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The aim of this paper is to develop a tool to construct initial conditions for a cardiac propagation model, in which phase singularities are positioned at predefined locations. Our approach relies on the eikonal-diffusion equation (extended to handle reentrant activations) to generate phase maps describing reentries around phase singularities. Through a mapping between phase and cell state, these...
Microscale electrical propagation in the heart can be modeled by a reaction-diffusion system, describing cell and tissue electrophysiology. Macroscale features of wavefront propagation can be reproduced by an eikonal model, a reduced formulation involving only wavefront shape. In this paper, these two approaches are combined to incorporate global information about reentrant pathways into a reaction-diffusion...
This study aims at assessing the relation between the activity level of an ectopic focus and the complexity of the resulting atrial fibrillation (AF) dynamics. Eight different episodes of focal AF were simulated in a 3D model of human atria. To create various AF dynamics, the episodes differed by the location of their focal source. The activity level of a source was quantified by the number of propagating...
The membrane kinetics of human atrial myocytes as formulated by Courtemanche, Ramirez and Nattel has been studied while focussing on its progression toward stationary solutions during long term repetitive stimulation. An algorithm is presented for finding the initial settings for all state variables on the basis of those assumed for the transmembrane potential Vm and the intracellular concentrations...
The correspondence between the firing rates of atrial myocytes during atrial fibrillation and the dominant frequencies observed in the Fourier spectra of the corresponding surface ECG signals was studied. The observations were based on signals simulated using a biophysical model of the atria and of the volume conduction effects of the thorax. Different substrates for AF were generated, each resulting...
This study aims at developing a measure for describing the spatial complexity of atrial signals during atrial fibrillation (AF). A biophysical model of the atria and a volume conductor model of the thorax were used to simulate the atrial electrical activity as expressed on the torso. Features were extracted from the equivalent dipole (VCG) derived from body surface potentials. The robustness of these...
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