Circulatory basis for the use of angiotensin converting enzyme inhibitors in hypertension and cardiac failure.

The renin-angiotensin system has a range of physiological actions concerned with the control of the circulation. Angiotensin II has both an immediate and a delayed pressor effect; it stimulates the secretion of aldosterone and antidiuretic hormone, promotes thirst, stimulates the sympathetic nervous system at various sites while inhibiting vagal tone, and has a range of direct effects on the kidney. Several aspects of this range of actions can become deranged in a number of forms of hypertension as well as in congestive cardiac failure. Hence much effort has been directed in recent years to the development of agents designed to interfere with the renin-angiotensin system and to apply these clinically in the treatment of hypertension and congestive cardiac failure. Orally active converting enzyme inhibitors are of proven benefit not only in renovascular hypertension, but also, when combined with loop diuretics, in the treatment of intractable hypertension as well as, both alone and in combination with thiazide diuretics, in the treatment of essential hypertension. In congestive cardiac failure controlled trials have shown that converting enzyme inhibitors can improve exercise tolerance while diminishing lassitude, correct potassium deficiency, and limit ventricular arrhythmias. Energetic efforts are being made to develop orally active inhibitors of the enzyme renin itself, since these should be more specific in action than the presently available and very successful converting enzyme inhibitors.