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 (pVO(2)), 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 V-E/VCO2 and PETCO2 responses that are associated with pVO(2) 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 V-E/VCO2 and PETCO2 were correlated with pVO(2)% age-predicted. Prognostication analysis was conducted using pVO(2) > 65% age-predicted, as known to represent a low mortality risk. Primary outcome was mortality from any cause.Results FW PETCO2 was correlated with pVO(2) (P < 0.0001; r = 0.52), while FW V-E/VCO2 was not (P = 0.13; r = -0.16). ROC curve analyses showed that FW PETCO2 (AUC = 0.659), but not FW V-E/VCO2 (AUC = 0.587), provided predictive information identifying pVO(2) > 65% age-predicted (best cut-off value of 28 mm Hg). By Cox analysis, FW PETCO2 < 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 PETCO2 during FW is associated with reduced pVO(2) in PAH and provides predictive information for PAH risk stratification and prognostication.