Digitalis--friend or foe?

Abstract

The therapeutic efficacy of cardiac glycosides is not widely appreciated either in respect of their positive inotropic value or antiarrhythmic activity. Although cardiac glycosides do not prevent an increase in ventricular rates during exercise they do slow the heart rate at rest in patients with atrial fibrillation. The clinical importance of the potentially beneficial influence of the digitalis glycosides on the negative force-frequency relationship (Bowditch effect), preload-force relationship (Frank-Starling's Law) and baroreceptor dysfunction in heart failure await clarification. In patients with heart failure, the positive inotropic effects of the digitalis glycosides are mild, but show no tolerance during prolonged administration. Digitalis glycosides are the only group of positive inotropic drugs that persistently increase the ejection fraction during long-term administration in patients with heart failure. These haemodynamic benefits are translated into decreased symptoms and increased exercise capacity in patients with congestive heart failure. Although their clinical efficacy in the different stages of heart failure remains undefined, recent evidence indicates that their therapeutic benefit is on a par with diuretics and ACE inhibitors in symptomatic heart failure. Results of studies specifically directed to determining the impact of the cardiac glycosides on prognosis are awaited.