Bistability and Correlation with Arrhythmogenesis in a Model of the Right Atrium

Abstract

Abstract-Rapid pacing is an important tool for understanding cardiac arrhythmias. A recent experiment involving rapid pacing of sheep atria indicated that the initiation of atrial arrhythmias may be related to the 1:1/2:1 bistability. To elucidate the mechanism of this relation, this study applied the pacing protocol from the sheep study to an idealized model of the right atrium. The model included all major anatomical features, the sino-atrial node, and the regional differences in the action potential duration (APD). A pacing protocol was applied, in which the basic cycle length (BCL) was decreased in steps of 10 ms until the response switched to 2:1, then BCL was increased. The 1:1-to-2:1 transitions occurred at shorter BCLs than the 2:1-to-1:1 transitions yielding a global bistability window of 60 ms. As in the sheep study, idiopathic waves were observed at BCLs within or near the bistability window. The model was used to quantify the types, prevalence, and persistence of idiopatic waves, study their initiation and termination, and relate them to the model components. The results demonstrate that idiopatic waveforms move with the shift of the bistability window and that they disappear when bistability is eliminated. Thus, this modeling study supports causal relationship between the 1:1/2:1 bistability and the initiation of arrhythmias.

Mechanisms of ventricular arrhythmias: a dynamical systems-based perspective

“…At a still longer time scale of days to months, the heart can remodel, both structurally and functionally, in response to various stressors (3,146,196). Along with the presence of multiple time scales, the nonlinearity of cardiac tissue (67,86,117) can result in complex dynamics from such properties as multistability (53,68,103,150,188,199) and dependence on initial conditions (34,42,68).…”

“…Nevertheless, certain functions of the heart, notably restitution of APD, are known to exhibit a sensitive dependence on initial conditions. (34,42,68,103,150,188). Perhaps these properties and other nonlinear effects, such as multistability, where a system may oscillate between two quasistable states, underlie the seemingly unpredictable emergence of some ventricular tachyarrhythmias.…”

Memory effects, transient growth, and wave breakup in a model of paced atrium

“…It is well-known that paced cardiac tissue displays multistability in zero 20 , one 21 , and two 22,23 dimensions. Transitions between different stable attractors in spatially extended dissipative nonequilibrium systems are in fact not uncommon.…”