Chronic heart failure

Inclusion Criteria

- Providing signed informed consent
- Diagnosis of heart failure lasting for at least 3 months, New York Heart Association (NYHA) functional class I-III prior to Visit 1
- Left ventricular ejection fraction (LVEF) ≤ 45% as documented by any imaging modality within the past 12 months prior to Visit 1
- Treatment with Guideline-Directed Medical Therapy Including with mandatory betablocker treatment with either Metoprolol, Carvedilol, Bisoprolol or Nebivolol on stable, highest individually tolerated dose for at least 2 weeks prior to Visit 1
- Implanted cardiac defibrillator (ICD) with pacemaker backup function OR cardiac resynchronization device (CRT)
 -- first implantation at least 3 months prior to Visit 1

Exclusion Criteria

- Permanent atrial fibrillation or other than Sinus rhythm at Visit 1
- History of higher degree atrioventricular (AV) block (Mobitz type II or third-degree AV block) within 4 weeks prior to Visit 1
- Indication for or planned procedure:
 -- Planned cardiac surgery, carotid angioplasty or surgery, transcatheter aortic valve implantation (TAVI) or mitral valve clipping within 3 months starting from the Screening Visit
 -- Percutaneous coronary intervention (PCI), coronary artery bypass graft (CABG) or implantation of a cardiac resynchronization therapy defibrillator device indicated at Screening or planned within 3 months starting from the Screening Visit
 -- Valvular Disease Repair indicated at Screening or planned within 3 months starting from the Screening Visit.
- Occurrence of any of the following within 4 weeks prior to Visit 1:
 -- Myocardial infarction
 -- Stroke or transient ischemic attack (TIA)
 -- coronary artery bypass graft (CABG)
 -- percutaneous coronary intervention (PCI)
 -- Carotid angioplasty
 -- Ablation therapy of atrial fibrillation or other rhythm abnormalities
- Heart rate (HR) > 100 bpm at Screening Visit
- Restrictive, infiltrative or hypertrophic cardiomyopathy, constrictive pericarditis, acute myocarditis within 3 months prior to Visit 1
- Malignancy of the hematological system within 5 years prior to the Screening Visit
- Listed for heart transplantation and/or anticipated implantation of a ventricular assist device at the Screening Visit
- Hepatic insufficiency classified as Child-Pugh B or C at the Screening Visit
- Estimated (according to the investigator’s judgement) inability to perform exercise testing
- Any of the following from the blood sample taken at the Screening Visit
 -- Estimated glomerular filtration rate (eGFR) < 30 mL/min/1.73 m^2 (calculated according to the Chronic Kidney Disease Epidemiology Collaboration [CKD-EPI] equation)
 -- Hemoglobin < 11 g/dL 
 -- White blood cell (WBC) < 3000/mm^3
 -- Thrombocytes < 100 000/mm^3
- Currently receiving or planned to receive dialysis or ultrafiltration
- Chronic obstructive pulmonary disease (COPD) Stage 3 or 4 (GOLD criteria), requiring treatment, or symptomatic asthma requiring current treatment
- Prior or concomitant therapy with cytochrome P450 isoenzyme 3A4 (CYP3A4) inhibitors or inducers. 
    Relevant substances need to be discontinued
 -- at least 2 weeks before randomization for CYP3A4 inducers
 -- at least 5 half-lives before randomization for CYP3A4 inhibitors
    Restarting of these therapies is possible 28 days after last intake of study intervention. This criterion also applies to other inhibitors of CYP3A4, e.g., grapefruit.
    Prior and concomitant therapy with amiodarone is allowed.
- Concomitant treatment with acetylcholine esterase inhibitors within 4 weeks prior to Visit 1
- Use of other investigational drugs. Previous (within 4 weeks, or 5 half-lives of the investigational drug, whichever is longer, prior to Visit 1) or concomitant participation in another clinical study with investigational medicinal product(s) or device(s)
- Life expectancy < 6 months at the Screening Visit