Active Modulation of Electrical Coupling between Cardiac Cells of the Dog: A Mechanism For Transient and Steady State Variations in Conduction Velocity

Propagation velocities of action potentials were measured simultaneously along the longitudinal and transverse axes of cardiac fibers in ventricular muscle. The anisotropic distribution of propagation velocities was found to be altered transiently and in the steady state by the rate and pattern of s...

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Bibliographic Details
Published in:Circulation research 1982-09, Vol.51 (3), p.347-362
Main Authors: Spach, Madison S, Kootsey, J Mailen, Sloan, Joseph D
Format: Article
Language:English
Subjects:
action potential
Action Potentials - drug effects
Animals
cardiac muscle
Cell Communication
Dogs
Electric Stimulation
Electrophysiology
Heart Conduction System - physiology
Heart Ventricles - innervation
Models, Biological
Ouabain - pharmacology
Papillary Muscles - innervation
Papillary Muscles - physiology
Ventricular Function
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Summary:Propagation velocities of action potentials were measured simultaneously along the longitudinal and transverse axes of cardiac fibers in ventricular muscle. The anisotropic distribution of propagation velocities was found to be altered transiently and in the steady state by the rate and pattern of stimulation and by ouabain. The relative amount of velocity change varied with the direction of propagation and was greatest in the direction perpendicular to the long fiber axis. None of the variables usually associated with the membrane ionic mechanism of depolarization—resting potential, Vmax, and Tfoot—showed enough variation to account for the observed changes in velocity. A simplified anisotropic propagation model representing the internal current pathway as an alternating sequence of cytoplasmic and junctional resistance is presented, taking into account the larger contribution to the internal resistance made by the cell couplings in the transverse direction than in the longitudinal direction. On the basis of this model, it was concluded that the observed changes in velocity were due to changes in cell coupling. Both transient and steady state velocity changes were found to correspond to changes in the action potential duration, suggesting that there is a common factor, such as the internal calcium and/or sodium concentrations, linking the control of the action potential duration and the coupling resistance between cardiac cells.
ISSN:0009-7330
1524-4571
DOI:10.1161/01.RES.51.3.347