title: Unidirectional conduction block at cavotricuspid isthmus created by radiofrequency catheter ablation in patients with typical atrial flutter.
abstract: BACKGROUND
  Although unidirectional conduction block at the cavotricuspid isthmus can be created by radiofrequency ablation for atrial flutter, its underlying mechanism has not been elucidated.
  
  
  RESULTS
  Twenty-seven patients (22 men and 5 women; mean age 59 +/- 11 years) who met the following criteria were studied: (1) bidirectional isthmus conduction demonstrable at baseline; (2) at least one linear lesion attempted on the cavotricuspid isthmus with radiofrequency catheter ablation; and (3) conduction times at anterolateral and posteromedial portions of the isthmus measured for both clockwise and counterclockwise directions before the ablation procedure. Unidirectional conduction block was observed before achieving bidirectional block in 9 patients (group I); the remaining 18 patients did not exhibit unidirectional conduction block (group II). All unidirectional conduction blocks were demonstrated in the counterclockwise direction. Anterolateral isthmus conduction time in group I was significantly longer than that in group II in both directions. However, there were no significant differences in posteromedial isthmus conduction time between groups I and II in either direction. Anterolateral isthmus conduction time was significantly longer than posteromedial conduction time in group I but not in group II.
  
  
  CONCLUSIONS
  There were significant differences in conduction properties at the cavotricuspid isthmus between patients who developed unidirectional conduction block and those who did not. Our results support the notion that anisotropy contributes to the genesis of unidirectional conduction block at the cavotricuspid isthmus during the radiofrequency ablation procedure.
authors.affiliation: Cardiac Electrophysiology & Arrhythmia Service, Stanford University Medical Center, Stanford, California, USA. t-matsu@m2.kufm.kagoshima-u.ac.jp
authors.forename: Takehiko
authors.initials: T
authors.lastname: Matsushita
authors.forename: Sung
authors.initials: S
authors.lastname: Chun
authors.forename: L Bing
authors.initials: LB
authors.lastname: Liem
authors.forename: Karen J
authors.initials: KJ
authors.lastname: Friday
authors.forename: Ruey J
authors.initials: RJ
authors.lastname: Sung
mesh_terms: D000368:Aged; D001282:Atrial Flutter / Q000503:physiopathology* / Q000601:surgery*; D017115:Catheter Ablation; D005260:Female; D006324:Heart Arrest, Induced; 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