EDN1 and hydrops fetalis: Mature and active ET-1 is finally excised from big ET-1 by the action of endothelin-converting enzyme.[7] Plasma level of ET-1 can be altered by stimuli such as hypoxia, shear stress, lipoproteins, free radicals, and endotoxin.[7] In 1995, Tsutamoto et al[10] indicated that HF patients with higher level of ET-1 had elevated risk of cardiac death.