Multiple mechanisms of spiral wave breakup in a model of cardiac electrical activity

Abstract

It has become widely accepted that the most dangerous cardiac arrhythmias are due to reentrant waves, i.e., electrical wave(s) that recirculate repeatedly throughout the tissue at a higher frequency than the waves produced by the heart's natural pacemaker (sinoatrial node). However, the complicated structure of cardiac tissue, as well as the complex ionic currents in the cell, have made it extremely difficult to pinpoint the detailed dynamics of these life-threatening reentrant arrhythmias. A simplified ionic model of the cardiac action potential (AP), which can be fitted to a wide variety of experimentally and numerically obtained mesoscopic characteristics of cardiac tissue such as AP shape and restitution of AP duration and conduction velocity, is used to explain many different mechanisms of spiral wave breakup which in principle can occur in cardiac tissue. Some, but not all, of these mechanisms have been observed before using other models; therefore, the purpose of this paper is to demonstrate them using just one framework model and to explain the different parameter regimes or physiological properties necessary for each mechanism (such as high or low excitability, corresponding to normal or ischemic tissue, spiral tip trajectory types, and tissue structures such as rotational anisotropy and periodic boundary conditions). Each mechanism is compared with data from other ionic models or experiments to illustrate that they are not model-specific phenomena. Movies showing all the breakup mechanisms are available at http://arrhythmia.hofstra.edu/breakup and at ftp://ftp.aip.org/epaps/chaos/E-CHAOEH-12-039203/ INDEX.html. The fact that many different breakup mechanisms exist has important implications for antiarrhythmic drug design and for comparisons of fibrillation experiments using different species, electromechanical uncoupling drugs, and initiation protocols. (c) 2002 American Institute of Physics.

Reproducing Cardiac Restitution Properties Using the Fenton–Karma Membrane Model

“…A closer match of the action potential shape can be achieved using the four-variable model recently proposed by Fenton. 6 However, the four-variable model has 22 parameters instead of 13, which would complicate the matching procedure. Table 2 summarizes the effects of each parameter of the FKCRN model on the restitution curves.…”

Negative Tension of Scroll Wave Filaments and Turbulence in Three-Dimensional Excitable Media and Application in Cardiac Dynamics

“…2(c). It means it will form loops and if the filament touches a boundary, it will result in the filament breaking into two pieces, leading to filament multiplication (Biktashev et al 1994;Fenton et al 2002;Alonso et al 2003;Gray and Jalife 1998). This regime has received different names from different authors, e.g., autowave turbulence (Biktashev 1998), scroll wave turbulence (Zaritski et al 2004), or Winfree turbulence (Alonso et al 2003).…”

“…This regime has received different names from different authors, e.g., autowave turbulence (Biktashev 1998), scroll wave turbulence (Zaritski et al 2004), or Winfree turbulence (Alonso et al 2003). In simple models, positive tension occurs for a medium with high excitability, i.e., low excitation threshold and/or slow inhibitor dynamics, while negative tension occurs for a medium with low excitability (Brazhnik et al 1987;Fenton et al 2002;Alonso et al 2003).…”

“…The transition of a single spiral state into turbulent pattern is referred to as spiral breakup and was studied in models of cardiac tissue for more than 20 years (Panfilov and Holden 1990;Bär and Eiswirth 1993;Karma 1993;Panfilov and Hogeweg 1993;Panfilov and Pertsov 2001). Possible scenarios of spiral breakup in models of cardiac tissue are surveyed in Panfilov and Pertsov (2001) and Fenton et al (2002). The most discussed mechanisms include dynamic instabilities, e.g., those induced by steep restitution curves (Panfilov and Holden 1990;Karma 1993), heterogeneity (Moe et al 1964), and more recently mechano-electric feedback ).…”

“…However, the exact mechanism of onset of chaotic activity patterns in the heart in real conditions remains unknown. Currently, researchers believe that the mechanism of VF may be different in distinct conditions, and thus studying of various mechanisms of onset of turbulence in excitable medium is important (Fenton et al 2002). It is widely accepted that one of the factors important for the onset of VF is the three-dimensional (3D) structure of the heart.…”