Dynamics of sustained reentry in a loop model with discrete gap junction resistances

Area of Science:

• Cardiac Electrophysiology
• Computational Biology
• Nonlinear Dynamics

Background:

• Reentry is a key mechanism for cardiac arrhythmias.
• Understanding factors influencing reentry dynamics is crucial for developing antiarrhythmic strategies.
• Intercellular coupling, modeled by gap junction resistance, significantly impacts cardiac electrical propagation.

Purpose of the Study:

• To investigate the effects of discrete intercellular gap junction resistance on cardiac reentry dynamics.
• To characterize the transition from periodic to quasiperiodic reentry in a 1D cardiac cell model.
• To determine how gap junction resistance influences the critical and minimum loop lengths for quasiperiodic reentry.

Main Methods:

• A one-dimensional loop model of cardiac cells was used.
• Each cell was represented by a continuous cable with a modified Beauer-Reuter ionic current formulation.
• Discrete intercellular gap junction resistance (R) was systematically varied.
• The restitution curve, plotting action potential duration against diastolic interval, was analyzed.

Main Results:

• For gap junction resistance below a critical value, propagation transitioned from period-1 to quasiperiodic (QP) reentry at a critical loop length (L(crit)).
• Both L(crit) and the minimum loop length (L(min)) for QP reentry decreased as gap junction resistance (R) increased.
• The bifurcation to QP reentry could be predicted by the slope of the restitution curve, though its shape varied with R.
• Despite variations in R, only two QP modes of propagation were observed, similar to continuous cable models.

Conclusions:

• Discrete gap junction resistance significantly influences the initiation and extent of quasiperiodic reentry in cardiac tissue models.
• The findings highlight the complex interplay between cellular properties, intercellular coupling, and reentry dynamics.
• Further research into the impact of heterogeneous gap junction resistance may provide deeper insights into arrhythmia mechanisms.