title: Clinical study regarding the anatomical structures of the right atrial isthmus using intra-cardiac echocardiography: implication for catheter ablation of common atrial flutter.
abstract: BACKGROUND
  The construction of complete bi-directional block in the isthmus (ITH) between the tricuspid annulus and inferior vena cava by radiofrequency energy (RF) applications is sometimes hampered due to anatomical problems such as a thick isthmus or aneurysmal pouch in patients with common atrial flutter (AFL).
  
  
  RESULTS
  Fifteen patients were referred for RF ablation of AFL. The anatomical thickness of the right atrial ITH, diameter of the right atrium and thickness of the right atrial free wall were determined using intracardiac echocardiography (ICE), along with the endocardial electrogram recordings at the ITH. RF was applied at the ITH to create a transmural incision to treat the AFL. A significant parallel relationship between the maximum amplitude of the atrial electrogram and the thickness of the ITH, was observed. When the maximum amplitude of the atrial electrogram at the ITH exceeded 1.5 mV, the thickness at the ITH was approximately larger than 5 mm.
  
  
  CONCLUSIONS
  Using ICE, the precise measurement of the anatomical structures in the heart, including the ITH, was feasible. From the amplitude of the atrial electrogram, a deduction of the thickness at the ITH was possible, which is indispensable information for the appropriate selection of the RF devices.
authors.affiliation: Cardiac Electrophysiology Laboratory, Yokohama Red Cross Hospital, Japan. okishige@yo.rim.or.jp
authors.forename: Kaoru
authors.initials: K
authors.lastname: Okishige
authors.forename: Mihoko
authors.initials: M
authors.lastname: Kawabata
authors.forename: Kei
authors.initials: K
authors.lastname: Yamashiro
authors.forename: Chikara
authors.initials: C
authors.lastname: Ohshiro
authors.forename: Shin
authors.initials: S
authors.lastname: Umayahara
authors.forename: Masakazu
authors.initials: M
authors.lastname: Gotoh
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Sasano
authors.forename: Mitsuaki
authors.initials: M
authors.lastname: Isobe
mesh_terms: D000328:Adult; D000368:Aged; D001282:Atrial Flutter / Q000628:therapy*; D017115:Catheter Ablation; D004452:Echocardiography; D005260:Female; D006325:Heart Atria / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models; D016896:Treatment Outcome; D018084:Ultrasonography, Interventional
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