Impaired right ventricular lusitropy is associated with ventilatory inefficiency in pulmonary arterial hypertension

Cardiopulmonary exercise testing (CPET) is an important tool for assessing functional capacity and prognosis in pulmonary arterial hypertension (PAH). However, the associations of CPET parameters with the adaptation of right ventricular (RV) function to afterload remain incompletely understood.In this study, 37 patients with PAH (idiopathic in 31 cases) underwent single-beat pressure-volume loop measurements of RV end-systolic elastance (Ees), arterial elastance (Ea) and diastolic elastance (Eed). Pulmonary arterial stiffness was assessed by magnetic resonance imaging. The results were correlated to CPET variables. The predictive relevance of RV function parameters for clinically relevant ventilatory inefficiency, defined as minute ventilation/carbon dioxide production (V' E/V' CO2 ) slope >48, was evaluated using logistic regression analysis.The median (interquartile range) of the V' E/V' CO2 slope was 42 (32-52) and the V' E/V' CO2 nadir was 40 (31-44). The mean±sd of peak end-tidal carbon dioxide tension (P ETCO2 ) was 23±8 mmHg. Ea, Eed and parameters reflecting pulmonary arterial stiffness (capacitance and distensibility) correlated with the V' E/V' CO2 slope, V' E/V' CO2 nadir, P ETCO2 and peak oxygen pulse. RV Ees and RV-arterial coupling as assessed by the Ees/Ea ratio showed no correlations with CPET parameters. Ea (univariate OR 7.28, 95% CI 1.20-44.04) and Eed (univariate OR 2.21, 95% CI 0.93-5.26) were significantly associated with ventilatory inefficiency (p<0.10).Our data suggest that impaired RV lusitropy and increased afterload are associated with ventilatory inefficiency in PAH.