NPPB and hydrops fetalis: In contrast to ET-1 and big ET-1, circulating CT-proET-1 level is higher (∼80 pmol/L) and less cross-react with other ET-1 peptides.[12,50] CT-proET-1 is stable and more resistant to rapid turnover both in vivo and in vitro, which makes it easier to obtain reliable results.[50] BNP and NT-proBNP are regarded as the pivotal markers for the diagnosis and prognosis of HF.