An In-Silico Study into the Impact of Electrophysiological Variability at the Cellular Level on the Re-entry Patterns in Atrial Fibrillation

Modelling the atria in-silico has become an important method in understanding atrial behaviour. Atrial models typically include regional electrophysiological variability, but neglect cellular variability. The aim of the study is to determine the impact of cellular electrophysiological variability on ectopic beats. Using a population of models approach to introduce regional and cellular variability into the atrial model, ectopic beats were initiated in two locations. Six ectopic beats were applied at a BCL of 130-160ms. The variable model was compared with an equivalent regional homogenous model. Using consistent tissue CV between models, in both the healthy and AF remodeled cases the average model total activation time was later than the variable model (a delay of 26ms and 14ms respectively). After matching activation times, repolarization was later in the average than the variable models. Latest APD90 in the AF remodeled cases were 268ms for the average and 256ms in the variable model. This resulted in a difference in propagation of the ectopic beat. In conclusion, cellular variability has a significant impact on both the depolarization and repolarization phases in the atria for the healthy and AF cases.