Short-term Effects of Dapagliflozin on Peak VO2 in HFrEF

Inclusion Criteria: * The participant or his legal representative is willing and able to give informed consent for participation in the study. * Male or female, aged ≥18 years. * Established documented diagnosis of symptomatic HF (NYHA functional class II-III), which has been present for at least 2 months. * LVEF ≤40% documented in the last 3 months by echocardiography or cardiac magnetic resonance. * NT-proBNP ≥600 pg/ml. * Patients should receive background standard of care for HFrEF at judgment of the investigator. * Estimated glomerular filtration rate (eGFR) ≥30 ml/min/1.73m2 (DMRD formula) at enrolment. Exclusion Criteria: * Inability to perform a valid (respiratory exchange ratio -RER- ≥1.05) baseline cardiopulmonary exercise test (CPET) * Patients receiving therapy with an SGLT2 inhibitor within 8 weeks prior to enrolment, or previous intolerance of an SGLT2 inhibitor * Type 1 diabetes * Symptomatic hypotension or systolic blood pressure \<95 mmHg * Current acute decompensated HF or hospitalization due to decompensated HF \<4 weeks prior to enrolment * Myocardial infarction, unstable angina, stroke, or transient ischemic attack within 12 weeks prior to enrolment * Coronary revascularization (percutaneous coronary intervention or coronary artery bypass grafting) or cardiac valve repair/replacement within 12 weeks prior to enrolment, or planned to undergo any of these operations after randomization * Implantation of a cardiac resynchronization therapy (CRT) device within 12 weeks prior to enrolment or intent to implant a CRT device * Previous cardiac transplantation or implantation of a ventricular assistance device or similar device, or implantation expected after randomization * HF due to restrictive cardiomyopathy, active myocarditis, constrictive pericarditis, hypertrophic (obstructive) cardiomyopathy, or uncorrected severe primary cardiac valve disease * Symptomatic bradycardia or second or third-degree heart block without a pacemaker * Severe renal dysfunction (eGFR\<30 ml/min/1.73m2) or prior admission for acute renal failure in the last 4 weeks. * Pregnant or lactating women * Woman of childbearing age, unless they are using highly effective contraceptive methods. * Patients with severe hepatic impairment (Child-Pugh class C).