The level of recruitment, 62 participants enrolled, does not allow for achieving the protocol-defined target of 350 participants by the end of the recruitment period.

The objective of the study is to determine the efficacy of repeated infusions of levosimendan in the group of outpatients with advanced systolic heart failure (HF).

It is a multicentre, randomized, double-blind, placebo-controlled study. 350 subjects will be included (in 12 or more medical centers) with severe HF, ejection fraction ≤35%, in New York Heart Association class III or IV. The other inclusion criteria concern: hospitalization for the HF decompensation in the last 3 months and a reduced six-minute walk test <350m or elevated NTproBNP ≥1000 pg / mL. To the European Society of Cardiology-guided, individually optimized medical therapy (OMT) the investigational product (IP) will be added. The subjects will be randomly assigned to one of the study group: 175 to the levosimendan arm and 175 to the placebo arm. The intervention studied in LEIA-HF trial is the administration of levosimendan as a continuous iv. infusion, every 4 weeks for 48 weeks (12 infusions in total). All study participants will also continue OMT. In the second phase of the study, after completing the levosimendan / placebo infusions, another 6 visits are planned, still double-blind, every 4 weeks, to assess the safety of treatment discontinuation (with optional return to the infusions by the Investigator when additional criteria for HF decompensation are met).

The efficacy of the treatment will be assessed after 52 weeks, 4 weeks after the last levosimendan / placebo administration.

Inclusion Criteria:

• Informed consent obtained before any trial activities
• Male or female, age ≥ 18 years at the time of signing informed consent
• Left ventricle ejection fraction ≤ 35%
• Hospitalization due to worsening of HF within the last 3 months
• New York Heart Association functional class III or outpatient IV
• Individually optimized pharmacotherapy, based on the current European Society of Cardiology recommendations, stable for at least 1 month prior to randomization, according to the knowledge and experience of the qualifying clinician
• Distance covered in six-minute walk test <350m OR NTproBNP concentration ≥ 1000 pg/mL
• In the opinion of the Investigator, the patient does not currently require hospitalization
• Patient protected with an implantable device capable of terminating life-threatening arrhythmias and conduction disturbances (ICD or cardiac resynchronisation therapy-D/P), if indicated and the patient consents to implantation.

Exclusion Criteria:

• Known or suspected hypersensitivity to trial products or related products,
• Restrictive or hypertrophic cardiomyopathy, uncorrected severe valvular disease, potentially reversible cause of HF
• Hypotension with symptoms of tissue hypoperfusion
• Uncontrolled hypertension
• Planned revascularization or other surgical treatment of HF within the next year
• Advanced chronic kidney disease
• Features of liver damage
• Severe chronic lung disease with features of respiratory distress or severe abnormal spirometry or home oxygen treatment
• Accompanying chronic diseases with poor prognosis
• Paroxysmal supraventricular tachycardia, paroxysmal ventricular tachycardia, torsade de pointes, advanced atrioventricular blocks within one month prior to screening
• Receipt of any investigational product within 30 days before screening visit
• Any disorder, which in the investigator's opinion may jeopardise subject's safety or compliance with the study protocol and procedures

According to the agreement with the funding institution (Medical Research Agency), the sponsor and research centers must obtain the consent of the funding institution to disclose the clinical trial data.