Introduction: The diff eren al diagnosis of wide complex tachycardia (WCT) is wide and complex. Accurate iden fi ca on of the tachycardia mechanism is essen al for successful abla on. We study the role, accuracy and usefulness of specifi c pacing maneuver that can simple and immediately Clarify the tachycardia mechanism in the electrophysiology laboratory.         

Methods: 28 pa ents (33.1+11.9 years) with documented WCT underwent conven onal EPS. During the tachycardia, atrial overdrive pacing was performed. The following responses were observed: (1) a change of the QRS  morphology during atrial pacing and (2) the fi rst return electrogram of the tachycardia, whether occurring in the atrium (AVA response) or in the ventricle (AVVA response). The postpacing interval will be measured from the fi rst paced atrial electrogram to the fi rst arrived atrial electrogram at the pacing site. Conclusion: The response to atrial overdrive pacing during WCT with 1:1 AV rela onship can rapidly diagnose or rule out VT as a mechanism of tachycardia and diagnose wide complex tachycardia mechanism.