Prognostic value of cardiopulmonary exercise testing in pulmonary arterial hypertension

Current guidelines recommend a four-strata model based on World Health Organization Functional Class (WHO FC), 6-min walk distance (6MWD) and serum levels of brain natriuretic peptide (BNP) or N-terminal pro-BNP (NT-proBNP) for risk stratification in patients with pulmonary arterial hypertension (PAH) during follow-up. We explored the relevance of using cardiopulmonary exercise testing (CPET) as the exercise parameter in place of 6MWD at first reassessment after treatment initiation in PAH.

Incident treatment-naive patients with idiopathic, heritable, drug/toxin-induced and connective tissue disease-associated PAH between 2010 and 2022 were analysed. Correlations between CPET and haemodynamic and right ventricular function parameters were explored, and those which were significant were carried forward to assess association with survival. Independent predictors were used to derive a four-strata CPET score.

262 patients were included. CPET parameters showed better correlations with haemodynamics and right ventricular function than 6MWD. The CPET score included peak oxygen uptake (peak V̇ _O2 ), the slope relating minute ventilation to carbon dioxide production (V̇ _E/V̇ _CO2 slope) and peak oxygen pulse. The four-strata model based on WHO FC, BNP and CPET score predicted survival at the time of the first re-evaluation, with better accuracy than the model including 6MWD (C-index 0.81 versus 0.71). The CPET score on its own also performed well (C-index 0.82) with a greater spread between categories. Treatment-associated changes in peak V̇ _O2 predicted survival, while changes in 6MWD did not.

A simplified four-strata CPET score either alone or included with BNP and WHO FC accurately predicts survival at follow-up in PAH.