Cardiopulmonary Test in Fontan Patients: Is the Type of Ergometer Critical?

Cardiopulmonary exercise testing (CPET) is recommended as part of routine care in people with congenital heart disease. A significant difference has been observed in many CPET parameters, depending on the ergometer and exercise protocol used. The aim of this study is to investigate such differences in Fontan patients. All Fontan patients (<40 years old, NYHA class I/I-II) underwent two consecutive CPETs on different ergometers (treadmill with ramped Bruce protocol versus cycle ergometer with ramp protocol) within less than 12 months. The exclusion criterion was the presence of significant clinical/anthropometric changes between the two tests. Anthropometric, surgical, clinical, electrocardiogram (ECG) and CPET data were collected. 47 subjects were enrolled (25 males, mean age 16.4 at first test). Peak heart rate (HR) tended to be higher on the treadmill (p = 0.05 as % of predicted, p = 0.062 in absolute value). Peak oxygen consumption (VO₂) (mL/min, mL/kg/min, and % of predicted) was significantly higher on the treadmill (p < 0.01), as well the VO₂ at the ventilatory anaerobic threshold (VAT) and the peak oxygen pulse. A different kinetics of the oxygen pulse wave was observed in the same patient comparing the two testing modalities. Maximal respiratory-exchange-ratio values (>1.1) were reached more frequently on the cycle ergometer (p < 0.001). The minute ventilation-carbon dioxide output slope (VE/VCO₂ slope) was not different between the two tests (p = 0.400). Many parameters of CPET may differ depending on the ergometer used. These should be considered in clinical evaluation of Fontan patients and when exercise is to be prescribed.