A Study to Learn More About How Well Finerenone Works, How Safe it is, and How it Moves Into, Through, and Out of the Body Compared to Placebo When Taken With Standard Treatment in Children With Heart Failure and Left Ventricular Systolic Dysfunction

Inclusion Criteria: * Participants must be 6 months to \<18 years old at the time when the informed consent/assent is signed. * Left ventricular systolic dysfunction (LVSD) with left ventricular ejection fraction (LVEF) ≤ 50% at screening assessed by echocardiography. * Elevated NT-pro BNP levels * \>500 ng/l for children ≥ 6 months to \< 2 years of age * \>300 ng/l, for children ≥ 2 years to \<18 years * Heart failure etiologies including congenital heart defects (CHD) with biventricular physiology and systemic LV; idiopathic cardiomyopathy (CM); familial/inherited and/or genetic CM; history of myocarditis (diagnosis of an acute episode was at least 3 months prior to randomization); neuromuscular disorder (eg, duchenne muscular dystrophy); inborn error of metabolism; mitochondrial disorder; acquired (chemotherapy, iatrogenic, infection, rheumatic, or nutritional); ischemic (eg, Kawasaki disease and postoperative heart failure \[HF\]); LV noncompaction. * Receiving standard of care (SoC) treatment for heart failure according to local guidelines or investigator´s discretion and being on a stable regimen for 30 days prior to randomization. * Study participants must have a body weight ≥ 4.0 kg at Visit 1. Exclusion Criteria: * Serum/plasma potassium (based on local laboratory results): * \> 5.0 mmol/L for children ≥ 2 years of age at either screening or randomization visit * \> 5.3 mmol/L for children ≥ 6 months to \< 2 years of age at either screening or randomization visit (if estimated glomerular filtration rate \[eGFR\] \< 60 mL/min/1.73m², threshold of \> 5.0 mmol/L will be used) * Severe renal dysfunction with eGFR \< 30 mL/min/1.73m² at randomization visit based on local laboratory results. * Systolic blood pressure (SBP) \< 5th percentile for age, sex and height at screening or randomization. * Sustained or symptomatic arrhythmias not controlled by drug or device therapy within 30 days prior to randomization. * Treatment with a mineralocorticoid receptor antagonist (e.g., spironolactone, eplerenone) within 30 days of randomization. * Requirement of any intravenous (IV) vasoactive agents, mechanical ventilation, mechanical circulatory support within 30 days prior to randomization. * Recent surgical procedure or other intervention to correct or palliate CHD within 3 months prior to randomization or anticipated to undergo cardiac surgery during the 3 months after randomization.