Arrhythmogenicity of dopamine, dobutamine, and epinephrine in thiamylal-halothane anesthetized dogs

The arrhythmogenicity of epinephrine, dopamine, and dobutamine, administered by constant-rate infusion, was determined in vagotomized and nonvagotomized thiamylal-halothane anesthetized dogs. Electrocardiograms and atrioventricular bundle electrograms revealed the development of atrial, junctional, and ventricular arrhythmias. The 3 drugs produced atrial arrhythmias at dosages smaller than those required to produce ventricular arrhythmias. The mean dosages (microgram/kg-1/min-1) required to produce ventricular arrhythmias on duplicate trials in vagotomized dogs were for epinephrine, 0.6 +/- 0.2; dopamine, 22.8 +/- 14.8; and dobutamine, 11.6 +/- 5.2. The corresponding doses for nonvagotomized dogs were for epinephrine, 0.8 +/- 0.3; dopamine, 35.3 +/- 13.5; and dobutamine, 21.9 +/- 13.9. Most ventricular arrhythmias originated from a single focus in the left ventricle. Heart rate and blood pressure were significantly increased immediately before ventricular arrhythmia appeared. We conclude that epinephrine, dopamine, and dobutamine are capable of producing cardiac arrhythmias in vagotomized and nonvagotomized thiamylal-halothane anesthetized dogs and that bilateral vagotomy decreases the dosage of epinephrine, dopamine, and dobutamine required to produce cardiac arrhythmias.