Spatial dynamics of atrial activity assessed by the vectorcardiogram: from sinus rhythm to atrial fibrillation.

AIM This study aims at developing methods for extracting spatiotemporal information about the electric activity of the atria from electrocardiographic signals, in particular during atrial fibrillation. METHODS 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 atrial surface as well as on the thorax surface. In all, 22 different types of atrial electric activity were generated, 20 of which related to atrial fibrillation (AF). The spatiotemporal behaviour of the 'true' equivalent dipole expression of these activities was documented as well as those of their estimation based on body surface potentials, the vectorcardiogram. Measures were developed for describing the spatial complexity of atrial signals as observed in the 'atrial' vectorcardiogram. RESULTS Coherence between time course of the vectorcardiogram and the electrical atrial activity of the simulated sinus rhythm and typical atrial flutter has been observed. Identification of the local extremes of the distribution of instantaneous vector orientations revealed the location of stable and single atrial activity sources. Moreover, the spatial complexity of the vectorcardiogram can be quantified in a very natural way by the proposed features and their visualization. CONCLUSIONS The proposed analysis extracts spatial information that has hitherto remained unnoticed in non-invasive studies on atrial fibrillation (AF).