title: Differential ventricular entrainment: a maneuver to differentiate AV node reentrant tachycardia from orthodromic reciprocating tachycardia.
abstract: BACKGROUND
  Distinguishing atrioventricular node reentry (AVNRT) from orthodromic reentrant tachycardia (ORT) utilizing an accessory pathway (AP) can sometimes be challenging. A pacing maneuver that reliably distinguishes between the two would be of value.
  
  
  OBJECTIVE
  This study sought to assess the utility of differential entrainment for the diagnosis of supraventricular tachycardia.
  
  
  METHODS
  Consecutive patients underwent prospective electrophysiological study of regular paroxysmal supraventricular tachycardia. Overdrive pacing with entrainment of tachycardia from each of the right ventricular apex and right ventricular base was performed. The post-pacing interval (PPI), PPI minus the tachycardia cycle length and corrected for AV node decrement (cPPI-TCL), and the ventriculoatrial (VA) interval (last RV pacing stimulus to last entrained high right atrial signal) were calculated at each site.
  
  
  RESULTS
  Entrainment at both RV sites was achieved in 35 patients, 16 with typical AVNRT, 1 with atypical AVNRT, and 18 with ORT (13 left free wall, 3 right free wall, and 2 septal APs). The cPPI-TCL and VA intervals were significantly longer from base than apex in AVNRT (cPPI-TCL 61 ms longer, VA 38 ms longer, both P < .0001). There was no significant difference in differential entrainment intervals in patients with ORT. A differential cPPI-TCL >30 ms or VA interval >20 ms identified patients with AVNRT with a positive predictive value, negative predictive value, sensitivity, and specificity of 100%.
  
  
  CONCLUSIONS
  Differential ventricular entrainment is a useful tool for diagnosing between AVNRT and ORT. A differential cPPI-TCL >30 ms or VA interval of >20 ms reliably predicts AVNRT.
authors.affiliation: Division of Cardiology, University Hospital, London Health Sciences Centre, London, Ontario, Canada. oliver.segal@uclh.nhs.uk
authors.forename: Oliver R
authors.initials: OR
authors.lastname: Segal
authors.forename: Lorne J
authors.initials: LJ
authors.lastname: Gula
authors.forename: Allan C
authors.initials: AC
authors.lastname: Skanes
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Krahn
authors.forename: Raymond
authors.initials: R
authors.lastname: Yee
authors.forename: George J
authors.initials: GJ
authors.lastname: Klein