Quantitative Overview of Randomized Trials of Amiodarone to Prevent Sudden Cardiac Death

Abstract

Background Some randomized clinical trials of amiodarone therapy to prevent sudden cardiac death have had positive results and others have had negative results, but all were relatively small. This meta-analysis aimed to pool all trials to assess the effect of amiodarone on mortality and the impact of differences in patient population and study design on trial outcomes. Methods and Results Fifteen randomized trials were identified, and outcome measures were combined by use of a random effects model. The effect of patient population and study design on total mortality was assessed by use of a hierarchical Bayes model. Amiodarone reduced total mortality by 19% (confidence limits, 6% to 31%; P <.01), with somewhat greater reductions in cardiac mortality (23%, P <.001) and sudden death (30%, P <.001). Mortality reductions were similar in trials enrolling patients after myocardial infarction (21%), with left ventricular dysfunction (22%), and after cardiac arrest (25%). There was a trend toward greater risk reduction in trials requiring evidence of ventricular ectopy (25%) than in the remaining trials (10%). The trials using placebo controls had considerably less risk reduction (10%) than trials with active controls (27%) or usual care controls (42%, posterior odds <0.02). Conclusions Amiodarone reduced total mortality by 10% to 19% in patients at risk of sudden cardiac death. Amiodarone reduced risk similarly in patients after myocardial infarction, with heart failure, or with clinically evident arrhythmia. The apparent inconsistencies among results of randomized trials appear to be due to small sample sizes and the type of control group used, not the type of patient enrolled.