Role of angiotensin-converting enzyme inhibitors in congestive heart failure. Conventional therapy for congestive heart failure (CHF) includes sodium-restricted diet, diuretics, digitalis, vasodilators, and short-term intravenous administration of beta-adrenergic agonists during episodes of decompensation. A specific class of vasodilators, the angiotensin-converting enzyme inhibitors, has recently gained predominance in the treatment of congestive heart failure. The primary mechanism of action is to reduce production of angiotensin II by competitive inhibition of the enzyme that converts angiotensin I into angiotensin II. Reduced levels of angiotensin II, in turn, promote vasodilation and lower aldosterone production. The benefits of angiotensin-converting enzyme inhibitor therapy in chronic congestive heart failure have been demonstrated by improvement in left ventricular performance, exercise capacity, functional status (using New York Heart Association classification), and survival. 