Abstract
Fibroblasts are nonexcitable cells that are sometimes coupled with
excitable cells (cardiomyocytes). Due to a higher resting potential,
these cells may act as a current source or sink and therefore disturb
the electrical activity of the surrounding excitable cells. The possible
occurrence of spontaneous pacemaker activity resulting from these
electrotonic interactions was investigated in a theoretical model
of two coupled cells as well as in a multicellular fiber model based
on the Courtemanche kinetics. The results indicate that repeated
spontaneous activations can be observed after an alteration in the
activation and recovery properties of the sodium current (changes
in excitability properties), provided that the difference in the
resting potential as well as the coupling between the excitable and
nonexcitable cells is sufficiently high. This may constitute a mechanism
of focal sources triggering arrhythmias such as atrial fibrillation.
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