Author + information
- Received August 20, 1984
- Revision received October 30, 1984
- Accepted November 15, 1984
- Published online May 1, 1985.
- ↵1Address for reprints: Steven M. Yabek, MD, Department of Pediatrics, University of New Mexico, School of Medicine, Albuquerque, New Mexico 87131.
The acute cellular electrophysiologic actions of amio-darone on isolated neonatal and adult canine ventricular muscle and Purkinje fibers were evaluated using standard microelectrode techniques. Amiodarone, 10−5to 5 × 10−5M(0.68 to 34 μ/ml), significantly (p < 0.05) prolonged adult ventricular muscle action potential duration and voltage-dependent refractoriness at all concentrations, thereby demonstrating typical class III antiarrhythmic effects. Similar concentrations had no significant effects on neonatal ventricular muscle. Amio-darone significantly shortenedaction potential duration and refractoriness of both neonatal and adult Purkinje fibers, with neonatal fibers having a greater sensitivity to the drug. At the standard stimulation rate of 1 Hz, amiodarone had no effects on action potential amplitude or maximal rate of rise of phase 0 of the action potential (Vmax) of any tissues. At faster stimulation frequencies (2 to 4 Hz), amiodarone produced frequency-dependent decreases in action potential amplitude and Vmaxof all neonatal and adult preparations.
The data indicate that amiodarone exhibits a complex aggregate of electrophysiologic actions that include significant frequency-related class I effects. Compared with adult myocardium, neonatal tissues demonstrated altered responsiveness to amiodarone, a feature common to many antiarrhythmic compounds.
- Received August 20, 1984.
- Revision received October 30, 1984.
- Accepted November 15, 1984.
- American College of Cardiology Foundation