Amiodarone versus bretylium for suppression of reperfusion arrhythmias in dogs

Reperfusion arrhythmias are an important complication of interventions to limit infarct size. Recently, amiodarone has been shown to be rapidly effective in suppressing sustained, incessant ventricular tachycardia and ventricular fibrillation in this setting. This study evaluated the time course of arrhythmia suppression and comparative efficacy of amiodarone versus bretylium in a canine model of reperfusion arrhythmias. Of 23 dogs subjected to a Harris two-stage coronary artery ligation followed by release, 18 demonstrated clinically significant ventricular arrhythmias and received either intravenous amiodarone, 5 mg/kg (9 dogs), or intravenous bretylium, 5 mg/kg (9 dogs). Direct-current shocks for sustained ventricular tachycardia or ventricular fibrillation were administered as necessary. Amiodarone rapidly suppressed sustained ventricular tachycardia and ventricular fibrillation in this model with no dog in the amiodarone-treated group requiring cardioversion after completion of the 15-minute infusion versus 4 of 9 dogs in the bretylium-treated group (p less than 0.05). Amiodarone was more effective than bretylium in suppressing episodes of sustained ventricular tachycardia/ventricular fibrillation, episodes of nonsustained ventricular tachycardia, and premature ventricular complexes. The blood pressure and heart rate decreased more after amiodarone administration than after bretylium administration. We conclude that, in the canine reperfusion arrhythmia model, amiodarone is rapidly effective in suppressing ventricular arrhythmias and is more effective than bretylium.