FIGURE 1.

a) Demographics, pulmonary function, resting haemodynamics and cardiopulmonary exercise testing parameters for patients with mitochondrial myopathy (MM) and pulmonary arterial hypertension (PAH). Data are presented as mean±sem unless otherwise stated. Independent samples Student's t-test was used to compare parametric data between groups. b–e) Key cardiovascular responses during noninvasive cardiopulmonary exercise testing in two representative patients with PAH and a patient with MM. An age- and sex-matched healthy control was also added for comparison. This representation should be considered simply as a reference of expected values and kinetics for the variables of interest: how subjects would have performed had they not been ill. Note that while O₂ pulse was downwardly displaced in the MM patient without a discernible change in curve appearance, PAH patients showed a flattened (PAH 1) or decreasing (PAH 2) trajectories at the late stages of exercise (c and e). Those abnormalities coincided with upward inflections of heart rate (HR) as a function of O₂ uptake (V′_O2) (arrows) in patients with PAH (b), which is not seen in the representative MM patient (d). BMI: body mass index; FEV₁: forced expiratory volume in 1 s; FVC: forced vital capacity; TLC: total lung capacity; D_LCO: diffusing capacity of the lung for carbon monoxide; P_aO2: arterial oxygen tension; P_aCO2: arterial carbon dioxide tension; mPAP: mean pulmonary arterial pressure; PVR: pulmonary vascular resistance; V′_O2: oxygen uptake; AT: anaerobic threshold; WR: work rate; V′_E: minute ventilation; V′_CO2: carbon dioxide output; P_ETCO2: end-tidal carbon dioxide tension; S_pO2: oxygen saturation measured by pulse oximetry; unl: unloaded exercise; rec: recovery. *: p<0.05.