title: Reanalysis of the "pseudo A-A-V" response to ventricular entrainment of supraventricular tachycardia: importance of his-bundle timing.
abstract: BACKGROUND
  The sequence of atrial and ventricular electrograms following termination of ventricular pacing during supraventricular tachycardia has been shown to reliably differentiate atrial tachycardia from atrioventricular nodal reentrant tachycardia (AVNRT) and atrioventricular reentrant tachycardia (AVRT). However in patients with long HV intervals, this may be misleading due to a pseudo "A-A-V" response. The aim of the present study is to see if inclusion of the timing of the His-bundle in the electrogram response (ER) following ventricular pacing would reliably identify the mechanism of tachycardia in patients with long HV intervals.
  
  
  METHODS
  Eight patients (7 men) with AVNRT and underlying bundle branch block and long HV (>55 msec) intervals underwent ventricular pacing at 10-40 msec shorter than the tachycardia cycle length during SVT. The ER was classified as "A-A-H" or "A-H" depending on the number of atrial electrograms (A) prior to His deflection following VEP.
  
  
  RESULTS
  The ER following ventricular pacing was classified as A-H in all 8 patients. However, using conventional classification the response was A-A-V in 5 of 8 patients due to delayed ventricular activation secondary to long HV intervals and would erroneously suggest atrial tachycardia. The ER was A-V in only 1 of 8 patients. In the remaining 2 patients the A and V electrograms were simultaneous.
  
  
  CONCLUSIONS
  Incorporating the His-bundle in the ER following ventricular pacing would eliminate the pseudo "A-A-V" response in patients with AVNRT and long HV intervals. Labeling the response to ventricular pacing as "A-H" or "A-A-H" is simple and more accurate.
authors.affiliation: Division of Cardiology, Cardiac Electrophysiology, McGuire VA Medical Center, Medical College of Virginia at Virginia Commonwealth University, Richmond, Virginia 23249, USA. p.vijayaraman@med.va.gov
authors.forename: Pugazhendhi
authors.initials: P
authors.lastname: Vijayaraman
authors.forename: Benjamin P
authors.initials: BP
authors.lastname: Lee
authors.forename: Gautham
authors.initials: G
authors.lastname: Kalahasty
authors.forename: Mark A
authors.initials: MA
authors.lastname: Wood
authors.forename: Kenneth A
authors.initials: KA
authors.lastname: Ellenbogen
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002036:Bundle of His / Q000503:physiopathology*; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D004562:Electrocardiography; D005260:Female; D005500:Follow-Up Studies; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D013611:Tachycardia, Atrioventricular Nodal Reentry / Q000503:physiopathology / Q000628:therapy*; D016896:Treatment Outcome