title: Differentiation of atypical atrioventricular node re-entrant tachycardia from orthodromic reciprocating tachycardia using a septal accessory pathway by the response to ventricular pacing.
abstract: OBJECTIVE
  The purpose of this study was to determine whether the response to ventricular pacing during tachycardia is useful for differentiating atypical atrioventricular node re-entrant tachycardia (AVNRT) from orthodromic reciprocating tachycardia (ORT) using a septal accessory pathway.
  
  
  BACKGROUND
  Although it is usually possible to differentiate atypical AVNRT from ORT using a septal accessory pathway, a definitive diagnosis is occasionally elusive.
  
  
  METHODS
  In 30 patients with atypical AVNRT and 44 patients with ORT using a septal accessory pathway, the right ventricle was paced at a cycle length 10 to 40 ms shorter than the tachycardia cycle length (TCL). The ventriculo-atrial (VA) interval and TCL were measured just before pacing. The interval between the last pacing stimulus and the last entrained atrial depolarization (stimulus-atrial [S-A] interval) and the post-pacing interval (PPI) at the right ventricular apex were measured on cessation of ventricular pacing.
  
  
  RESULTS
  All 30 patients with atypical AVNRT and none of the 44 patients with ORT using a septal accessory pathway had an S-A-VA interval >85 ms and PPI-TCL >115 ms.
  
  
  CONCLUSIONS
  The S-A-VA interval and PPI-TCL are useful in distinguishing atypical AVNRT from ORT using a septal accessory pathway.
authors.affiliation: Division of Cardiology, Department of Internal Medicine, Rhode Island Hospital, Brown University, Providence, Rhode Island 02905, USA. gmichaud@lifespan.org
authors.forename: G F
authors.initials: GF
authors.lastname: Michaud
authors.forename: H
authors.initials: H
authors.lastname: Tada
authors.forename: S
authors.initials: S
authors.lastname: Chough
authors.forename: R
authors.initials: R
authors.lastname: Baker
authors.forename: K
authors.initials: K
authors.lastname: Wasmer
authors.forename: C
authors.initials: C
authors.lastname: Sticherling
authors.forename: H
authors.initials: H
authors.lastname: Oral
authors.forename: F
authors.initials: F
authors.lastname: Pelosi
authors.forename: B P
authors.initials: BP
authors.lastname: Knight
authors.forename: S A
authors.initials: SA
authors.lastname: Strickberger
authors.forename: F
authors.initials: F
authors.lastname: Morady
mesh_terms: D000328:Adult; D002304:Cardiac Pacing, Artificial; D003937:Diagnosis, Differential; D005260:Female; D006329:Heart Conduction System; D006346:Heart Septum / Q000294:innervation*; D006801:Humans; D008297:Male; D008875:Middle Aged; D013611:Tachycardia, Atrioventricular Nodal Reentry / Q000175:diagnosis* / Q000628:therapy; D013614:Tachycardia, Paroxysmal / Q000175:diagnosis* / Q000628:therapy