Value of cardiopulmonary exercise testing in comparing cardio-pulmonary function among patients with three kinds of pulmonary artery hypertension

Objective: To assess the exercise capacity of three kinds of pulmonary artery hypertension using cardiopulmonary exercise testing (CPET).

Methods: In the Center for Pulmonary Vascular Disease Diagnosis and Treatment of Fuwai Hospital, idiopathic pulmonary artery hypertension (IPAH), congenital heart disease associated pulmonary artery hypertension (CHD-PAH), connective tissue disease associated pulmonary artery hypertension (CTD-PAH) were enrolled into this study from December 2012 to May 2013. CPET was performed in all patients, and clinical features, routine tests results, N-terminal B-type natriuretic peptide (NT-proBNP), Six-minutes-walk distance (6MWD) were all collected.

Results: Thirty-two patients with IPAH, 38 patients with CHD-PAH, 25 patients with CTD-PAH were enrolled. For IPAH, CHD-PAH, and CTD-PAH patients, the peak oxygen uptake via body weight (VO₂max/kg) was (12.3 ± 2.3), (14.9 ± 4.0), and (11.1 ± 2.5) ml·min⁻¹·kg⁻¹, respectively. The peak VO₂/kg was significantly different within these three groups (P<0.001), and was significantly higher in CHD-PAH patients compared with the other two groups (P=0.003, P<0.001). The peak VO2/heart rate (HR) was (5.8±1.4), (6.4 ± 1.8), (5.3 ± 1.7) ml·beat(-1)·min⁻¹ in the above three groups and was significantly different within these three groups (P=0.034). The peak VO₂/HR was significantly increased in CHD-PAH patients than CTD-PAD patients (P=0.012). The peak HR was (136.1 ± 21.4), (140.8 ± 19.9), (124.5 ± 21.6) beat/min respectively and was significantly lower in CTD-PAD patients than CHD-PAH patients (P=0.009). The 6MWD was significantly decreased in CTD-PAD patients compared with CHD-PAH and IPAH patients (P=0.006, 0.010). Nt-proBNP was significantly decreased in CTD-PAD patients compared with CHD-PAH patients (P=0.012). In Pearson and partial correlation analysis, the peak VO₂/kg was significantly correlated with peak VO₂/HR, peak HR, 6MWD, Nt-proBNP, left ventricular end-diastolic diameter, right ventricular end-diastolic diameter (r=0.477, 0.518, 0.387, 0.465, -0.350, 0.349, -0.259).

Conclusions: CPET parameters can objectively evaluate exercise capacity and cardiopulmonary function of the patients with pulmonary hypertension.