REN and heart failure: Current heart failure guidelines [76] recommend the administration of four main classes of medications: (1) renin–angiotensin system inhibitors (angiotensin receptor-neprilysin inhibitors (ARNi), angiotensin-converting enzyme inhibitors (ACEi), or angiotensin II receptor blockers (ARB)); (2) beta-blockers; (3) mineralocorticoid receptor antagonists (MRAs); and (4) sodium-glucose cotransporter-2 inhibitors (SGLT2i).