RNLS and heart failure: Hypothesizing that renalase may reflect sympathetic activity, thus exerting cytokine properties, the aims of the study were to determine firstly whether renalase and brain natriuretic peptide (BNP) concentration could be used to differentiate heart failure patients stratified to the category of the ejection fraction and secondly whether plasma renalase could be used as a biomarker for left ventricle hypertrophy in all subgroups of heart failure patients.