REN and hydrops fetalis: We do however acknowledge that several other, important bioactive molecules will be therapeutically relevant for the treatment of HF in the elderly; however these have been reviewed in detail elsewhere (for example TGF-β signalling [138], [139] and renin–angiotensin–aldosterone (RAAS)/natriuretic peptide systems [140], [141], [142], and are therefore not considered in detail here).