Amiodarone in long term prophylaxis.

Amiodarone is predominantly a potassium channel inhibitor which prolongs repolarisation and refractoriness, and thus qualifies as a Group III antiarrhythmic agent. In addition, it possesses a variety of electrophysiological actions such as sodium channel blockade, calcium channel blockade and noncompetitive inhibition of adrenergic receptors. In the studies reported below, the incidence of successful treatment of refractory ventricular arrhythmias with amiodarone appears to range between 50 to 60% in the first year. However, there are very few prospective randomised studies which assess its efficacy in controlling ventricular tachycardia in comparison with placebo or another antiarrhythmic compound. As there have been no controlled studies to examine the impact of amiodarone in preventing ventricular tachycardia in survivors of cardiac arrest compared with either no treatment or with alternative therapies, the actual efficacy of amiodarone in patients who have survived a cardiac arrest is virtually unknown. Although there are indications that amiodarone reduces the incidence of sudden death in patients with malignant arrhythmias, definitive evidence based on controlled trials is not available.