Exercise tolerance in systemic sclerosis patients without pulmonary impairment: correlation with clinical variables

OBJECTIVES: In systemic sclerosis (SSc) patients pulmonary vasculopathy (PV) is present in the early stage of disease and impairs dilation of affected pulmonary blood vessels, impeding pulmonary blood flow during exercise. Abnormal gas exchange findings were early investigated by cardiopulmonary exercise test (CPET). METHODS: A total of 34 female and 6 male [median age 49 (20-63) years] SSc patients with normal chest imaging and pulmonary function tests were enrolled. Twenty healthy controls age and sex matched [16 female and 4 male; median age 51 (35-73) years] were also recruited. All subjects underwent a full clinical examination, including a nailfold video capillaros copy (NVC). An incremental symptom-limited CPET was performed with estimation of minute ventilation (VE), workload (WR), peak oxygen uptake (pVO₂2), and ventilatory efficiency (VE/VCO2 slope). RESULTS: A reduced exercise tolerance (pVO₂<80% of predicted) was documented in 18 out of 40 subjects (45%). Six out of 18 patients with a reduced exercise tolerance showed indirect signs of ventilation perfusion mismatch (VE/ VCO2 slope >34). Patients with digital ulcers (DUs) history showed VE/VCO₂slope values significantly higher [31.4 (18-39.6)] than in patients without DUs history [26.9 (22-29.4)] (p<0.0001). VE/VCO₂slope values also significantly differed between the three capillaroscopic groups: early [26.3 (18-29.4)], active [28 (26.8-39.6)], and late [32.9 (22.4-39)] (p<0.0001). A positive correlation was found between the VE/ VCO₂slope and both Disease Activity Index (p<0.0001, r=0.59) and Disease Severity Scale (p<0.0001, r=0.73). CONCLUSIONS:In SSc patients without evidence of pulmonary and cardiac involvement, CPET might be useful in disclosing an early PV.