Background: Many studies have highlighted sex preponderance in idiopathic pulmonary arterial hypertension (IPAH). It is well established that there are differences in exercise capacities in the two sexes but how much of that difference reflects on disease severity or correlates to markers of severity in the two sexes is still not clear. Right heart catheterization (RHC) and cardiopulmonary exercise testing (CPET) have been widely used for assessing functional capacity, prognosis and treatment response in IPAH. We aimed to investigate the 'sex-specific' CPET parameters in relation to hemodynamics in IPAH.
Methods: Data were retrieved from 30 males and 53 females [mean ± standard deviation (SD) age: 39.6 ± 17.2 and 37.5 ± 12.0] stable IPAH patients who underwent both RHC and CPET at Shanghai Pulmonary Hospital from 2010 to 2016. Univariate and forward/backward multiple stepwise regression analysis was performed to assess the prognostic value of CPET and hemodynamic parameters.
Results: There were no significant differences in clinical variables between men and women. Peak workload, peak oxygen uptake, anaerobic threshold (AT), peak minute ventilation, carbon dioxide output, O2 pulse and oxygen uptake efficiency slope were significantly higher in men compared with women ( p < 0.05). Several CPET indexes correlated with hemodynamics. Pulmonary vascular resistance (PVR) and cardiac output (CO) were distinctly different between the sexes. Peak end-tidal partial pressure of CO2 (PETCO2) was an independent predictor of PVR elevation in all patients and in men. Peak maximum oxygen consumption (VO2) was independently predictive of CO decline in all patients and in men. Only peak O2 pulse was an independent predictor of increased PVR and decreased CO in women.
Conclusions: Even after adjusting for age, body mass index and World Health Organization functional class, different CPET parameters correlated with PVR elevation and CO decline in men and women differently, which could potentially better predict severity in men and women with IPAH.
Keywords: CO; CPET; IPAH; PVR; sex difference.