Quinapril in chronic heart failure. Angiotensin converting enzyme inhibitors are now firmly established in the treatment of patients with chronic heart failure (CHF). Their beneficial acute and chronic hemodynamic effects are not associated with reflex tachycardia or drug tolerance. Angiotensin converting enzyme inhibitors produce symptomatic improvement and improve exercise capacity in all grades of heart failure. They also improve the prognosis of patients with severe heart failure. Quinapril is a recently introduced, nonsulfhydryl ACE inhibitor, whose intermediate half-life makes it well-suited for the treatment of patients with CHF. The acute and chronic hemodynamic effects of quinapril are similar to those of other ACE inhibitors. In a large, multicenter, randomized, placebo-controlled study of 225 patients with mild to moderate CHF, 10 to 40 mg/day quinapril significantly improved clinical status and exercise capacity in a dose-related manner. The incidence of side effects did not differ significantly from that of placebo. The initial studies with quinapril are promising and warrant further clinical investigation of this compound. 