The 2021 ESC Guidelines on HF provide a Class I recommendation for the treatment of all HFrEF patients, which is the combination of any of the following drugs: angiotensin-converting enzyme (ACE) inhibitor, or angiotensin receptor-neprilysin inhibitor (ARNI), a beta-blocker, a mineralocorticoid receptor antagonist (MRA), and a sodium-glucose co-transporter 2 (SGLT2) inhibitor (dapagliflozin or\and empagliflozin). The gene discussed is ACE; the disease is hydrops fetalis.