Big endothelin-1 and endothelin-1 plasma levels are correlated with the severity of primary pulmonary hypertension

Study objectives: Primary pulmonary hypertension (PPH) is a rare disease of unknown etiology that is characterized by a poor prognosis. This study was undertaken to investigate possible correlations between endothelin (ET)-1 and big ET-1 plasma levels and the severity of PPH. Patients: Sixteen consecutive patients with PPH were included. Interventions: Hemodynamics of patients with PPH were measured by right-heart catheterization, and a 6-min walk test was performed. Measurements: Plasma levels of the biologically active peptide ET-1 and its precursor big ET-1 were determined in blood samples from the pulmonary artery, peripheral artery, and peripheral vein by radioimmunoassay. Results: A strong correlation was shown between pulmonary vascular resistance, mean pulmonary artery pressure, cardiac output, cardiac index, 6-min walk data, and elevated plasma levels of big ET-1 as well as mature ET-1 plasma levels at all sites of blood sampling (p<0.01 and p<0.05, respectively). Conclusions: Levels of circulating ET-1 might become a prognostic marker for patients with PPH and serve as a tool for the selection of patients who may benefit from treatment with ET-receptor antagonists.