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 PETCO2 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 PETCO2 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 PETCO2 was correlated with pVO2 (P < 0.0001; r = 0.52), while FW VE/VCO2 was not (P = 0.13; r = −0.16). ROC curve analyses showed that FW PETCO2 (AUC = 0.659), but not FW VE/VCO2 (AUC = 0.587), provided predictive information identifying pVO2 > 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 pVO2 in PAH and provides predictive information for PAH risk stratification and prognostication. [ABSTRACT FROM AUTHOR]