Inclusion Criteria:  Female or male patient, aged 18 years or older at the time of HF diagnosis Diagnosis of heart failure with reduced ejection fraction confirmed by echocardiography Patient on HFrEF standard of care treatment with guideline-based therapy One or more HF decompensation(s) within observation period defined as HFH or the need for IV diuretic treatment Signed informed consent if patient is alive at start of data collection  At least one NT-proBNP value available prior enrollment, fulfilling the below criteria:  NT-proBNP value was assessed in an outpatient setting exactly at 01-JAN-2016 or later NT-proBNP value was assessed and within six months after a decompensation event within observational period. At time of NT-proBNP measurement patients need to be hemodynamically stable without signs of residual congestion  Exclusion Criteria:  At time of NT-proBNP measurement  Participation in an investigational program with interventions outside of routine clinical practice Awaiting heart transplantation or has/anticipates receiving an implanted ventricular assist device Has acute coronary syndrome (unstable angina, non-ST elevation myocardial infarction, or ST elevation myocardial infarction) or coronary revascularization (coronary artery bypass grafting or percutaneous coronary intervention) Estimated glomerular filtration rate (eGFR) calculated based on the Modification of Diet in Renal Disease (MDRD) equation < 15 ml/min/1.73m2 or chronic dialysis Severe hepatic insufficiency (CHILD Pugh C) Acute inflammatory disease Malignancy Treatment with Vericiguat (which may be available to patients in Germany in Q3 2021 but not at time of protocol development)