Challenges in modelling human heart's total excitation

Using a three-dimensional computer model of the human ventricular myocardium, we studied the role of ventricular architecture and conduction system in generating intramural activation patterns and the extracardiac electric field. The model represents the myocardium as an anisotropic bidomain; it incorporates detailed anatomical features, including intramural fiber rotation, the differences in the fiber arrangement of the trabeculae and papillary muscles, and a conduction system. Ectopic activation was elicited at various depths, and "normal" activation was initiated via the conduction system. Extracardiac potentials were calculated throughout each activation sequence. The simulated epicardial potential maps resembled those measured in canine hearts, featuring a central minimum accompanied by two maxima in the early stages of ectopic activation, with the axis joining these extrema approximately parallel to the fibers near the pacing site. The simulated isochrones for the "normal" activation had characteristics very similar to those observed in isolated perfused human hearts.