Current flow patterns in two-dimensional anisotropic bisyncytia with normal and extreme conductivities

Area of Science:

• Biophysics
• Computational Biology
• Cardiovascular Physiology

Background:

• Cardiac tissue functions as an electrical syncytium in both intracellular and extracellular spaces.
• Anisotropic conductivity, differing along and across fiber directions, is characteristic of cardiac tissue.
• Previous models often assume isotropic conductivity, potentially oversimplifying electrical behavior.

Purpose of the Study:

• To analyze two-dimensional anisotropic cardiac tissue using integral equations.
• To develop a numerical model for realistic cardiac tissue based on mathematical results.
• To investigate the impact of anisotropic conductivity on electrical potentials and currents.

Main Methods:

• Developed integral equations for intracellular and extracellular potentials, longitudinal currents, and membrane currents.
• Created a numerical model for idealized two-dimensional cardiac tissue.
• Performed computer simulations with normal and reciprocal conductivity patterns, using circular isochrones for transmembrane voltage.

Main Results:

• Anisotropic conductivity significantly alters current flow patterns, creating large loops in resting tissue with reciprocal conductivity ratios.
• Current paths can involve multiple transmembrane excursions (four or more) under anisotropic conditions, unlike the typical two in isotropic models.
• Normal conductivity patterns show predominantly local currents with two transmembrane passages, but anisotropic bisyncytia exhibit distinct properties from 1D strands.

Conclusions:

• Anisotropic conductivity has profound qualitative and quantitative effects on cardiac electrical activity.
• The assumption of isotropic conductivity can lead to inaccurate representations of cardiac electrical behavior.
• This model provides insights into complex current flow in realistic, anisotropic cardiac tissue.