This systematic review aims to assess the correlation strength between EFT and BNP/NT-proBNP levels in HF and at-risk populations, evaluate how this relationship varies by HF phenotype (HFrEF vs. HFpEF), determine their combined prognostic accuracy in HF risk stratification, and identify methodological limitations and underexplored areas to guide future research. Here, NPPB is linked to hydrops fetalis.