Key result
Smaller electrodes produce dog-bone shaped virtual cathodes and egg-shaped anodes with larger peak values.
A three-dimensional bidomain model simulation demonstrates that electrode size significantly alters the spatial distribution and shape of virtual electrodes during cardiac defibrillation.
Bidomain simulations of virtual electrodes extend computational models of defibrillation; leaves open experimental validation before clinical relevance.
The virtual electrode (VE) has been recognized as an important factor for success or failure of cardiac defibrillation. Many researches have been performed to study characteristics of the VE. However, there are some questions which remain unanswered. In this study, we developed a simulator to solve a three-dimensional bidomain model and performed several simulations to elucidate the basic characteristics of VE in a simplified cardiac tissue with passive membrane when a constant unipolar cathodal stimulus was applied. The results showed that for smaller electrodes, VE has a typical dog-bone shaped virtual cathode (VC) and two egg-shaped virtual anodes (VAs). The distributions both in intra- and extracellular potentials have concentric ellipsoidal isosurfaces, but their ellipticities are subtly different, producing VE. For larger electrodes, VC becomes larger and has a flat-dish shape rather than dog-bone, and VA becomes smaller and also flattens and collapses. The peak values of VE are larger for smaller electrodes, but their time courses show similar tendency among the different sized electrodes. The change of stimulus strength and polarity only affects the magnitude of VE in a linear manner and the distribution pattern is unchanged. These results provide us fundamental knowledge about VE.
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Suzuki et al. (2006) studied Cardiac defibrillation. Constant unipolar cathodal stimulus was evaluated on Characteristics of virtual electrode (VE) in a simplified cardiac tissue with passive membrane. Simulations of a three-dimensional bidomain model showed that smaller electrodes produce a dog-bone shaped virtual cathode and two egg-shaped virtual anodes, with peak values larger for smaller electrodes.
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