RESUMO
BACKGROUND: To study the oxygen uptake efficiency and determine usefulness of submaximal parameters of oxygen uptake in systemic lupus erythematosus associated pulmonary arterial hypertension (SLE PAH) on performing a cardiopulmonary exercise test (CPET). METHODS: CPET was performed in 21 SLE PAH patients, equal number of idiopathic pulmonary arterial hypertension (IPAH) patients and controls. Peak VO2, anaerobic threshold (AT), oxygen uptake efficiency slope (OUES) and oxygen uptake efficiency plateau (OUEP) and other CPET parameters were examined. All subjects had pulmonary function test (PFT) at rest, which included FEV1, FVC, FEV1/FVC, DLCO measurements. Right heart catheterization (RHC) was also done in SLE PAH and IPAH patients. CPET parameters were compared with RHC parameters to determine potential correlations. RESULTS: Peak VO2, PETCO2 and peak O2 pulse were lower in SLE PAH than IPAH and controls with OUE being lower during all stages of exercise in SLE PAH. DLCO and FVC values were significantly lower in SLE PAH (p < 0.05). Peak O2 pulse and VO2@AT in SLE PAH and IPAH was low (p < 0.05) and significant difference between SLE PAH and IPAH was seen (p < 0.05). PVR correlated with the lowest VE/VCO2, O2 pulse, peak PETCO2 and OUE in SLE PAH patients (all p < 0.05). CONCLUSIONS: SLE PAH patients have cardiopulmonary exercise limitation with reduced oxygen uptake efficiency. VO2@ at AT, peak O2 pulse and O2 pulse at AT were significantly reduced (p < 0.05). Key CPET parameters correlated with elevated pulmonary vascular resistance (PVR). Submaximal parameters of oxygen uptake are equally useful in SLE PAH.