title: Virtual electrodes around anatomical structures and their roles in defibrillation.
abstract: BACKGROUND
  Virtual electrodes from structural/conductivity heterogeneities are known to elicit wavefront propagation, upon field-stimulation, and are thought to be important for defibrillation. In this work we investigate how the constitutive and geometrical parameters associated with such anatomical heterogeneities, represented by endo/epicardial surfaces and intramural surfaces in the form of blood-vessels, affect the virtual electrode patterns produced.
  
  
  RESULTS
  The steady-state bidomain model is used to obtain, using analytical and numerical methods, the virtual electrode patterns created around idealized endocardial trabeculations and blood-vessels. The virtual electrode pattern around blood-vessels is shown to be composed of two dominant effects; current traversing the vessel surface and conductivity heterogeneity from the fibre-architecture. The relative magnitudes of these two effects explain the swapping of the virtual electrode polarity observed, as a function of the vessel radius, and aid in the understanding of the virtual electrode patterns predicted by numerical bidomain modelling. The relatively high conductivity of blood, compared to myocardium, is shown to cause stronger depolarizations in the endocardial trabeculae grooves than the protrusions.
  
  
  CONCLUSIONS
  The results provide additional quantitative understanding of the virtual electrodes produced by small-scale ventricular anatomy, and highlight the importance of faithfully representing the physiology and the physics in the context of computational modelling of field stimulation.
authors.affiliation: Division of Imaging Sciences and Biomedical Engineering, King's College London, St. Thomas' Hospital, London, United Kingdom.
authors.forename: Adam
authors.identifier: http://orcid.org/0000-0001-9475-0205
authors.initials: A
authors.lastname: Connolly
authors.affiliation: IHU Liryc, Electrophysiology and Heart Modeling Instituté, fondation Bordeaux Université, F-33600 Pessac-Bordeaux, France.|Univ. Bordeaux, IMB, UMR 5251, F-33400 Talence, France.
authors.forename: Edward
authors.initials: E
authors.lastname: Vigmond
authors.affiliation: Division of Imaging Sciences and Biomedical Engineering, King's College London, St. Thomas' Hospital, London, United Kingdom.
authors.forename: Martin
authors.initials: M
authors.lastname: Bishop
mesh_terms: D004554:Electric Countershock / Q000295:instrumentation*; D004566:Electrodes; D006801:Humans; D008962:Models, Theoretical