NPPB and hydrops fetalis: In 2331 CHF patients (left ventricular ejection fraction < 35%) in the US HF-ACTION study with a median baseline sST2 level of 23.7 ng/ml (IQR: 18.6-31.8) [29], the sST2 level was found to be independently associated with HF patients' prognosis in the multivariate model after adjustment for covariates and NT-proBNP.