Electrical properties and conduction in reperfused papillary muscle

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.