title: A technique for the rapid diagnosis of wide complex tachycardia with 1:1 AV relationship in the electrophysiology laboratory.
abstract: BACKGROUND
  The differential diagnosis of wide complex tachycardia (WCT) with 1:1 atrioventricular (AV) relationship is broad. Accurate identification of the tachycardia mechanism is essential for successful ablation. We suggest a simple pacing maneuver that can immediately clarify the tachycardia mechanism in the electrophysiology laboratory.
  
  
  METHODS
  Eight consecutive patients (four males, 32 +/- 14 years) demonstrating stable sustained WCT with persistent 1:1 AV relationship during electrophysiologic testing were included in this study. 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 first return electrogram of the tachycardia, whether occurring in the atrium (AVA response) or in the ventricle (AVVA response).
  
  
  RESULTS
  Atrial overdrive pacing was successfully performed in all patients. It was associated with either a change or narrowing of the QRS in all ventricular tachycardia (VT) patients but not in supraventricular tachycardia (SVT) patients. All VT patients had an AVVA response upon cessation of atrial overdrive pacing as opposed to AVA response in SVT patients, P = 0.029.
  
  
  CONCLUSIONS
  The response to atrial overdrive pacing during WCT with 1:1 AV relationship can rapidly diagnose or rule out VT as a mechanism of tachycardia.
authors.affiliation: Cardiology Division, Queen Elizabeth II Health Sciences Center, Dalhousie University, Halifax, Nova Scotia, Canada.
authors.forename: Amir
authors.initials: A
authors.lastname: Abdelwahab
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Gardner
authors.forename: Magdy N
authors.initials: MN
authors.lastname: Basta
authors.forename: Ratika
authors.initials: R
authors.lastname: Parkash
authors.forename: Aamir
authors.initials: A
authors.lastname: Khan
authors.forename: John L
authors.initials: JL
authors.lastname: Sapp