Incremental value of cardiopulmonary exercise testing in intermediate-risk pulmonary arterial hypertension

Risk assessment in pulmonary arterial hypertension (PAH) is essential for prognostication. However, the majority of patients end-up in an intermediate risk status, offering insufficient guidance in clinical practice. The added value of cardiopulmonary exercise testing in this setting remains undefined. Two independent cohorts with idiopathic PAH at intermediate risk were used to develop (n = 124) and externally validate (n = 143) the prognostic model. Cross-validation on the overall population was used to strengthen the results of the analysis. Risk assessment was based on the simplified version of the ESC/ERS guidelines score. Discrimination and calibration were assessed. A risk score was constructed based on the beta-coefficient of the cross-validated model, including the stroke volume index (SVI) and the peak oxygen uptake (VO2 peak). Patients were grouped based on cutoff values of the risk score allowing the highest discrimination in the overall cohort. Group 1, score ≤2 (101 patients) with VO2 peak ≥14 ml/kg/min and SVI >30 ml/m2; Group 2, score between 2 and 5 (112 patients) with VO2 peak between 9 and 14 ml/kg/min, and SVI between 20 and 50 ml/m2; Group 3, score >5 (46 patients) with VO2 peak