title: Impact of mitral isthmus anatomy on the likelihood of achieving linear block in patients undergoing catheter ablation of persistent atrial fibrillation.
abstract: BACKGROUND
  Although prior studies have described the anatomy of the mitral isthmus in patients undergoing left atrial (LA) ablation of atrial fibrillation (AF), none has examined the impact of isthmus anatomy on the likelihood of achieving conduction block.
  
  
  OBJECTIVE
  The purpose of this study was to identify morphologic characteristics of the mitral isthmus that may influence the acute efficacy of linear ablation at the mitral isthmus.
  
  
  METHODS
  Fifty-five patients (age 61 ± 10 years, 41 [75%] men, LA 46 ± 6 mm, ejection fraction 0.55 ± 0.11, AF duration 4 ± 3 years) underwent linear ablation at the mitral isthmus during an ablation procedure for persistent AF. Computed tomographic scan was performed before the procedure. The morphology of the mitral isthmus and its anatomic relationship to the adjacent vasculature were analyzed.
  
  
  RESULTS
  Complete block along the mitral isthmus was achieved in 35 (64%) of 55 patients, 23 (66%) of whom required radiofrequency ablation in the coronary sinus (CS). Patients with incomplete block were more likely to have a pouch at the isthmus (40% vs 9%; P = .01), a greater isthmus depth (8.1 ± 4.2 mm vs 5.7 ± 3.4 mm; P = .04), and a higher prevalence of an interposed circumflex artery between the CS and the mitral isthmus (60% vs 20%; P = .003) compared to patients with isthmus block. An interposed circumflex artery was the only independent predictor of incomplete conduction block at the mitral isthmus (odds ratio 4.9, 95% confidence interval 1.3-18.2; P = .02).
  
  
  CONCLUSIONS
  Preprocedural computed tomographic imaging identifies patients in whom linear ablation at the mitral isthmus is unlikely to be successful. Interposition of the circumflex artery between the mitral isthmus and the CS is associated with a lower probability of achieving complete mitral isthmus block.
authors.affiliation: Division of Cardiovascular Medicine, University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: Miki
authors.initials: M
authors.lastname: Yokokawa
authors.forename: Baskaran
authors.initials: B
authors.lastname: Sundaram
authors.forename: Anubhav
authors.initials: A
authors.lastname: Garg
authors.forename: Jadranka
authors.initials: J
authors.lastname: Stojanovska
authors.forename: Hakan
authors.initials: H
authors.lastname: Oral
authors.forename: Fred
authors.initials: F
authors.lastname: Morady
authors.forename: Aman
authors.initials: A
authors.lastname: Chugh
mesh_terms: D000328:Adult; D000368:Aged; D001281:Atrial Fibrillation / Q000503:physiopathology* / Q000601:surgery*; D017115:Catheter Ablation / Q000379:methods*; D005260:Female; D006325:Heart Atria / Q000503:physiopathology*; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D008943:Mitral Valve / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology*; D012008:Recurrence; D014057:Tomography, X-Ray Computed