TGFB1 and chronic thromboembolic pulmonary hypertension: Background and objectives: Endothelin-1 (ET-1) and transforming growth factor-β (TGF-β) play a pivotal role in the pathophysiology and vascular remodeling of chronic thromboembolic pulmonary hypertension (CTEPH) which is an under-diagnosed complication of acute pulmonary embolism (PE).