Teaching points with 3-dimensional mapping of cardiac arrhythmias: taking points: activation mapping.

The map obtained of a tachycardia is greatly influenced by how meticulously individual activation points are annotated to indicate the timing of activation. The annotation window is typically set to display surface leads and intracardiac electrograms.1,2 These include the electrogram or ECG lead used as the timing reference as well as the bipolar and unipolar signals from the mapping catheter.3–5 Assuming that the point of reference electrograms remains stable and the window of interest and tachycardia cycle length are unchanged, the consistency of annotating the timing of mapping catheter– derived electrograms is the defining factor for the accuracy of the map. The operator must have a consistent plan as to how to annotate the electrogram timing as well as a method of handling double potentials and fragmented signals.