Newer positive inotropic agents in the treatment of chronic cardiac failure. Current status and future directions.

Heart failure is a serious worldwide health problem of major proportions. For many physicians, digitalis (an inotropic agent of limited proportions) and diuretics have proven the standard of treatment for heart failure. Vasodilators have also gained acceptance in recent years. Nevertheless, many patients remain symptomatic and therefore attention has been given to the development of pharmacological agents with mechanisms of action targeted to cardiac and vascular smooth muscle. The newer generation of inotropic agents have clearly been shown to improve the pumping function of the failing heart in patients who remain symptomatic despite digitalis, diuretics and vasodilators, while myocardial oxygen consumption is not enhanced. Several uncontrolled trials with the phosphodiesterase inhibitors enoximone, milrinone and piroximone have concluded that these agents improve exercise capacity and thereby hold promise to enhance quality of life. Large scale controlled trials currently in progress will determine the ultimate efficacy, as well as safety, of these agents. Results to date with several orally active beta-adrenoceptor agonists suggest that their efficacy may be limited by the induction of ventricular arrhythmias.