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

BACKGROUND: Increased ventilatory (.VE) response to carbon dioxide output (.VCO2) 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 .VE-VCO2 might have higher prognostic relevance than those restrained to sub-maximal exercise in PAH. DESIGN: Cross-sectional and observational study on a tertiary center. METHODS: 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 .VE/Δ .VCO2 to the respiratory compensation point (RCP) and to exercise cessation (PEAK)) and as a ratio (.VE-VCO2 at the anaerobic threshold (AT) and at PEAK). RESULTS: Thirteen patients died and three had atrial septostomy. Multivariable regression analyses revealed that Δ .VE/Δ .VCO2(PEAK) <55 and .VE/.VCO2(PEAK) <57 were better related to prognosis than Δ .VE/Δ .VCO2(RCP) and .VE/.VCO2(AT) (p < 0.01). Δ oxygen uptake (.VO2)/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 .VE/Δ .VCO2(PEAK) <55 and Δ .VO2/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. CONCLUSION: Measurements of excessive exercise ventilation which consider all data points maximize the usefulness of incremental cardiopulmonary exercise testing in the prognosis evaluation of PAH.