Exercise energy expenditure in patients with idiopathic pulmonary arterial hypertension: impact on clinical severity and survival

Patient with idiopathic pulmonary hypertension (IPAH) develop peripheral inefficiency which could lead to an increase total energy expenditure and that could have a significant prognostic impact. To test the hypothesis, fifty-five consecutive stable IPAH patients (mean age 51 ± 17 years) and 24 matched controls underwent an incremental exercise test and followed for a 5 years’ period. Total energy expenditure was assessed as the ratio between total VO2 uptake (during both effort and recovery) and total external work (VO2 TOT/WTOT ). Patients with IPAH had a lower exercise capacity and a significantly higher VO2 TOT/WTOT than controls (VO2 TOT/WTOT 0.33 ± 0.09 ml/j vs 0.22 ± 0.04 ml/j, p < 0.0001). Among patients, VO2 TOT/WTOT was higher in whom died during follow up compared to survivors (0.41 ± 0.11 ml/j vs 0.30 ± 0.06 ml/j, p < 0.0001). In multivariate Cox regression analysis VO2 TOT/WTOT , gender, PETCO2 peak, V˙ O2 peak were independent risk factors for death. Patients with IPAH have shown a less efficient muscular oxygen utilization than controls. Notably the high energy expenditure has a relevant independent prognostic impact.