What is the role of MRA therapy (spironolactone or eplerenone) in HFrEF and what is a major electrolyte concern?

• A. They reduce mortality and hospitalization; monitor potassium and creatinine for hyperkalemia.
• B. They increase ejection fraction by direct inotropic action.
• C. They are only used in HFpEF.
• D. They replace diuretics as the main therapy.

Answer: (A)

In HFrEF, spironolactone or eplerenone work by blocking aldosterone, which reduces sodium retention, limits fibrosis, and improves outcomes. They have been shown to lower mortality and reduce hospitalizations when added to guideline-directed therapies. The main electrolyte concern is hyperkalemia, because aldosterone blockade decreases potassium excretion in the kidneys. The risk rises with kidney dysfunction or with other meds that raise potassium (like ACE inhibitors/ARBs) or potassium supplements. So after starting or dose-adjusting an MRA, check potassium and creatinine soon after and monitor regularly going forward.