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Figure 1 Example of the first diagnostic pacing maneuver. Shown are surface electrograms I, II, III, V1, and intracardiac recordings from the high right atrium (HRA), His-bundle electrogram (HBE), and right ventricular apex (RVA). The tachycardia is entrained with atrial pacing. The VA interval of the return beat is the same as the VA interval of the tachycardia. This observation, referred to as "VA linking," would not be expected during atrial tachycardia because atrial activation is not dependent on ventricular activation. S = stimulus.