ACE and congestive heart failure: The unique importance of MRAs in CHF management is thought to be related to mitigation of aldosterone breakthrough (ABT), [4] a phenomenon wherein individuals treated with renin-angiotensin-aldosterone system (RAAS) modulating drugs, such as angiotensin converting enzyme inhibitors (ACE-I) or angiotensin receptor blockers (ARB), exhibit an increase in plasma aldosterone concentration following treatment [5].