The standard nomenclature for pacing is a five-letter designation for the mode of pacing and sensing of intrinsic electrical (cardiac) activity. In the setting of urgent or emergent pacing, only the first three letters of the Inter-Society Commission for Heart Disease Resources (ICHD) are typically used (Table 79.1). The first letter refers to the cardiac chamber paced, the second letter represents the chamber sensed, and the third letter represents the mode, or what happens in response to the sensing. The latter two-letter designations are generally used in internal pacemakers and reflect more sophisticated programming that is beyond the scope of this chapter.

The method used to pace patients depends on the wires that are used (i.e., whether there is capability to pace the atria, ventricles, or both) and the mode designated on the pacer box. The capability to pace one or both chambers depends on the type (or number) of wires placed or the type of transvenous device that has been placed. In the setting of post–cardiac surgery patients, the ground wire is placed in the positive pole of the pacer box. By convention, the ground wire is the longer of the two ventricular wires or a newly placed skin lead. For atrial epicardial wires, either can be used as the grounding wire. In the

setting of transvenous pacing, the positive lead on the wire is placed in the positive pole of the pacer box.