REN and hydrops fetalis: In both conditions, there is an autonomic imbalance with increase in sympathetic and renin–angiotensin–aldosterone system activity and withdrawal of parasympathetic efferent activity.29 However, unlike the dramatic improvement in outcomes seen with the use of blockers of the sympathetic and renin–angiotensin–aldosterone system in patients with HFrEF, beta‐blockers and angiotensin‐converting enzyme inhibitors have not been demonstrated in patients with HFpEF or HFmrEF, and ARBs and ARAs have only a modest effect on HF hospitalization.