SLC5A2 and hydrops fetalis: We enrolled HF reduced ejection fraction (LVEF) outpatients (EF <40%) eligible for SGLT2-i and performed cardiopulmonary exercise tests (CPET), pulmonary function tests, bioelectrical impedance vector analysis, and laboratory and echocardiographic assessments at baseline (T = 0), after 2–4 weeks (T1), and after 6 months of treatment (T2).