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(Circulation Research. 2001;89:807.)
© 2001 American Heart Association, Inc.

Integrative Physiology

Electrical Properties and Conduction in Reperfused Papillary Muscle

Wayne E. Cascio, Hua Yang, Timothy A. Johnson, Barbara J. Muller-Borer, John J. Lemasters

From the Departments of Medicine (W.E.C., H.Y., T.A.J., B.J.M.-B.) and Cell and Developmental Biology (J.J.L.), The University of North Carolina at Chapel Hill, Chapel Hill, NC.

Correspondence to Wayne E. Cascio, MD, University of North Carolina School of Medicine, Division of Cardiology, CB No. 7075, 349 Burnett-Womack Bldg, Chapel Hill, NC 27599-7075. E-mail wcascio{at}med.unc.edu

The reversibility of ischemia-induced changes of extracellular K⁺ concentration ([K⁺]_o), resting membrane potential (E_M), and passive cable-like properties, ie, extracellular resistance and cell-to-cell electrical coupling, and their relationship to recovery of conduction and contraction is described in 25 reperfused rabbit papillary muscles. No-flow ischemia caused extracellular K⁺ accumulation, depolarization of E_M, an increase in whole-tissue (r_t), external (r_o), and internal (r_i) longitudinal resistances, and failure of conduction and contraction. Muscles were reperfused 10 minutes after the onset of ischemia related cell-to-cell electrical uncoupling, ie, 26±1 minutes after arrest of perfusion. In 11 muscles, incomplete reflow occurred with only partial recovery of [K⁺]_o and r_t. In the remaining 14 muscles, reperfusion caused a rapid and parallel decrease in [K⁺]_o, r_t, and r_o. When complete tissue reperfusion occurred, cell-to-cell electrical uncoupling was largely reversible. Thus, cell-to-cell electrical uncoupling did not indicate irreversible injury. Reperfusion induced a depolarizing current widening the difference between the K⁺ equilibrium potential and the E_M. This difference decreased after longer periods of reperfusion. Conduction was restored and conduction velocity approached preischemic values as cell-to-cell electrical interaction was reestablished and E_M recovered. The recovery of r_o preceded r_i, decreasing the ratio of the extracellular to intracellular resistance early in reperfusion, an effect predicted to influence the amplitude of the extracellular voltage field and electrocardiographic ST segments during reperfusion.

Key Words: ischemia • cable-like properties • cell-to-cell electrical coupling • extracellular potassium • conduction

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