title: Tachycardia circuit in typical atrial flutter: the role of a posterolateral line of block in the perpetuation of the tachycardia.
abstract: BACKGROUND
  The essential boundaries in typical atrial flutter (AF) are unknown.
  
  
  METHODS
  To examine the role of the tricuspid annulus (TA) and posterolateral line of block (LB) in maintaining AF, single extrastimuli were delivered during AF both around the LB and the TA in 29 patients. Single extrastimuli were delivered from the superior, middle, and inferior third of the anterior LB, superior, middle, and inferior third of the posterior LB, and the superior, lateral, inferior, and septal portions of the TA. The longest coupling interval (LCI) of single extrastimuli that reset AF and subsequent return cycle (RC) were analyzed.
  
  
  RESULTS
  The resetting response showed two patterns (groups 1 and 2). The differences between the AF cycle length (AFCL) and the LCI (AFCL-LCI) at the superior, lateral, inferior, and septal portions of the TA were the shortest, and were significantly shorter than those at the other sites (P < 0.0001) in group 1. However, the AFCL-LCI at the superior, middle, and inferior third of the anterior LB, and the superior, lateral, inferior, and septal portions of the TA were the shortest, and were significantly shorter than those at the other sites (P < 0.0001) in group 2. The difference between the RC and the AFCL exhibited the same two patterns, similar to the AFCL-LCI. In group 1, a single extrastimulus produced an artificial conduction across the LB, but AF was not reset.
  
  
  CONCLUSIONS
  Two types of reentry circuits exist in AF; one has its essential reentry circuit confined to the TA and thus the LB acts as a bystander, while the LB and the TA are essential boundaries in the other one.
authors: Department of Cardiovascular Medicine, Graduate School of Medical Sciences, Kumamoto University, Kumamoto, Japan.
authors: Hiroshige
authors: H
authors: Yamabe
authors: Yasuaki
authors: Y
authors: Tanaka
authors: Kenji
authors: K
authors: Morihisa
authors: Takashi
authors: T
authors: Uemura
authors: Hiroaki
authors: H
authors: Kawano
authors: Yasuhiro
authors: Y
authors: Nagayoshi
authors: Sunao
authors: S
authors: Kojima
authors: Hisao
authors: H
authors: Ogawa
mesh_terms: D001281:Atrial Fibrillation / Q000150:complications* / Q000503:physiopathology*; D018780:Body Surface Potential Mapping; D005260:Female; D006327:Heart Block / Q000150:complications* / Q000503:physiopathology*; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009407:Nerve Block / Q000379:methods; D013610:Tachycardia / Q000209:etiology* / Q000503:physiopathology*