Exercise-induced increase of the pulmonary arterial pressure may be an early sign of
pulmonary arterial hypertension. It has been shown that patients with normal pulmonary
arterial pressure at rest but elevated pulmonary arterial pressure during exercise have a
decreased exercise-capacity and may have a worse prognosis compared to patients with normal
pulmonary arterial pressure values at rest and during exercise. According to the currently
used definition pulmonary hypertension can be diagnosed if the mean pulmonary arterial
pressure is higher than 25mmHg at rest or 30mmHg during exercise. In this study patients with
a risk for pulmonary arterial hypertension (connective tissue disease) and increased
pulmonary arterial pressure values during exercise are receiving a therapy with a dual
endothelin receptor antagonist - bosentan, a therapy established for pulmonary arterial
hypertension. The therapy effect is than compared to the recorded changes before the
introduction of this therapy.