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Ephaptic coupling and the source-sink effect of cardiac conduction
Jingwu Pan1, Peter Hanna1, Alan Garfinkel1
1Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.
The Journal of Physiology
|March 26, 2026
Summary
Ephaptic coupling, unlike gap junction coupling, does not require a critical number of cells for cardiac conduction, eliminating the source-sink effect. The interaction between ephaptic and gap junction coupling influences conduction and may impact heart rhythm disorders.
Area of Science:
- Cardiovascular Physiology
- Computational Biology
- Biophysics
Background:
- Cardiac electrical conduction relies primarily on gap junction coupling, involving a 'source-sink effect' where a minimum number of excited cells are needed.
- The influence of ephaptic coupling (electrical field effects) on this source-sink effect in cardiac tissue remains largely unexplored.
Purpose of the Study:
- To investigate the impact of ephaptic coupling, both independently and in conjunction with gap junction coupling, on the cardiac source-sink effect.
- To analyze how different depolarization triggers (external stimulation, delayed afterdepolarization, automaticity) interact with ephaptic and gap junction coupling.
Main Methods:
- Computer simulations using a one-dimensional cardiac myocyte model with a cleft.
- Incorporation of junctional ion channel distributions and varying cleft widths.
- Analysis of conduction triggered by different types of cellular depolarization.
Main Results:
- Pure ephaptic coupling eliminates the source-sink effect, requiring only one stimulated cell for conduction.
- Increased gap junction conductance elevates the number of cells needed for conduction, consistent with the source-sink theory.
- Complex dependencies of the source-sink effect on cleft width arise from ephaptic attenuation of sodium current and enhancement of potassium current.
Conclusions:
- Ephaptic coupling and intercellular cleft width play significant, non-trivial roles in cardiac conduction dynamics and the source-sink effect.
- These findings suggest that altered gap junctions and cleft structures in disease states could impact arrhythmogenesis through modified ephaptic interactions.
Keywords:
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