A simulation of cardiac action currents having curl

Area of Science:

• Computational electrophysiology
• Biophysics
• Cardiac modeling

Background:

• Cardiac tissue exhibits complex electrical properties influencing action potential propagation.
• Anisotropic electrical conductivity is a key feature of cardiac tissue.
• Previous studies have detected magnetic fields above cardiac tissue, but the underlying mechanisms were not fully elucidated.

Purpose of the Study:

• To investigate the relationship between electrical conductivity asymmetry and magnetic field generation in a simulated cardiac slice.
• To explain the origin of nonzero magnetic fields observed experimentally above cardiac tissue.

Main Methods:

• A two-dimensional digital simulation of cardiac tissue was performed.
• An anisotropic bidomain model was employed, incorporating fast sodium physiology.
• The simulation analyzed current flow patterns under varying degrees of inner and outer electrical conductivity asymmetry.

Main Results:

• A specific current flow pattern with nonzero curl was observed when inner asymmetry exceeded outer asymmetry.
• This current loop involves longitudinal and transverse current components in both intracellular and extracellular domains.
• The simulation successfully explains the generation of a nonzero magnetic field (Bz) above the simulated cardiac tissue.

Conclusions:

• Electrical conductivity asymmetry in cardiac tissue is a direct cause of measurable magnetic fields.
• The anisotropic bidomain model accurately predicts observed magnetic field phenomena.
• This research provides a mechanistic link between cellular electrophysiology and noninvasive magnetic field detection in the heart.