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

Abstract

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 VEVCO2 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 (δVE/δVCO2 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 δVE/δVCO2 (PEAK) <55 and VE/δVCO2(PEAK) <57 were better related to prognosis than δVE/δ VCO2(RCP) and VE/ δVCO2(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 KaplanMeier survival analysis, 96.9% (90.8% to 100%) of patients showing δVE/δ VCO2 (PEAK) <55 and δVE/δ VCO2 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.