Effects of intravenous anesthetics, thiopental, fentanyl, and morphine on ventricular delayed activation in a canine myocardial infarction model.

We examined the effects of intravenous anesthetics (thiopental, fentanyl and morphine) on the ventricular activation in a canine myocardial infarction model. Thiopental at 5 and 10 mg/kg delayed or abolished the delayed activation in the infarcted zones with slight delay of activation of the normal zones. Fentanyl at 30 micrograms/kg slightly but significantly prolonged the activation time in both normal and infarcted zones. Morphine at 1 mg/kg did not produce any significant effect. Thiopental, but neither fentanyl nor morphine, inhibited ventricular stimulation-induced arrhythmias. Thus, thiopental, but not fentanyl nor morphine, markedly depressed the delayed activation in myocardial infarction, which may affect and probably inhibits the ventricular arrhythmias in myocardial infarction. It also should be kept in mind that thiopental may have arrhythmogenic effects in myocardial infarction.