Activity level of an atrial ectopic focus observed through the atrial vectorcardiogram: A biophysical model

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 focal fronts originating from that source. The dynamic complexity was quantified through the time course of the atrial vectorcardiogram (VCG) orientation. The eigenvalues of the second-order raw moment matrix of the normalized atrial VCG were used to characterize the spread of spatial distribution of the atrial VCG. A strong correlation was found between the 3^rd eigenvalues and the number of focal fronts. Analyzing the spatial distribution of the atrial VCG could provide information about the activity level of atrial ectopic foci and the complexity of AF dynamics.