Exercise pathophysiology differs between connective tissue diseases-associated pulmonary arterial hypertension and idiopathic pulmonary arterial hypertension.

Objectives Previous studies demonstrated that connective tissue diseases-associated pulmonary arterial hypertension (CTD-PAH) had a worse prognosis than idiopathic pulmonary arterial hypertension (IPAH), although the former one had better haemodynamic profiles and right heart function. To find potential explanations for this contradictory phenomenon, we compared the exercise pathophysiology of CTD-PAH with that of IPAH using cardiopulmonary exercise testing (CPET). Methods Ninety-three CTD-PAH patients were retrospectively enrolled and matched 1:1 with 93 IPAH patients according to age, gender, body mass index, and body surface area. Multiple linear regression analysis was performed to adjust confounding factors. Results CTD-PAH had higher rest heart rate (HR@Rest) and lower rest oxygen uptake/HR (VO2/HR@Rest) than IPAH. During exercise, the peak power (Power@Peak), VO2@Peak, peak metabolic equivalents (METS@Peak), peak minute ventilation (VE@Peak), peak tidal volume (VT@Peak), HR@Peak, peak systolic blood pressure (SBP@Peak) and peak diastolic blood pressure (DBP@Peak) of CTD-PAH were lower than those of IPAH. After adjustment, CTD-PAH still had lower values of Power@Peak, VO2@Peak, METS@Peak, VT@Peak, VO2/HR@Rest, DBP@Peak and had higher HR@Rest than IPAH. Conclusions CTD-PAH had more impaired ventilation, cardiac function and muscular strength (reflected by CPET-derived parameters) than IPAH, in despite of better haemodynamic profiles and comparable heart structure (assessed by echocardiography) and functional status (indicated by World Health Organisation functional class, N-terminal pro-brain natriuretic peptide and six-minute walk distance).