title: Junctional tachycardia: a useful marker during radiofrequency ablation for atrioventricular node reentrant tachycardia.
abstract: OBJECTIVE
  The aim of this study was to evaluate junctional tachycardia as a useful marker during radiofrequency ablation for atrioventricular (AV) node reentrant tachycardia.
  
  
  BACKGROUND
  Junctional tachycardia appears to be a response of the atrioventricular node to injury and is seen during both radiofrequency AV node ablation and slow and fast pathway ablation for AV node reentrant tachycardia. We hypothesized that junctional tachycardia heralding AV node block and that associated with slow or fast pathway ablation may have different characteristics that could be useful in preventing inadvertent AV block.
  
  
  METHODS
  Characteristics of junctional tachycardia were examined after 59 radiofrequency ablation sessions in 53 consecutive patients with a mean age (+/- SD) of 41.6 +/- 16.5 years. Type 1 junctional tachycardia was followed by transient second- or third-degree AV block (n = 5) or permanent third-degree AV block (n = 1). Type 2 junctional tachycardia was followed by normal AV conduction (n = 53).
  
  
  RESULTS
  Fifty-one patients had typical AV node reentrant tachycardia, and two patients had atypical tachycardia. Fast pathway ablation was attempted during 6 sessions and slow pathway ablation during 53 sessions. Patients underwent 15.3 +/- 10 radiofrequency applications, with a mean duration of 24 +/- 9.7 s. Junctional tachycardia was observed an average of 2.8 +/- 1.8 times per ablation session. Type 1 junctional tachycardia had a significantly faster rate than that of type 2 (cycle length 363 +/- 44 vs. 558 +/- 116, p < 0.001). In addition, type 1 junctional tachycardia was associated with predominantly ventriculoatrial block whereas type 2 was associated with predominantly 1:1 ventriculoatrial conduction (2 of 6 vs. 47 of 53 episodes, p < 0.05).
  
  
  CONCLUSIONS
  We conclude that junctional tachycardia leading to AV block can be recognized by a faster junctional rate and ventriculoatrial block. This is a useful marker of impending AV block during slow and fast pathway ablation.
authors.affiliation: Department of Medicine, University of Western Ontario, London, Canada.
authors.forename: R K
authors.initials: RK
authors.lastname: Thakur
authors.forename: G J
authors.initials: GJ
authors.lastname: Klein
authors.forename: R
authors.initials: R
authors.lastname: Yee
authors.forename: H W
authors.initials: HW
authors.lastname: Stites
mesh_terms: D000328:Adult; D017115:Catheter Ablation / Q000009:adverse effects*; D004562:Electrocardiography; D005260:Female; D006327:Heart Block / Q000209:etiology / Q000503:physiopathology* / Q000517:prevention & control; D006801:Humans; D008297:Male; D008875:Middle Aged; D013610:Tachycardia / Q000209:etiology* / Q000503:physiopathology; D013611:Tachycardia, Atrioventricular Nodal Reentry / Q000503:physiopathology / Q000601:surgery*