Haemodynamic, hormonal, and electrolyte responses to captopril in resistant heart failure.

In five patients with resistant heart failure treated with the oral converting-enzyme inhibitor, captopril, standardised and intensive haemodynamic, hormone, and electrolyte monitoring showed significantly raised cardiac output and reduced arterial, pulmonary-wedge, and pulmonary-artery pressures which correlated closely with concomitant alterations in the activity of the renin-angiotensin system. These changes occurred in the absence of a natriuresis or diuresis. Clinical improvement was dramatic and paralleled the objective haemodynamic changes. Hyponatraemia and a rise in plasma-potassium were noted. Captopril is a major advance in the treatment of resistant heart failure, and its beneficial haemodynamic effects relate primarily to a blockade of the renin-angiotensin system, the activity of which is increased by conventional drug therapy.