title: Usefulness of pre-procedure cavotricuspid isthmus imaging by modified transthoracic echocardiography for predicting outcome of isthmus-dependent atrial flutter ablation.
abstract: BACKGROUND
  Anatomic characteristics of the cavotricuspid isthmus (CTI) have been reported to be related to the outcome of atrial flutter ablation therapy. However, preprocedural evaluation of CTI anatomy using modified transthoracic echocardiography to guide atrial flutter ablation has not been well described.
  
  
  METHODS
  Transthoracic echocardiography was prospectively performed before atrial flutter ablation in 42 patients with typical CTI-dependent atrial flutter. A modified apical long-axis view was designed to visualize and evaluate anatomic characteristics of the CTI and Eustachian ridge (ER). A prominent ER, extending from the inferior vena cava to the interatrial septum, is defined as an extensive ER.
  
  
  RESULTS
  Twenty-eight patients had straightforward ablation procedures, and 14 patients had difficult ablation procedures. Two patients with difficult procedures had unsuccessful ablation. Multivariate analysis (using CTI length, the presence of a pouch or recess, ER morphology, and significant tricuspid regurgitation as variables) showed that the presence of extensive ER was the only independent predictor of a difficult ablation procedure. The ablation time in patients with extensive ER (n = 13) was significantly longer than in those patients with nonextensive ER (n = 29) (1,638.4 ± 1,548.3 vs 413.8 ± 195.5 sec, P = .015). The incidence of difficulty in achieving bidirectional isthmus block was also higher in patients with extensive ER (10 of 13 vs four of 29, P < .001).
  
  
  CONCLUSIONS
  Preprocedural transthoracic echocardiography using a modified apical long-axis view is useful to characterize the morphology of the CTI and the ER. An extensive ER is a strong predictor for difficult ablation of CTI-dependent atrial flutter.
authors.affiliation: Division of Cardiology, Department of Medicine, China Medical University Hospital, Taichung, Taiwan.
authors.forename: Jan-Yow
authors.initials: JY
authors.lastname: Chen
authors.forename: Kuo-Hung
authors.initials: KH
authors.lastname: Lin
authors.forename: Ying-Ming
authors.initials: YM
authors.lastname: Liou
authors.forename: Kuan-Cheng
authors.initials: KC
authors.lastname: Chang
authors.forename: Shoei K Stephen
authors.initials: SK
authors.lastname: Huang
mesh_terms: D001282:Atrial Flutter / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000601:surgery; D017115:Catheter Ablation / Q000379:methods*; D004452:Echocardiography / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006329:Heart Conduction System / Q000000981:diagnostic imaging / Q000601:surgery*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D016896:Treatment Outcome; D014261:Tricuspid Valve / Q000000981:diagnostic imaging* / Q000294:innervation / Q000601:surgery; D014682:Vena Cava, Inferior / Q000000981:diagnostic imaging* / Q000601:surgery