Virtual electrode effects around an artificial heterogeneity during field stimulation of cardiac tissue

Woods, Marcella C.; Sidorov, Veniamin Y.; Holcomb, Mark R.; Beaudoin, Deborah Langrill; Roth, Bradley J.; Wikswo, John P.

doi:10.1016/j.hrthm.2005.11.003

Cited by 24 publications

(21 citation statements)

References 3 publications

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“…In particular, the results show how the presence of the insulating vessel wall reduces the magnitude of the dipolar surface VE, causing the polarity of the surface VE to swap (relative to the case with no vessel wall); an effect first noticed in [20, 21]. When the blood-vessel is represented by an internal boundary, on which the intra- and extracellular current-densities vanish (results not shown), the induced VE is similar to that induced in the case with an insulating vessel-wall, and consistent with experimental observations [25]. …”

Section: Discussionsupporting

confidence: 84%

“…The VE around an insulating cylinder was observed experimentally using optical-mapping in [25]—it can be seen that the VE patterns shown in Fig 1 (B) in [25] are qualitatively similar to those presented in Fig 8 with the presence of an insulating vessel wall. We recomputed the VE field around perfect insulators to confirm that the VE pattern is indeed similar—see Fig 9.…”

Section: Resultssupporting

confidence: 63%

“…Previous modelling and experimental studies have suggested the importance of vessels in creating sources of excitation upon field stimulation [4, 20, 21, 25]. In this study, we showed how the contributions to the vessel VE are composed, mathematically, in terms of the zeroth and first-order contributions, and physically, from current transiting the vessel surface and current redistribution due to conductivity anisotropy, respectively.…”

Section: Discussionmentioning

confidence: 57%

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Virtual electrodes around anatomical structures and their roles in defibrillation

2017

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BackgroundVirtual 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.Methods and resultsThe 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.ConclusionsThe 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.

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Section: Discussionsupporting

confidence: 84%

Section: Resultssupporting

confidence: 63%

Section: Discussionmentioning

confidence: 57%

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Virtual electrodes around anatomical structures and their roles in defibrillation

2017

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“…4,5 Figures 9 and 10 show the action of a very short ͑200 s͒, very strong ͑500 V͒ shock applied to a whole heart in a bath. The optical traces were made using a voltage-sensitive fluorescent dye, a high-speed camera, and processing to normalize the signal against a background.…”

Section: Resultsmentioning

confidence: 99%

A high-voltage cardiac stimulator for field shocks of a whole heart in a bath

Mashburn

Hinkson²,

Woods

et al. 2007

Review of Scientific Instruments

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Defibrillators are a critical tool for treating heart disease; however, the mechanisms by which they halt fibrillation are still not fully understood and are the subject of ongoing research. Clinical defibrillators do not provide the precise control of shock timing, duration, and voltage or other features needed for detailed scientific inquiry, and there are few, if any, commercially available units designed for research applications. For this reason, we have developed a high-voltage, programmable, capacitive-discharge stimulator optimized to deliver defibrillation shocks with precise timing and voltage control to an isolated animal heart, either in air or in a bath. This stimulator is capable of delivering voltages of up to 500 V and energies of nearly 100 J with timing accuracy of a few microseconds and with rise and fall times of 5 micros or less and is controlled only by two external timing pulses and a control computer that sets the stimulation parameters via a LABVIEW interface. Most importantly, the stimulator has circuits to protect the high-voltage circuitry and the operator from programming and input-output errors. This device has been tested and used successfully in field shock experiments on rabbit hearts as well as other protocols requiring high voltage.

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“…(29) We did not directly measure field gradient values within the heart tissue because Woods et al (30) have shown that measuring devices, such as plunge electrodes, cause unintended experimental artifacts and we did not attempt to calculate them because virtual electrode polarization, (28) and tissue heterogeneity make it impossible without exceedingly sophisticated modeling using real anatomical measurements for each preparation.…”

Section: Methodsmentioning

confidence: 99%

Atria are more susceptible to electroporation than ventricles: Implications for atrial stunning, shock-induced arrhythmia and defibrillation failure

Fedorov¹,

Kostecki²,

Hemphill³

et al. 2008

Heart Rhythm

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Virtual electrode effects around an artificial heterogeneity during field stimulation of cardiac tissue

Cited by 24 publications

References 3 publications

Virtual electrodes around anatomical structures and their roles in defibrillation

Virtual electrodes around anatomical structures and their roles in defibrillation

A high-voltage cardiac stimulator for field shocks of a whole heart in a bath

Atria are more susceptible to electroporation than ventricles: Implications for atrial stunning, shock-induced arrhythmia and defibrillation failure

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