Spiral defect chaos with intermittency increases mean termination time

TL;DR

This study investigates how varying parameters in cardiac models influences the transition from spiral defect chaos to stable spiral waves, revealing that intermittency can significantly extend the time before activity terminates, with potential implications for atrial fibrillation.

Contribution

It demonstrates the transition from spiral defect chaos to stable spirals via intermittency and quantifies how this affects termination times in cardiac models.

Findings

Mean termination time increases near stable spiral wave parameters.

Intermittency involves alternating periods of chaos and stability.

Partial domain intermittency can occur with quasi-stable spirals.

Abstract

Cardiac models are examples of excitable systems and can support stable spiral waves. For certain parameter values, however, these spiral waves can become unstable, resulting in spiral defect chaos (SDC), characterized by the continuous creation and annihilation of spiral waves and thought to underlie atrial fibrillation. During SDC, the number of spiral waves fluctuates and eventually drops to zero, marking the termination of activity. In this work, we demonstrate that varying a single parameter allows the system to transition from SDC to a single spiral wave, passing through an intermediate regime of intermittency. In this intermittent dynamics, intervals of SDC are sandwiched between non-SDC intervals during which the number of spiral waves remains small and constant. We quantify this intermittency and show that the mean termination time increases significantly as the control parameter approaches values for which a single spiral wave is stable. In addition, we find that it is also possible to have intermittently present quasi-stable spiral waves in part of the computational domain while the remainder of the domain exhibits SDC. Our results may have implications for clinical atrial fibrillation, which often shows intermittency, switching back-and-forth between fibrillation and normal sinus rhythm.