Characterizing His-Purkinje system signals observed at the body surface. A model study

A computer model of the His-Purkinje system (HPS), based on human geometry, has been developed and used in conjunction with an atrial model and an inhomogeneous torso model to calculate electrocardiograms (ECGs) and isofield potential and magnetic maps. The calculated electric potential maximum for penetrating His bundle (HB) activity is 0.6 microV, somewhat smaller than reported by others. A calculated ECG of combined atrial and HPS activity indicates that atrial repolarization contributes to the ramp pattern observed in the PR segment. Simulated isofield distributions indicate two features that should be present in serial-measured HPS maps: (1) maps preceding HB activity should be included to illustrate the nature of the onset of HB activity and (2) maps should show a change in the location and magnitude of the extrema commensurate with the change in direction and magnitude of the source current circumscribed by the anatomy of the HB and bundle branches.