A dynamic electrical record of the pathway of human His bundle activation from surface mapping.

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Abstract
Body surface potential maps of human His bundle activity have been difficult to product for two reasons: (1) The peak surface potentials are often less than 5 muv, and (2) the simultaneous atrial repolarization potentials frequently exceed 100 muv. We have therefore amplified surface signals 25 times the standard gain of 1000, and then removed by cross-correlation the static pattern of atrial repolarization for serial 1-msec maps of the P-R segment in five normal men. A consistent finding emerged: a positive anterior chest peak appeared 40 msec before QRS onset, and then-within 10 msec-spread out into a long, low transverse mound before disappearing in 5 more msec. The map data were analytically converted to serial electrical sources: the center of electrical activity moved first slightly down, then directly forward, before retracing its path and disappearing. The retrace and accompanying surface spread-out strongly suggests diverging dipolar sources. Thus the data fit a simple heart source which moves anteriorly and then breaks into two (right and left)-as expected from activation of the bundle of His and its bifurcation into left and right bundle branches.