Multistability as intrinsic property of a single cardiac cell: a simulation study

Multistability mechanism or the appearance of coexisting rhythms at periodical stimulation of single cardiac cells is explored. A computation analysis is carried out using the phase 1 Luo and Rudy action potential model. Using double stage protocol of stimulation we have changed continuously the moment of application of the premature or delayed stimulus or the so-called ´coupling interval´ and investigated the stable states of action potential duration. A multistability zone is established implying a stimulation frequency range where different initial conditions (premature or delayed stimulus application moments) lead to different stable rhythms. Basins of attraction are discovered on the transmembrane potential curve. Each basin is characterized by a set of initial conditions leading to a certain stable rhythm. Basins of attraction are shown to coexist for both simple and complex entrainment modes, which results in multistability. Obtained basins of attraction of complex rhythms on the curves of transmembrane potential are expected to be linked with the occurrence of cardiac vulnerable windows on ECG records during which extra stimuli can induce life threatening arrhythmias.