Pulsed low-energy stimulation initiates electric turbulence in cardiac tissue

Abstract

Interruptions in nonlinear wave propagation, commonly referred to as wave breaks, are typical of many complex excitable systems. In the heart they lead to lethal rhythm disorders, the so-called arrhythmias, which are one of the main causes of sudden death in the industrialized world. Progress in the treatment and therapy of cardiac arrhythmias requires a detailed understanding of the triggers and dynamics of these wave breaks. In particular, two very important questions are: 1) What determines the potential of a wave break to initiate re-entry? and 2) How do these breaks evolve such that the system is able to maintain spatiotemporally chaotic electrical activity? Here we approach these questions numerically using optogenetics in an in silico model of human atrial tissue that has undergone chronic atrial fibrillation (cAF) remodelling. In the lesser studied sub-threshold illumination régime, we discover a new mechanism of wave break initiation in cardiac tissue that occurs for gentle slopes of the restitution characteristics. This mechanism involves the creation of conduction blocks through a combination of wavefront-waveback interaction, reshaping of the wave profile and heterogeneous recovery from the excitation of the spatially extended medium, leading to the creation of re-excitable windows for sustained re-entry. This finding is an important contribution to cardiac arrhythmia research as it identifies scenarios in which low-energy perturbations to cardiac rhythm can be potentially life-threatening.

Optoelectronic control of cardiac rhythm: Toward shock‐free ambulatory cardioversion of atrial fibrillation

“…If these findings hold true for large AF animal models and AF patients, such a strategy could reduce the energy consumption required for optogenetic AF termination. However, care should be taken not to promote arrhythmias via such light pulses of low intensity [55].…”

Atrial fibrillation: Insights from animal models, computational modeling, and clinical studies

“… 19 Therefore, according to the “mother rotor” hypothesis, wavebreaks are the hallmark of AF maintenance as they lead to further rotor initiation and fibrillatory waves. 20 Optical mapping and computational simulation studies of the atria have revealed rapid rotors activating atrial tissue at high-frequency and driving the fibrillatory conduction with a degree of spatiotemporal organization during the apparent chaos. 13 , 18 , 21 …”