REN and heart failure: RCT: Randomised control trial; BP: Blood pressure; 6MWT: six minute walk test; HF: Heart failure; CVD: Cardiovascular disease; MCS: Mechanical circulatory support; PTH: Parathyroid hormones; BNP: Brain natriuretic peptide; hsCRP: High-sensitivity C-reactive protein; LV: left ventricle; EF: Ejection fraction; PRA: Plasma renin activity.