Effects of ventricular stimulation and potassium administration on digitalis-induced arrhythmias

Paired electrical ventricular pacing has been shown to be an effective means of overcoming digitalis-induced arrhythmias, but it has not been used clinically because of the danger of inducing ventricular fibrillation and because the second contraction interferes with ventricular filling. For these reasons, the possibility that ventricular pacing with a single electrical stimulus might accomplish the same effect was examined. A pacing catheter was passed by way of the jugular vein into the right ventricle of 16 dogs, and ouabain was infused at the rate of 1 μg/kg per min. In 9 control animals serious ventricular arrhythmias occurred at 51.0 ± 3.6 (SEM) min and death at 94.9 ± 5.9 min. In 7 dogs arrhythmias occurred at 51.6 ± 3.7 min but were completely abolished by pacing at a frequency 20 percent above the intrinsic rate. However, the total cumulative dose of ouabain that caused death remained unchanged, and the animals with pacing died of ventricular fibrillation at 94.6 ± 8.2 min. In other studies in 23 dogs infusion of potassium was started at the time of initial toxicity, but it had no effect on the cumulative dose of ouabain considered lethal. Neither pacing nor infusion of potassium altered the maximal tolerated dose of ouabain. We found that arrhythmias can be completely suppressed by ventricular pacing, but that they recur during administration of potassium. We conclude that ventricular pacing with a single electrical stimulus will effectively overcome serious digitalis-induced arrhythmias and that it should be considered for trial in patients with refractory digitalis toxicity.