Electrical activity of the common His bundle can be recorded from an electrode catheter placed directly over it. The recording obtained in this manner, shown here in the lower tracing, is referred to as a His bundle electrogram. The upper tracing is the simultaneously recorded lead II electrocardiogram. The various deflections on the His Bundle electrogram represent atrial depolarization (A), depolarization of the common His bundle( H) and ventricular depolarization (V).
