IGF1 and hydrops fetalis: Furthermore, three studies compared IGF-1 levels between HFrEF and HFpEF patients (30, 32, 33), four studies compared IGF-1 levels between HF patients classified as NYHA grade III–IV and those classified as NYHA grade I–II (31, 39–41), and four studies compared IGF-1 levels between non-survivors and survivors of HF (38, 40, 42, 43).