Eligibility was assessed at the screening phase, once the written informed consent was obtained. Inclusion criteria for this study were: age over 18 years, left ventricular ejection fraction (LVEF) of less than 35% measured in the previous 6 months and clinical diagnosis of advanced chronic HF (Metra M et al. Eur J Heart Fail 2007; 9(6-7):684-694)according to the following criteria: a) presence for >3 months of typical signs and symptoms of HF b) persistent ambulatory NYHA functional class III or IV for the last 4 weeks, c) no signs of congestion or low cardiac output at the time of enrolment, d) episodes of pulmonary and/or systemic congestion requiring intravenous administration of diuretics (either hospitalized or in an ambulatory basis) in the previous 12 months, e) all the previous criteria were present despite optimal medical management (including use of diuretics, antagonists of the renin-angiotensin-aldosterone system and beta-blockers) and device therapy (including implantable cardioverter defibrillator-ICD and/or cardiac resynchronization therapy-CRT) or attempts to optimize it. Major exclusion criteria were: concurrent inclusion in another study, the presence of left ventricular tract obstruction, uncorrected significant primary valve disease, recent acute coronary syndrome or stroke, hypertrophic or restrictive cardiomyopathy, administration of amrinone, milrinone, enoximone, dopamine or dobutamine in the previous 3 days, administration of levosimendan in the previous 31 days, serum potassium below 3.5mmol/L, estimated glomerular filtration rate <30ml/min/m2 (MDRD-4 formula), systolic blood pressure < 90 mmHg orheart rate > 110 bpm at screening, planned or ongoing evaluation for any of the following procedures: CRT, ICD, coronary revascularization, heart transplant or left ventricular assist device (LVAD) implant, other acute or chronic conditions that would made the patient unsuitable for this study according to the investigator's judgement, anticipated poor compliance and inability or unwillingness to give informed consent.