title: Role of the right atrial substrate in different types of atrial arrhythmias.
abstract: BACKGROUND
  The regional distribution of the low-voltage zones (LVZs) may relate to the maintenance of atrial arrhythmias in the right atrium (RA).
  
  
  OBJECTIVE
  The purpose of this study was to investigate the RA substrate characteristics in different types of atrial arrhythmias originating from RA and left atrium (LA).
  
  
  METHODS
  Forty-five patients (35 men, age = 62 +/- 15 years) with RA atypical atrial flutter (n = 15, group 1), RA atrial fibrillation (AF; n = 15, no PV initiating foci, group 2), and LA AF (n = 1 5, no RA arrhythmias, group 3) referred for three-dimensional EnSite mapping were included. Voltage and activation maps were visualized.
  
  
  RESULTS
  The mean voltage of the RA was lower in group 2, and compared with group 3, a voltage reduction during atrial pacing was evident in groups 1 and 2. The fixed LVZs (independent of the rhythm) were mostly located along the lower crista terminalis (CT). A functional extension of the LVZ was located on the CT in 84% of patients, sinus venosa in 18%, and free-wall region in 27%, forming the borders of the slow conduction isthmus for the reentrant circuits. The number of slow conduction isthmuses was 1.3 +/- 0.9, 2.2 +/- 1.0, and 0.87 +/- 0.74, for the groups 1-3 patients, respectively (P <.05). Radiofrequency ablation connecting the LVZs successfully eliminated those isthmuses. The long-term follow-up revealed that 66% of the patients remained in sinus rhythm.
  
  
  CONCLUSIONS
  Single and multiple slow conduction isthmuses bordered by the fixed and functional LVZs were critical for the reentrant circuits in the RA. The conduction isthmuses could be identified by their substrate characteristics and ablated successfully.
authors.affiliation: Division of Cardiology, Department of Medicine, Taipei Veterans General Hospital, Taipei, Taiwan.
authors.forename: Yenn-Jiang
authors.initials: YJ
authors.lastname: Lin
authors.forename: Satoshi
authors.initials: S
authors.lastname: Higa
authors.forename: Ching-Tai
authors.initials: CT
authors.lastname: Tai
authors.forename: Shih-Lin
authors.initials: SL
authors.lastname: Chang
authors.forename: Kun-Tai
authors.initials: KT
authors.lastname: Lee
authors.forename: Li-Wei
authors.initials: LW
authors.lastname: Lo
authors.forename: Sugako
authors.initials: S
authors.lastname: Ishigaki
authors.forename: Ta-Chuan
authors.initials: TC
authors.lastname: Tuan
authors.forename: Wanwarang
authors.initials: W
authors.lastname: Wongcharoen
authors.forename: Yu-Feng
authors.initials: YF
authors.lastname: Hu
authors.forename: Min-Hsiung
authors.initials: MH
authors.lastname: Hsieh
authors.forename: Hsuan-Ming
authors.initials: HM
authors.lastname: Tsao
authors.forename: Shih-Ann
authors.initials: SA
authors.lastname: Chen
mesh_terms: D001281:Atrial Fibrillation / Q000145:classification / Q000503:physiopathology* / Q000601:surgery; D001282:Atrial Flutter / Q000145:classification / Q000503:physiopathology* / Q000601:surgery; D018780:Body Surface Potential Mapping; D017115:Catheter Ablation / Q000379:methods; D022062:Electrophysiologic Techniques, Cardiac; D005260:Female; D005500:Follow-Up Studies; D006325:Heart Atria / Q000294:innervation / Q000503:physiopathology*; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011379:Prognosis