A Study to Learn More About How Safe Finerenone is, When it is Taken for a Longer Time With Standard Treatment, in Children and Young Adults With Heart Failure and Left Ventricular Systolic Dysfunction

Researchers are looking for a better way to treat children and young adults who have heart failure with left ventricular systolic dysfunction (LVSD). Heart failure with left ventricular systolic dysfunction (LVSD) is a condition where the left side of the heart is weak and struggles to pump blood effectively, leading to symptoms like shortness of breath, fatigue, and poor growth. The study treatment, finerenone (also called BAY94-8862), is under development to treat newborns, children, and young adults with heart failure and LVSD. It works by blocking a protein that contributes to inflammation, scarring, and thickening in the heart and blood vessels, which may help the heart pump more blood effectively. The main purpose of this study is to learn about how safe finerenone is and how well it works in the long-term treatment of heart failure and LVSD. To understand how safe the treatment is, the study team will gather information on the number of patients who experience medical problems after taking finerenone, also known as "treatment emergent adverse events" (TEAEs). Additionally, they will collect blood samples to measure levels of an electrolyte called potassium and monitor blood pressure. They will also assess kidneys function using the estimated glomerular filtration rate (eGFR). In this study, which is an extension of the earlier done FIORE study, finerenone will also be studied in newly enrolled newborns under 6 months with heart failure and LVSD and children and young adults from the FIORE study. The participants will be aged from newborns up to 18 years. All the participants will continue to receive their standard treatment as routine care for heart failure, along with finerenone during the study. The participants will be in the study for around 10 to 11 months, depending on whether they rolled-over from the FIORE study or are newly enrolled newborns and infants \<6 months of age. They will take study treatment for up to 9 months. During this period, at least 6 visits are planned for participants. During these visits, the study team will: * have their blood pressure, heart rate, temperature, respiratory rate, height and weight measured * have blood samples taken * have physical examinations * have their heart examined by an electrocardiogram and echocardiography * answer questions about their medication and whether they have any adverse events, or have their parents or guardians' answer * for newborns and infants, evaluate the acceptability of the study drug formulation through parents or guardians' feedback. An adverse event is any medical problem that a participant has during a study. Doctors keep track of all adverse events that happen in studies, even if they do not think the adverse events might be related to the study treatments. The doctors will check the participants' health a month after the participants take their last treatment.