Clinical utility of ventilatory and gas exchange evaluation during low-intensity exercise for risk stratification and prognostication in pulmonary arterial hypertension.

BACKGROUND AND OBJECTIVE Peak oxygen consumption (pVO2 ), determined from CPET, provides a valuable indication of PAH severity and patient prognosis. However, CPET is often contraindicated in severe PAH and frequently terminated prior to achievement of a sufficient exercise effort. We sought to determine whether in PAH low-intensity [i.e. freewheeling exercise (FW)] exercise reveals abnormal VE /VCO2 and PET CO2 responses that are associated with pVO2 and serve as indices of PAH risk stratification and mortality. METHODS Retrospective analysis of CPET from 97 PAH patients and 20 age-matched controls was undertaken. FW VE /VCO2 and PET CO2 were correlated with pVO2 % age-predicted. Prognostication analysis was conducted using pVO2  > 65% age-predicted, as known to represent a low mortality risk. Primary outcome was mortality from any cause. RESULTS FW PET CO2 was correlated with pVO2 (P   65% age-predicted (best cut-off value of 28 mm Hg). By Cox analysis, FW PET CO2  < 28 mm Hg remained a predictor of mortality after adjusting for age and PAH aetiology (HR: 2.360, 95% CI: 1.144-4.866, P = 0.020). CONCLUSION Low PET CO2 during FW is associated with reduced pVO2 in PAH and provides predictive information for PAH risk stratification and prognostication.