Interstitial lung disease and pulmonary hypertension are the leading causes of morbidity and mortality in patients with systemic sclerosis (SSc). Exercise-induced dyspnea is the first manifestation of both complications, which explains why the value of resting tests to predict preclinical heart or lung involvement is limited. Cardiopulmonary exercise testing (CPET) offers a comprehensive approach to identify the cause of exercise limitation. However, the role of CPET in SSc patients without demonstrated cardiac and/or respiratory disease has not been extensively investigated.

We sought to compare the cardiopulmonary adaptation to exercise of SSc patients without cardiac or pulmonary disease vs. healthy controls.

SSc patients with normal resting echocardiography and pulmonary functional test, and healthy volunteers were prospectively enrolled. All underwent maximal CPET and results were compared after correction for age and gender.

Thirty-nine patients (females 36, age 54±12) and 43 healthy subjects (females 31, age 46±11) were included between 07/2015 and 05/2018. Exercise capacity was lower in patients than in healthy subjects (Table 1). Patients had lower oxygen uptake (VO2) at peak exercise and higher minute ventilation/carbon dioxide production (VE/VCO2) slope than controls (Figure 1). They had higher VE/VCO2 ratio and lower end-tidal pressure of CO2 (PetCO2) at the ventilatory threshold. Ventilatory reserve was preserved and peripheral oxygen saturation was normal in both groups.

The combination of low peak VO2, high VE/VCO2 slope, low PetCO2, and high respiratory reserve suggest that patients with SSc without overt cardiac or respiratory disease present with a cardiovascular limitation to exercise. The latter may be related to latent cardiac dysfunction or pulmonary vascular disease.