STUDIES ON DIGITALIS. XII. THE EFFECTS OF PAIRED ELECTRICAL STIMULATION ON DIGITALIS-INDUCED ARRHYTHMIAS

¹ Cardiology Branch, National Heart Institute, Bethesda, Maryland

Paired electrical stimulation of the ventricles allows two consecutive refractory periods to occur with each effective contraction, and thus permits a slowing of the effective contraction rate and suppression of a variety of arrhythmias. Twenty-one anesthetized, closed-chest dogs received a ouabain infusion (1 µ/kg/min) until death. Seven of the animals served as controls. In 7 animals in which paired electrical stimulation was begun after the development of a major arrhythmia, the arrhythmias were suppressed until fatal ventricular fibrillation developed. In 7 animals in which paired stimulation was begun prior to the ouabain infusion, the dose of glycoside required to produce arrhythmia was increased, but the fatal dose was reduced. In 14 other dogs, a single large dose of ouabain (70 µg/kg) was given to produce ventricular tachycardia. The survival among animals treated with paired stimulation (8 of 10) and controls (3 of 4) was comparable, hut paired stimulation effectively suppressed the arrhythmia and slowed the heart rate from an average of 226 to 137/min. When paired stimulation was discontinued after 2 to 6 hr, the toxic effects of the glycoside had disappeared or waned. Although paired electrical stimulation is not without hazard, the technique may prove useful in the clinical management of digitalis intoxication.