title: Differential pacing for distinguishing slow conduction from complete conduction block of the tricuspid-inferior vena cava isthmus after radiofrequency ablation for atrial flutter--role of transverse conduction through the crista terminalis.
abstract: BACKGROUND
  Partial conduction block has been suggested a predictor of recurrence of atrial flutter (AFL).
  
  
  OBJECTIVE
  The aim of this study was to assess transverse conduction by the crista terminalis (CT) as a problem in evaluating isthmus block and the usefulness of differential pacing for distinguishing slow conduction (SC) and complete conduction block (CB) across the ablation line.
  
  
  METHODS
  We assessed 14 patients who underwent radiofrequency catheter ablation of the eustachian valve/ridge-tricuspid valve isthmus for typical AFL. Activation patterns along the tricuspid annulus (TA) suggested incomplete CB across the isthmus. In these patients, atrial pacing was performed from the low posteroseptal (PS) and anteroseptal (AS) right atrium (RA) while the ablation catheter was placed at the ablation line where double potentials (DPs) could be recorded. The pattern of activation of the RA free wall was assessed by a 20-pole catheter positioned along the CT during pacing from the coronary sinus (CS) ostium (CSos) and low lateral RA (LLRA).
  
  
  RESULTS
  Faster transverse conduction across the CT resulted in simultaneous or earlier activation of the distal halo electrodes than of the more proximal electrodes, suggesting incomplete conduction block across the isthmus. CB (13) and SC (1) were detected as changes in the activation times of the first and second components of DPs (DP1, DP2) during PS RA pacing and AS RA. Similar changes in the activation times DP1 and DP2 during AS RA pacing as compared to PS RA reflected SC through the isthmus, whereas increased DP1 activation time and decreased of DP2 activation time reflected complete conduction block across the isthmus.
  
  
  CONCLUSIONS
  Transverse conduction across the CT influences the sequence of activation along the TA after isthmus ablation. Differential pacing can distinguish SC from complete conduction block across the ablation line in the isthmus.
authors.affiliation: Division of Cardiovascular Disease, Department of Medicine, Nihon University School of Medicine, Tokyo, Japan.
authors.forename: Hidezou
authors.initials: H
authors.lastname: Sugimura
authors.forename: Ichiro
authors.initials: I
authors.lastname: Watanabe
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Okumura
authors.forename: Kimie
authors.initials: K
authors.lastname: Ohkubo
authors.forename: Sonoko
authors.initials: S
authors.lastname: Ashino
authors.forename: Toshiko
authors.initials: T
authors.lastname: Nakai
authors.forename: Yuji
authors.initials: Y
authors.lastname: Kasamaki
authors.forename: Satoshi
authors.initials: S
authors.lastname: Saito
mesh_terms: D000328:Adult; D000368:Aged; D001282:Atrial Flutter / Q000503:physiopathology* / Q000601:surgery*; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D017115:Catheter Ablation; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology* / Q000601:surgery*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012008:Recurrence; D016896:Treatment Outcome; D014261:Tricuspid Valve / Q000503:physiopathology* / Q000601:surgery; D014682:Vena Cava, Inferior / Q000503:physiopathology* / Q000601:surgery