Effect of amiodarone on dispersion of ventricular repolarization in a canine congestive heart failure model

The effects of amiodarone on ventricular electrophysiological parameters, especially the dispersion of ventricular repolarization, were investigated in a canine model of congestive heart failure (CHF). Dogs were randomized to either a control, amiodarone, CHF, or CHF+amiodarone group. Dogs in the CHF and CHF+amiodarone groups underwent 4-5 weeks of rapid ventricular pacing; dogs in the control and amiodarone groups underwent sham operation only. Amiodarone (20 mg/kg per day) was administered orally, beginning on postoperative Day 1, in the treatment groups; ventricular electrophysiological variables were evaluated 4-5 weeks after rapid pacing or sham operation. In CHF dogs, the transmural dispersion ventricular repolarization time (TDVRT) increased significantly. Amiodarone significantly decreased the TDVRT in CHF dogs. The ventricular fibrillation threshold (VFT) decreased in the CHF group. Amiodarone increased the VFT in CHF dogs. The TDVRT increased in CHF dogs, but amiodarone decreased TDVRT and increased VFT in these dogs. These results suggest a beneficial effect of amiodarone on malignant arrhythmias and may provide the basis for its use in CHF patients.