Major treatment advances have been made in recent years, and renin–angiotensin–aldosterone system inhibitors (RAASis), including angiotensin-converting enzyme inhibitors (ACEis), angiotensin II receptor blockers (ARBs), and mineralocorticoid receptor antagonists (MRAs), are guideline-recommended medications for patients with HF that reduce the risk of cardiovascular complications and improve survival. This evidence concerns the gene REN and hydrops fetalis.