ramp increase in work-rate, respectively. The order was randomized. The work-rate applied for the total population averaged 22.7±8.0, 11.6±3.7, 7.5±2.9 W/min with effective loaded exercise duration of 5 min and 16 s±29 s, 9 min and 43 s±49 s and 14 min and 32 s±1 min and 12 s for the 5-, 10- and 15-min tests, respectively. Peak V̇O2 averaged 16.9±4.3*, 18.0±4.4 and 18.0±5.4 ml/min/kg for the 5-, 10- and 15-min tests, (*=p<0.001 vs. 10 min). The shortest test had the lowest peak heart rate and ventilation and highest peak work-rate. Peak V̇O2 and heart rate were lowest in 5-min tests regardless of HF severity. The ΔV̇O2/Δwork-rate was lowest in 5-min tests and highest in 15-min tests. At all ramp rates, ΔV̇O2/ Δwork-rate was lower for the subjects with the lower peak V̇O2. The V̇e/V̇CO2 slope and V̇O2 at anaerobic threshold were not affected by the protocol for any grade of HF. Conclusions: In chronic HF, exercise protocol has a small effect on peak V̇O2 and ΔV̇O2/Δwork but does not affect V̇O2 at anaerobic threshold and V̇e/V̇CO2 slope.