title: Number of Beats in the Transition Zone With Fixed SA Interval during Right Ventricular Overdrive Pacing Determines Accessory Pathway Location in Orthodromic Reentrant Tachycardia.
abstract: BACKGROUND
  Ventricular overdrive pacing (VOP) produces reset during the transition zone (TZ) of QRS fusion in orthodromic reentrant tachycardia (ORT) and after the TZ in atrioventricular nodal reentrant tachycardia (AVNRT), and this represents a simple diagnostic maneuver to differentiate the two tachycardia mechanisms.
  
  
  OBJECTIVE
  The purpose of this study was to determine whether the number of beats with reset in the TZ predicts accessory pathway (AP) location in ORT.
  
  
  METHODS
  We retrospectively reviewed 57 patients with ORT (21 left-sided AP, 20 septal AP, and 16 right-sided AP) and 20 patients with AVNRT (19 typical AVNRT and one atypical AVNRT) who underwent VOP from the right ventricular apex. We analyzed the number of beats with reset during or after the TZ, demonstrated by fixed ventricular stimulus-atrial (SA) interval during VOP.
  
  
  RESULTS
  The overall mean tachycardia cycle length [CL] minus VOP CL was 22.6 ± 7.5 ms with no statistical difference between the groups (P = 0.480). The mean number of beats in the TZ with fixed SA interval was 2.5 ± 1.4 for the whole ORT group, 1.1 ± 0.4 for left-sided AP (range 1-2), 2.8  ±  0.9 for septal AP (range 1-5), and 4.0 ± 0.9 for right-sided AP (range 3-6) (P < 0.001). Using a cutoff >2 beats distinguished right- versus left-sided AP in all cases.
  
  
  CONCLUSIONS
  Assessing the number of beats in the TZ with fixed SA interval during VOP helps to determine AP location in ORT and adds valuable information to an established simple diagnostic pacing maneuver, especially when a two-catheter simplified approach is employed.
authors.affiliation: Cardiac Arrhythmia and Electrophysiology Unit, Department of Cardiology, Hospital Virgen de la Salud, Toledo, Spain.|Karolinska University Hospital, Karolinska Institutet at Department of Cardiology, Stockholm, Sweden.
authors.forename: Finn
authors.initials: F
authors.lastname: Akerström
authors.affiliation: Cardiac Arrhythmia and Electrophysiology Unit, Department of Cardiology, Hospital Virgen de la Salud, Toledo, Spain.
authors.forename: Marta
authors.initials: M
authors.lastname: Pachón
authors.affiliation: Arrhythmia Unit, Department of Cardiology, Complejo Asistencial Universitario de Burgos, Burgos, Spain.
authors.forename: Francisco Javier
authors.initials: FJ
authors.lastname: García-Fernández
authors.affiliation: Arrhythmia Unit, Department of Cardiology, Hospital Universitario La Paz, Madrid, Spain.
authors.forename: Óscar
authors.initials: Ó
authors.lastname: Salvador-Montañés
authors.affiliation: Karolinska University Hospital, Karolinska Institutet at Department of Cardiology, Stockholm, Sweden.
authors.forename: Mats
authors.initials: M
authors.lastname: Jensen-Urstad
authors.affiliation: Cardiac Arrhythmia and Electrophysiology Unit, Department of Cardiology, Hospital Virgen de la Salud, Toledo, Spain.
authors.forename: Alberto
authors.initials: A
authors.lastname: Puchol
authors.affiliation: Arrhythmia Unit, Department of Cardiology, Hospital Universitario La Paz, Madrid, Spain.
authors.forename: Rafael
authors.initials: R
authors.lastname: Peinado
authors.affiliation: Arrhythmia Unit, Department of Cardiology, Complejo Asistencial Universitario de Burgos, Burgos, Spain.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Salgado
authors.affiliation: Karolinska University Hospital, Karolinska Institutet at Department of Cardiology, Stockholm, Sweden.
authors.forename: Per
authors.initials: P
authors.lastname: Insulander
authors.affiliation: Cardiac Arrhythmia and Electrophysiology Unit, Department of Cardiology, Hospital Virgen de la Salud, Toledo, Spain.
authors.forename: Luis
authors.initials: L
authors.lastname: Rodríguez-Padial
authors.affiliation: Cardiac Arrhythmia and Electrophysiology Unit, Department of Cardiology, Hospital Virgen de la Salud, Toledo, Spain.
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Arias
mesh_terms: D058606:Accessory Atrioventricular Bundle / Q000175:diagnosis* / Q000628:therapy*; D000328:Adult; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D003936:Diagnosis, Computer-Assisted / Q000379:methods; D004562:Electrocardiography / Q000379:methods*; D005260:Female; D006339:Heart Rate; D006352:Heart Ventricles; D006801:Humans; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013611:Tachycardia, Atrioventricular Nodal Reentry / Q000175:diagnosis* / Q000628:therapy*; D016896:Treatment Outcome
keywords: accessory pathway; entrainment; orthodromic reentrant tachycardia; radiofrequency ablation; supraventricular tachycardia