Amiodarone-associated proarrhythmic effects. A review with special reference to torsade de pointes tachycardia.

PURPOSE: To assess the incidence of amiodarone-mediated aggravation of ventricular tachyarrhythmias or the development of new arrhythmias, such as torsade de pointes, in patients with cardiac disease. DATA SOURCES AND STUDY SELECTION: A MEDLINE literature search was done to identify articles published during the last 20 years that presented data on amiodarone-associated proarrhythmic events. The articles were divided into three categories: case reports, uncontrolled retrospective studies, and prospective controlled trials. In addition, articles were identified that examined the effects of amiodarone in patients with previously documented drug-induced torsade de pointes.
RESULTS: 65 English-language case reports dealing with torsade de pointes during amiodarone therapy were found in the literature. In many of these cases, other predisposing factors for the development of torsade de pointes were reported. Seventeen studies each reported data from at least 50 patients who were treated with amiodarone for at least 6 months. Of 2878 patients included in these trials, 57 were reported to have a proarrhythmic event while exposed to the drug (an overall incidence of 2%). Torsade de pointes was observed in one third of these patients (an overall incidence of 0.7%). In seven placebo-controlled trials in which the drug was given as monotherapy, amiodarone was not associated with the development of a proarrhythmic event in any patient. Finally, in three reports, 31 patients with previous drug-mediated torsade de pointes were exposed to amiodarone during short- and long-term therapy. In none of these patients did a recurrent episode of torsade de pointes develop, despite the amiodarone-induced prolongation of the QTc interval, which was equivalent to that observed at the time of torsade de pointes during exposure to previous drugs.
CONCLUSIONS: Amiodarone appears to be associated with a remarkably low frequency of proarrhythmic events and an incidence of torsade de pointes of less than 1.0%. This low arrhythmogenicity and the negligible negative inotropic effect of the compound constitute properties that make amiodarone particularly useful in treating high-risk patients prone to sudden cardiac death. Its potential to reduce this risk is currently being evaluated in several large prospective trials.