PACED ACTIVATION MAPPING REVEALS ORGANIZATION OF MYOCARDIAL FIBERS - A SIMULATION STUDY

Pacing Reveals Fiber Orientation in 3D Bidomain. Introduction: A three -dimensional bidomain model of a block section of both the right and l eft ventricular walls that included rotational anisotropy and fiber cu rvature was used to investigate potential distributions generated duri ng paced activation mapping, Unlike previous large-scale tissue models , the extracellular stimulus was included, Methods and Results: The mo del was used to test the hypothesis that information about the underly ing tissue structure (surface fiber angle gradients, amount of fiber r otation per unit depth, and anisotropy) can be extracted from surface potential distributions during stimulation, Results from distributions during stimulation were compared to those obtained using the distribu tions during activation, To better correlate results to possible exper imental measurements, the analysis was performed using a 21 x 21 grid of ''electrode'' sites, each separated by 1 mm, Fiber orientation was estimated from the surface data by: (1) curve-fitting the elliptical s hape of the epicardial potential distribution during stimulation; (2) identifying the location of the potential maxima leading the wavefront during early activation; and (3) for epicardial stimuli, curve-fittin g the elliptical shape of the activation isochrones. Results show that surface potential distributions from the stimulus can be used to esti mate fiber orientation; however, the accuracy of the reconstruction is highly dependent on the amount of fiber rotation per unit depth, Conc lusions: Extracellular potential data during and after stimulation is shown to reflect the organization of myocardial fibers and, as such, c ould be used to characterize the three-dimensional anisotropic electri cal properties in situ.