[Clinical observation of cardiopulmonary exercise test in patients with idiopathic pulmonary arterial hypertension].

Objective: To explore the exercise characteristics of patients with idiopathic pulmonary arterial hypertension (IPAH).

Methods: From November 2010 to September 2012 , 76 consecutive IPAH patients and 24 healthy controls from Fuwai Cardiovascular Hospital were enrolled to undergo cardiopulmonary exercise testing. The exercise parameters were compared. Correlations among peak oxygen consumption, anaerobic threshold, peak oxygen pulse, New York Heart Association (NYHA) class, N-terminal pro-brain natriuretic peptide (NT-proBNP), 6-minute walking distance (6 MWD) and cardiac index are analyzed in IPAH.

Results: There were 21 males and 55 females in IPAH and 8 males and 16 females in controls. Their mean ages were (31.5 ± 10.6) and (35.5 ± 6.4) years respectively. Significant differences (P = 0.000) existed between two groups in peak oxygen consumption ((12.7 ± 3.3) vs (25.6 ± 5.8) ml·min(-1)·kg(-1)), anaerobic threshold ((9.8 ± 2.5) vs (16.7 ± 3.9) ml·min(-1)·kg(-1)), peak oxygen pulse ((5.3 ± 1.6) vs (9.9 ± 2.5) ml/bpm) and ventilator efficiency (slope of minute ventilation in relation to CO2 produced) ((42.6 ± 2.0) vs (25.5 ± 3.5)). In IPAH, peak oxygen consumption was significantly correlated with NYHA class (r = -0.509, P = 0.000), 6 MWD (r = 0.443, P = 0.002) and NT-proBNP levels (r = -0.423, P = 0.011). And anaerobic threshold was significantly correlated with NYHA class (r = -0.362, P = 0.002), 6MWD (r = 0.343, P = 0.004) and NT-proBNP levels (r = -0.275, P = 0.017). Peak oxygen pulse and ventilator efficiency were both correlated well with total pulmonary vascular resistance. Partial correlation analysis demonstrated that there were significant correlations among peak oxygen consumption, anaerobic threshold, NYHA class, NT-proBNP levels and 6MWD after adjusting for age, gender and weight.

Conclusions: Peak oxygen consumption and anaerobic threshold decrease ventilator efficiency in IPAH patients. Cardiopulmonary exercise testing is an invasive tool of assessing safely the function of IPAH patients.