title: High-resolution mapping around the eustachian ridge during typical atrial flutter.
abstract: BACKGROUND
  Although the reentrant circuit of typical atrial flutter (AFL) has been well recognized, the activation around the Eustachian ridge (ER) has not been fully characterized. The aim of this study was to delineate the activation patterns around the ER during typical AFL using high-resolution noncontact mapping.
  
  
  METHODS
  Fifty-three patients (M/F = 43/10, 62 +/- 14 years) with typical AFL were included. The high-resolution mapping of the right atrium using a noncontact mapping system during AFL and pacing from the coronary sinus (CS) was performed to evaluate the conduction through the ER.
  
  
  RESULTS
  Three types of activation patterns around the ER could be classified according to the ER conduction during AFL and CS pacing. Type I (n = 21, M/F = 16/5, 61 +/- 13 years) exhibited conduction block at the ER during AFL and CS pacing. The local unipolar electrograms at the ER exhibited long double potentials (DPs) (109 +/- 12 ms, range 77-153 ms) during AFL and CS pacing (84 +/- 18 ms, range 48-129 ms). Type II (n = 8, M/F = 7/1, 61 +/- 15 years) exhibited conduction block at the ER during AFL, but conduction through the ER during CS pacing. The unipolar electrograms exhibited long DPs (119 +/- 12 ms, range 97-141 ms) at the ER during the tachycardia and an rS pattern during CS pacing. Type III (n = 24, M/F = 20/4, 61 +/- 16 years) exhibited an activation wavefront that passed along the ER, with the sinus venosa as the posterior barrier during AFL. During CS pacing, all cases exhibited conduction through the ER with an rS pattern.
  
  
  CONCLUSIONS
  This study is the first to demonstrate the three patterns of activation along the ER during AFL and CS pacing. This finding suggested that the ER is an anatomic and functional barrier during typical AFL.
authors.affiliation: Heart Failure Division, Cardiovascular Center, Taichung Veterans General Hospital, Taipei, Taiwan.
authors.forename: Jin-Long
authors.initials: JL
authors.lastname: Huang
authors.forename: Ching-Tai
authors.initials: CT
authors.lastname: Tai
authors.forename: Tu-Ying
authors.initials: TY
authors.lastname: Liu
authors.forename: Yenn-Jiang
authors.initials: YJ
authors.lastname: Lin
authors.forename: Pi-Chang
authors.initials: PC
authors.lastname: Lee
authors.forename: Chih-Tai
authors.initials: CT
authors.lastname: Ting
authors.forename: Shih-Ann
authors.initials: SA
authors.lastname: Chen
mesh_terms: D000368:Aged; D001282:Atrial Flutter / Q000175:diagnosis* / Q000503:physiopathology*; D018780:Body Surface Potential Mapping / Q000379:methods*; D006328:Cardiac Catheterization / Q000379:methods; D022062:Electrophysiologic Techniques, Cardiac / Q000379:methods; D005260:Female; D006325:Heart Atria; D006329:Heart Conduction System / Q000502:physiology; D006346:Heart Septum / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged