Study of cardiac pacemaker excitation using generic ionic models and realistic cell distribution
Adrian D Bradd1, Amr Al Abed, Tianruo Guo
1Graduate School of Biomedical Engineering, University of New South Wales, Sydney 2052, Australia.
Summary
Investigating cardiac action potentials (APs) in rabbit sinoatrial node (SAN) models revealed that a mosaic architecture, not a gradient one, supports spontaneous excitation without peripheral SAN cells.
Area of Science:
- Computational Biology
- Cardiac Electrophysiology
- Mathematical Modeling
Background:
- The sinoatrial node (SAN) is the heart's natural pacemaker, initiating cardiac action potentials (APs).
- Understanding SAN architecture is crucial for comprehending cardiac rhythm regulation.
- Two proposed models for SAN function are the gradient and mosaic hypotheses.
Purpose of the Study:
- To implement and compare generic ionic models in a realistic 2D rabbit SAN geometry.
- To investigate the functional implications of gradient versus mosaic SAN architecture hypotheses.
- To assess the role of peripheral SAN cells in cardiac excitation initiation.
Main Methods:
- Development of a realistic 2D computational model of rabbit SAN geometry.
- Implementation of generic ionic models optimized to experimental cardiac action potentials (APs).
- Simulation and analysis of AP propagation under gradient and mosaic architectural assumptions.
Main Results:
- A simplified gradient SAN model indicated the peripheral region is essential for AP initiation and propagation.
- Optimized single-cell parameters did not accurately reproduce experimental APs in the 2D rabbit geometry.
- An adapted mosaic SAN geometry model demonstrated that peripheral SAN cells are not required for spontaneous excitation.
Conclusions:
- The mosaic hypothesis provides a more accurate representation of SAN function regarding spontaneous excitation.
- Peripheral SAN cells may not be essential for initiating regular cardiac rhythm in this model.
- Computational modeling aids in elucidating complex cardiac electrophysiology and SAN architecture.
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