Factors limiting exercise performance in progressive systemic sclerosis

In order to evaluate to which extent various organs limit physical performance in PSS, maximal working capacity was studied in 22 patients. Special attention was given to cardiac and pulmonary function, joint mobility, and muscular strength. A model for scoring these parameters is given. Working capacity was on the average 51% of the predicted normal value. Ventilation at maximal workload was high despite normal arterial blood gases and presumably normal physiologic dead space. This can be explained by an increased demand on ventilation from an increased muscle metabolism. This may be due to impeded mobility of respiratory and locomotive organs. The maximal heart rate was low and patients with low physical capacity had only a small decrease in base excess. One third of the patients developed arrhythmia during exercise, which contributed to a low performance. Other myocardial involvement was common, seen in the Q-waves, low voltage, left axis deviation, and increased heart volume. In PSS, these ECG changes probably reflect myocardial fibrosis that has developed without clinically manifest infarction. Special attention must be given to arrhythmias at work, which are overlooked in a resting ECG. Ventricular tachycardia plays an important role in sudden death, which, when it occurs, almost always does so within the first years after the onset of PSS. There was no close linkage between cardiac dysfunction and pulmonary fibrosis or joint-muscle impairment. The scoring system showed an equal distribution in reduction of working capacity as to circulation, pulmonary function, and locomotive function.+2