EDN1 and chronic thromboembolic pulmonary hypertension: Regarding the potential correlation between the preoperative levels of ET-1 and TGF-β with clinical symptoms of patients with CTEPH awaiting surgical correction, it was curious to notice the lack of correlation between the preoperative levels of both ET-1 and TGF-β and the hemodynamic parameters evaluating the degree of severity of pulmonary hypertension in patients presenting with severe functional limitations (WHO class III and IV).