IL1RL1 and hydrops fetalis: Another study aimed to compare ST2 concentrations in patients with left ventricular systolic dysfunction from nonvalvular causes and patients with severe AS and found that sST2 levels did not differ significantly between patients with HF and patients with AS and normal EF (EF ≥ 50%); however, in AS patients with low EF (EF < 50%), ST2 concentrations were significantly higher than that of the HF group [78].