Cardiac strength-interval curves calculated using a bidomain tissue with a parsimonious ionic current

Area of Science:

• Cardiac Electrophysiology
• Computational Biology
• Biophysics

Background:

• The strength-interval curve is crucial for understanding cardiac tissue response to electrical stimuli.
• Previous models, like Beeler-Reuter and Luo-Rudy, are complex, hindering interpretation.
• A need exists for simpler, yet accurate, models of cardiac electrophysiology.

Purpose of the Study:

• To investigate cardiac tissue's strength-interval relationship using a parsimonious ionic model.
• To reproduce the polarity-dependent dip observed in experimental strength-interval curves.
• To identify the essential ionic and tissue properties responsible for this phenomenon.

Main Methods:

• Utilized a simplified ionic model with two currents: rapid sodium current (INa) and inwardly rectifying potassium current (IK).
• Performed bidomain tissue simulations incorporating this parsimonious model.
• Analyzed model variants to determine necessary conditions for the strength-interval curve characteristics.

Main Results:

• The parsimonious model successfully reproduced the distinctive dip in the anodal strength-interval curve.
• The model accurately simulated experimentally measured action potential waveforms.
• Identified INa, IK, and anisotropic bidomain tissue as critical for the polarity-dependent dip.

Conclusions:

• A simplified ionic model can effectively capture complex cardiac electrophysiological behaviors like the strength-interval curve.
• The study elucidates the minimal physiological requirements for the anodal strength-interval dip.
• This parsimonious approach facilitates more accessible and interpretable cardiac modeling.