Phenotyping Exercise Limitation in Systemic Sclerosis: The Use of Cardiopulmonary Exercise Testing

Exercise impairment is a common symptom of systemic sclerosis (SSc), a disorder which is frequently complicated by cardiopulmonary involvement.

This study's aims were: (a) to define the prevalence and the potential causes of limited exercise capacity and (b) to study potential differences in clinical, radiological and functional characteristics and blood serology among SSc patients with exercise limitation of different etiology.

Prospectively collected data on SSc patients who had conducted full lung function testing, blood serology, thorax high-resolution computed tomography, Doppler echocardiogram and a maximal cardiopulmonary exercise testing (CPET) were retrospectively analyzed. Using a CPET algorithm, patients were characterized as having normal or subnormal exercise capacity (N), respiratory limitation (RL), left ventricular dysfunction (LVD) or pulmonary vasculopathy (PV). Group comparisons were conducted using either one-way ANOVA or the Kruskal-Wallis test. A p value <0.05 was considered significant.

The study population consisted of 78 patients (53.7 ± 13.7 years old; 10.3% male). PV was present in 32.1%, LVD in 25.6% and RL in 10.2%, while 32.1% of the patients constituted the N group. The presence of antisclero-70 antibodies, low anaerobic threshold and low peak exercise capacity measures could discriminate LVD from the other groups. Low end-tidal carbon dioxide pressure and its change from rest to anaerobic threshold could discriminate between the PV, LVD and N groups, while respiratory restriction along with ventilatory inefficiency indices could differentiate the RL group from the rest.

The combined evaluation of CPET gas exchange patterns with baseline measurements could discriminate the causes of exercise limitation among SSc patients.