The study serves the identification of early forms of pulmonary arterial hypertension (PAH) in connective tissue disease and the hemodynamic follow-up of the investigated patients. The basic hypothesis is that PAH may start with a remodeling of small pulmonary arteries, which leads to a stiffening of the vessels, indicated by the inability to vasodilatation and thus a disproportional increase in pulmonary pressure during exercise. Recent studies have shown that a proportion of such patients may develop manifest PAH within a few years. The early identification of these patients and the understanding of the natural course of the disease may improve prognosis. The aim of the present study is to investigate hemodynamic and clinical changes in patients with connective tissue disease in a time interval of 3-5 years with a focus on the development of pulmonary hypertension.