title: Identification of extremely slow conduction in the cavotricuspid isthmus during common atrial flutter ablation.
abstract: BACKGROUND
  Complete isthmus block has been used as an endpoint for radiofrequency ablation for common atrial flutter (AF). We sought to systematically evaluate extremely slow conduction (ESC), which is easily misinterpreted as complete block.
  
  
  RESULTS
  We studied 107 consecutive patients (92 men, 15 women, 58 +/- 11 years) who had undergone a successful AF ablation procedure. A 24-pole catheter was positioned along the tricuspid annulus spanning the isthmus. Complete isthmus block was defined as the presence of a complete corridor of double potentials along the ablation line. Activation delay time (AT), activation difference (deltaA) between two adjacent dipoles, maximum activation difference (deltaA(max)), change in polarity (CP) and change in amplitude (CA) of the bipolar atrial electrogram were recorded and P-wave morphology in the surface electrocardiogram was analyzed. ESC was observed in 16 patients. Between ESC and complete block, differences were found on the two lateral dipoles adjacent to the ablation line (AT: 148 +/- 17 vs. 183 +/- 27 ms and 155 +/- 18 vs. 170 +/- 28 ms, P < 0.01; deltaA: -91 +/- 22 vs. -126 +/- 28 ms and -7 +/- 13 vs. 13 +/- 6 ms, P < 0.01). Statistically significant differences in CP were detected on the relevant dipoles (7/16 vs. 14/16 and 6/16 vs.13/16, P < 0.05). No significant difference was found either in CA or in terminal P wave positivity. Mean deltaA(max) were 13.8 +/- 5.0 and 27.8 +/- 9.5 ms (P < 0.001) respectively in ESC and complete block. Two types of ESC, regular and irregular, were demonstrated during the ablation procedure.
  
  
  CONCLUSIONS
  (1) ESC was observed in 15% of the patients during the AF ablation procedure. (2) The parameters of AT, deltaA, and CP may help to differentiate ESC from complete block. DeltaA(max) might be the most powerful indicator. (3) To verify complete block, it is essential to position the mapping catheter across the CTI in order to demonstrate the activation sequence up to the ablation line.
authors.affiliation: Department of Heart Disease, Haukeland University Hospital, Bergen, Norway. jian.chen@med.uib.no
authors.forename: Jian
authors.initials: J
authors.lastname: Chen
authors.forename: Christian
authors.initials: C
authors.lastname: de Chillou
authors.forename: Per Ivar
authors.initials: PI
authors.lastname: Hoff
authors.forename: Ole
authors.initials: O
authors.lastname: Rossvoll
authors.forename: Marius
authors.initials: M
authors.lastname: Andronache
authors.forename: Nicolas
authors.initials: N
authors.lastname: Sadoul
authors.forename: Isabelle
authors.initials: I
authors.lastname: Magnin-Poull
authors.forename: Knut Ståle
authors.initials: KS
authors.lastname: Erga
authors.forename: Etienne
authors.initials: E
authors.lastname: Aliot
authors.forename: Ole-Jørgen
authors.initials: OJ
authors.lastname: Ohm
mesh_terms: D000368:Aged; D000465:Algorithms; D001282:Atrial Flutter / Q000150:complications / Q000175:diagnosis* / Q000503:physiopathology* / Q000601:surgery; D017115:Catheter Ablation / Q000379:methods*; D022062:Electrophysiologic Techniques, Cardiac / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006327:Heart Block / Q000150:complications / Q000175:diagnosis* / Q000503:physiopathology* / Q000601:surgery; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D013997:Time Factors; D014261:Tricuspid Valve / Q000503:physiopathology*; D014684:Venae Cavae / Q000503:physiopathology*