The effects of isoproterenol on the cardiac conduction system: Site- specific dose dependence

Sergio F. Cossú, Steven A. Rothman, I. Lisa Chmielewski, Henry H. Hsia, R. Lee Vogel, John M. Miller, Alfred E. Buxton

Research output: Contribution to journalArticle

10 Scopus citations


Introduction: Isoproterenol is used to assess and facilitate AV nodal conduction, and thus potentiate the induction of supraventricular arrhythmias. It is commonly administered in increasing doses until a predetermined decrease in sinus cycle length, usually 20% to 30%, occurs. This regimen may result in undesirable side effects. We have observed that effects of isoproterenol on the AV node may occur prior to achieving the target sinus cycle length. The purpose of this study was to determine whether the sinus and AV nodes have equal sensitivity to isoproterenol. Methods and Results: Thirty-eight consecutive patients, who underwent electrophysiologic evaluation for a variety of indications, were given incremental doses of isoproterenol at 0.007, 0.014, 0.021, and 0.028 μg/kg per minute. Sinus cycle length and AV node function were assessed at baseline and after 5 minutes at each dose. The percent change from baseline in AV node function was compared with the change in sinus cycle length at each dose interval. Significantly greater decreases were observed in the anterograde and retrograde AV nodal Wenckebach cycle length (P < 0.0001) than in the sinus cycle length at the lowest isoproterenol dose (0.007 μg/kg per min). These differences were not apparent at higher doses. A sustained supraventricular tachycardia was inducible in 15 of 38 patients in the presence of isoproterenol, of which 40% occurred at the lowest dose. Conclusions: The AV node is more sensitive than the sinus node to the effects of isoproterenol. Lower doses of isoproterenol than those commonly used may often facilitate the induction of a supraventricular tachyarrhythmia, thus reducing side effects.

Original languageEnglish (US)
Pages (from-to)847-853
Number of pages7
JournalJournal of Cardiovascular Electrophysiology
Issue number8
StatePublished - Jan 1 1997
Externally publishedYes


  • Atrioventricular conduction
  • Electrophysiologic study
  • Isoproterenol
  • Refractoriness
  • Supraventricular tachycardia

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)

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