FACTORS INVOLVED IN THE PRODUCTION OF PAROXYSMAL VENTRICULAR TACHYCARDIA INDUCED BY EPINEPHRINE

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Abstract
Various factors involved in the paroxysmal ventricular tachycardia induced by epinephrine were studied in the dog. Bilateral vagotomy during a paroxysm of ventricular tachycardia stopped this tachycardia within a few beats in all animals. Neither epinephrine nor vagal stimulation alone are capable of inducing paroxysmal ventricular tachycardia in the vagotomized animal. Peripheral vagal stimulation or acetylcholine may produce ventricular tachycardia after the injn. of epinephrine. Maintenance of constant pressure after the injn. of epinephrine by the use of a pressure equalizer prevents the occurrence of ectopic rhythms. A sudden rise in pressure during this period precipiates ventricular tachycardia. A rise in pressure without the injn. of epinephrine does not produce ventricular tachycardia. It is concluded that 2 factors are involved in the epinephrine-induced ventricular tachycardia: a) hyperexcitability of the idioventricular pacemakers due to the presence of epinephrine-stretching of the myocardium due to the sudden increase in pressure may contribute to this effect; b) inhibition of the higher pacemakers through vagal stimulation.

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