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Electrical properties and conduction in reperfused papillary muscle
W E Cascio1, H Yang, T A Johnson
1Department of Medicine, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7075, USA. wcascio@med.unc.edu
Circulation Research
|October 27, 2001
Summary
Reperfusion reversed ischemia-induced changes in extracellular K(+), membrane potential, and electrical coupling, restoring conduction and contraction. Cell-to-cell uncoupling was reversible, indicating it does not signify irreversible injury.
Area of Science:
- Cardiovascular Physiology
- Electrophysiology
- Ischemia-Reperfusion Injury
Background:
- Ischemia leads to extracellular K(+) accumulation, membrane depolarization, and impaired electrical properties, affecting cardiac function.
- Understanding the reversibility of these changes during reperfusion is crucial for predicting recovery of conduction and contraction.
Purpose of the Study:
- To investigate the reversibility of ischemia-induced changes in extracellular K(+) concentration, resting membrane potential, and passive electrical properties.
- To determine the relationship between the recovery of these parameters and the restoration of conduction and contraction during reperfusion.
Main Methods:
- 25 rabbit papillary muscles were subjected to no-flow ischemia followed by reperfusion.
- Measurements included extracellular K(+) concentration ([K(+)](o)), resting membrane potential (E(M)), and tissue resistances (r(t), r(o), r(i)).
- Cell-to-cell electrical coupling and conduction were assessed.
Main Results:
- Ischemia caused [K(+)](o) accumulation, E(M) depolarization, increased resistances, and loss of conduction/contraction.
- Reperfusion led to a parallel decrease in [K(+)](o), r(t), and r(o) with complete reflow.
- Cell-to-cell electrical uncoupling was largely reversible upon reperfusion, indicating it is not indicative of irreversible injury.
- Conduction and contraction recovery correlated with reestablished electrical coupling and E(M) recovery.
- Recovery of extracellular resistance (r(o)) preceded intracellular resistance (r(i)) recovery.
Conclusions:
- Cell-to-cell electrical uncoupling during ischemia is a reversible phenomenon and does not indicate irreversible injury.
- Recovery of electrical properties and conduction during reperfusion is dependent on the reversal of [K(+)](o) accumulation and restoration of membrane potential.
- The differential recovery of extracellular and intracellular resistance during reperfusion may influence extracellular voltage fields and ECG ST segments.