ACE and congestive heart failure: Activation of the renin-angiotensin-aldosterone system (RAAS) plays a pivotal role in cardiovascular disease and treatment with angiotensin-converting enzyme inhibitors (ACEIs), which inhibit the hydrolytic conversion of angiotensin I (ATI) to angiotensin II (ATII), forms an important part of the treatment for congestive heart failure (CHF), hypertension, and ischemic heart disease.