Optimizing the evaluation of excess exercise ventilation for prognosis assessment in pulmonary arterial hypertension

Increased ventilatory ($\stackrel{·}{\text{V}}$E) response to carbon dioxide output ($\stackrel{·}{\text{V}}$CO₂) is a key finding of incremental cardiopulmonary exercise testing in both heart failure and pulmonary arterial hypertension (PAH). As with heart failure, measures of excessive exercise ventilation considering high-to-peak exercise $\stackrel{·}{\text{V}}$E–$\stackrel{·}{\text{V}}$CO₂ might have higher prognostic relevance than those restrained to sub-maximal exercise in PAH.

Cross-sectional and observational study on a tertiary center.

Eighty-four patients (36 idiopathic and 48 with associated conditions) were followed up for up to five years. Excessive exercise ventilation was calculated as a slope (Δ $\stackrel{·}{\text{V}}$E/Δ $\stackrel{·}{\text{V}}$CO₂ to the respiratory compensation point (_RCP) and to exercise cessation (_PEAK)) and as a ratio ($\stackrel{·}{\text{V}}$E/$\stackrel{·}{\text{V}}$CO₂ at the anaerobic threshold (_AT) and at _PEAK).

Thirteen patients died and three had atrial septostomy. Multivariable regression analyses revealed that Δ $\stackrel{·}{\text{V}}$E/Δ $\stackrel{·}{\text{V}}$CO_2(PEAK) <55 and $\stackrel{·}{\text{V}}$E/$\stackrel{·}{\text{V}}$CO_2(PEAK) <57 were better related to prognosis than Δ $\stackrel{·}{\text{V}}$E/Δ $\stackrel{·}{\text{V}}$CO_2(RCP) and $\stackrel{·}{\text{V}}$E/$\stackrel{·}{\text{V}}$CO_2(AT) (p < 0.01). Δ oxygen uptake ($\stackrel{·}{\text{V}}$O₂)/Δ work rate >5.5 ml/min per W was the only other independent prognostic index. According to a Kaplan–Meier survival analysis, 96.9% (90.8% to 100%) of patients showing Δ $\stackrel{·}{\text{V}}$E/Δ $\stackrel{·}{\text{V}}$CO_2(PEAK) <55 and Δ $\stackrel{·}{\text{V}}$O_2/Δ work rate >5.5 ml/min per W were free from a PAH-related event. In contrast, 74.7% (70.1% to 78.2%) with both parameters outside these ranges had a negative outcome.

Measurements of excessive exercise ventilation which consider all data points maximize the usefulness of incremental cardiopulmonary exercise testing in the prognosis evaluation of PAH.