Use-dependent electrophysiologic effects of amiodarone in coronary artery disease and inducible ventricular tachycardia

Nipavan Chiamvimonvat, L. Brent Mitchell, Anne M. Gillis, D. George Wyse, Robert S. Sheldon, Henry J. Duff

Research output: Contribution to journalArticle

1 Scopus citations

Abstract

Amiodarone produces use-dependent block of cardiac sodium channels in vitro. This study assessed whether similar use-dependent block occurred in 19 patients with coronary artery disease and inducible, sustained, monomorphic ventricular tachycardia treated with amiodarone. Beat-to-beat measurements of ventricular paced QRS durations during 12-beat trains at cycle lengths of 700, 600, 400 and 300 ms were analyzed at a baseline antiarrhythmic drug-free study and after 2 and 10 weeks of amiodarone therapy. At the drug-free study, there were no significant changes in paced QRS durations within the 12-beat trains at any pacing cycle lengths. After 2 and 10 weeks of amiodarone therapy, progressive prolongation of paced QRS durations occurred over the 12-beat trains at pacing cycle lengths of 600, 400 and 300 ms (p < 0.05). Significant changes in QRS duration were not observed at a pacing cycle length of 700 ms. This progressive prolongation in QRS duration can be fitted as a function of beat number to a monoexponential equation and occurred with an onset time constant of 1.02 ± 0.41 beats (306 ± 122 ms) at a pacing cycle length of 300 ms. The magnitude of QRS prolongation increased as the pacing cycle length was shortened. The magnitudes of QRS prolongation were similar after 2 and 10 weeks of amiodarone therapy. In conclusion, use-dependent prolongation in QRS duration occurs at rapid pacing cycle lengths in humans receiving amiodarone.

Original languageEnglish (US)
Pages (from-to)598-604
Number of pages7
JournalThe American journal of cardiology
Volume70
Issue number6
DOIs
StatePublished - Sep 1 1992
Externally publishedYes

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine

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