| Abstract: | In 16 dogs, by appropriate filtering and digital averaging on a PDP-9 computer, we were able to enhance the detection of electrical activity of interest in the P-R segment of the electrocardiogram. In instances (1) when such activity in the surface record coincided temporally with the internal recording from the bundle of His area, (2) when, with atrioventricular nodal block, the electrical activity of interest continued to be associated with the internally recorded His bundle deflection and not with atrial activity, and (3) when, with production of transmission delay between the bundle of His and the ventricle, the surface signal of interest continued to be associated with the internal His bundle deflection, a common signal source was considered likely. In certain instances the surface signal of interest in the P-R segment occurred well after the internally recorded His bundle deflection but about 15 msec before the earliest evidence of ventricular activity. In these instances, when the tests cited were applied and the blip of interest was associated with ventricular activity, the origin of the blip was thought to be in the region of the bundle branches.In the 16 animals studied, one or more pieces of the evidence described were present to localize the origin of the signal. In seven animals, the signal was thought to originate from the bundle of His, in six from the region of the bundle branches and in three from both the bundle of His and bundle branches. |
