Effects of digitalization and beta-adrenergic blockade on arrhythmias induced by the direct current defibrillator

Summary

The lowest mean electrical energy delivered by a D. C. defibrillator, which could induce ventricular tachycardia was determined in 20 dogs and found to be 132 W/sec. In the same animals, immediately afterwards, acute digitalization was carried out with acetylstrophanthidine and the mean electrical energy required to induce ventricular tachycardia was found to be 76 W/sec. Following acute b-adrenergic blockade with intravenous administration of Trasicor, the electrical energy had to be markedly increased (mean 230 W/sec) in order to induce ventricular tachycardia. On the contrary, acute digitalization during b-adrenergic blockade decreased the incidence of arrhythmiae instead of increasing it. (Maximal electrical energy of 400 W/sec could not induce ventricular tachycardia in all animals). This paradoxical effect of digitalization may be related to a possible b-adrenergic receptor blocking action of acetylstrophanthidine. -B-adrenergic blocking agents were also found to protect the animals as well as the patients from developing post-counter shock ventricular arrhythmiae.