title: Diastolic isthmus length and 'vertical' isthmus angulation identify patients with difficult catheter ablation of typical atrial flutter: a pre-procedural MRI study.
abstract: OBJECTIVE
  Catheter ablation of isthmus-dependent atrial flutter is technically demanding in some patients and extremely simple in others. The intervention targets a defined anatomical structure, the so-called cavotricuspid isthmus (CTI). We sought to characterize CTI anatomy in vivo in patients with difficult and simple catheter ablation of atrial flutter.
  
  
  RESULTS
  Twenty-six patients were studied. Seven patients with difficult (n = 6) or extremely simple (n = 1) CTI ablation procedures were retrospectively selected from our catheter ablation database. Thereafter, we prospectively studied 19 patients undergoing CTI ablation in our department. We visualized CTI anatomy by ECG- and respiration-gated free precession 1.5 T cardiac magnetic resonance imaging (MRI). Magnetic resonance imaging was analysed for systolic and diastolic CTI length, the angle between the vena cava inferior and CTI, and pouch-like recesses. These parameters were compared between patients with difficult and simple procedures, split by the median number of energy applications. Patients with difficult procedures had a longer diastolic CTI length (diastolic isthmus length 20.3 +/- 1.8 mm) than those with simple procedures (diastolic isthmus length 16.6 +/- 1.7 mm, all data as mean +/- SEM, P < 0.05). Cavotricuspid isthmus angulation with respect to inferior vena cava was closer to 90 degrees in patients with difficult procedures (deviation from 90 degrees: 15 +/- 2 degrees) than those with simple procedures (deviation 23 +/- 4 degrees, P < 0.05). Systolic CTI length was not different between groups (32 +/- 2 mm in both groups, P > 0.2).
  
  
  CONCLUSIONS
  Longer diastolic, but not systolic, CTI length and a rectangular angle between CTI and inferior vena cava render CTI catheter ablation difficult. Visualization of isthmus anatomy may help to guide difficult CTI ablation procedures.
authors.affiliation: Department of Cardiology and Angiology, Hospital of the University of Münster, Münster, Germany. kirchhp@uni-muenster.de
authors.forename: Paulus
authors.initials: P
authors.lastname: Kirchhof
authors.forename: Murat
authors.initials: M
authors.lastname: Ozgün
authors.forename: Stephan
authors.initials: S
authors.lastname: Zellerhoff
authors.forename: Gerold
authors.initials: G
authors.lastname: Mönnig
authors.forename: Lars
authors.initials: L
authors.lastname: Eckardt
authors.forename: Kristina
authors.initials: K
authors.lastname: Wasmer
authors.forename: Walter
authors.initials: W
authors.lastname: Heindel
authors.forename: Günter
authors.initials: G
authors.lastname: Breithardt
authors.forename: David
authors.initials: D
authors.lastname: Maintz
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001282:Atrial Flutter / Q000473:pathology* / Q000601:surgery*; D017115:Catheter Ablation / Q000379:methods*; D005260:Female; D006329:Heart Conduction System / Q000473:pathology* / Q000601:surgery*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011300:Preoperative Care / Q000379:methods; D025321:Surgery, Computer-Assisted / Q000379:methods*; D016896:Treatment Outcome