title: Three-dimensional anatomy of the left atrium by magnetic resonance angiography: implications for catheter ablation for atrial fibrillation.
abstract: BACKGROUND
  Pulmonary vein isolation (PVI) has become one of the primary treatments for symptomatic drug-refractory atrial fibrillation (AF). During this procedure, delivery of ablation lesions to certain regions of the left atrium can be technically challenging. Among the most challenging regions are the ridges separating the left pulmonary veins (LPV) from the left atrial appendage (LAA), and the right middle pulmonary vein (RMPV) from the right superior (RSPV) and right inferior (RIPV) pulmonary veins. A detailed anatomical characterization of these regions has not been previously reported.
  
  
  METHODS
  Magnetic resonance angiography (MRA) was performed in patients prior to undergoing PVI. Fifty consecutive patients with a RMPV identified by MRA were included in this study. Ridges associated with the left pulmonary veins were examined in an additional 30 patients who did not have a RMPV. Endoluminal views were reconstructed from the gadolinium-enhanced, breath-hold three-dimensional MRA data sets. Measurements were performed using electronic calipers.
  
  
  RESULTS
  The width of the ridge separating the LPV from the LAA was found to be 3.7 +/- 1.1 mm at its narrowest point. The segment of this ridge with a width of 5 mm or less was 16.6 +/- 6.4 mm long. The width of the ridges separating the RMPV from the RSPV and the RIPV was found to be 3.0 +/-1.5 mm and 3.1 +/-1.8 mm, respectively. There were no significant differences between LPV ridges for patients with versus without a RMPV.
  
  
  CONCLUSIONS
  The width of the ridges of atrial tissue separating LPV from the LAA and the RMPV from its neighboring veins may explain the technical challenge in obtaining stable catheter positions in these areas. A detailed assessment of the anatomy of these regions may improve the safety and efficacy of catheter ablation at these sites.
authors.affiliation: Division of Cardiology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114, USA. mmansour@partners.org
authors.forename: Moussa
authors.initials: M
authors.lastname: Mansour
authors.forename: Marwan
authors.initials: M
authors.lastname: Refaat
authors.forename: Edwin Kevin
authors.initials: EK
authors.lastname: Heist
authors.forename: Theofanie
authors.initials: T
authors.lastname: Mela
authors.forename: Ricardo
authors.initials: R
authors.lastname: Cury
authors.forename: Godtfred
authors.initials: G
authors.lastname: Holmvang
authors.forename: Jeremy N
authors.initials: JN
authors.lastname: Ruskin
mesh_terms: D001281:Atrial Fibrillation / Q000473:pathology* / Q000601:surgery*; D017115:Catheter Ablation / Q000379:methods*; D005260:Female; D006325:Heart Atria / Q000033:anatomy & histology*; D006801:Humans; D021621:Imaging, Three-Dimensional; D018810:Magnetic Resonance Angiography; D008297:Male; D008875:Middle Aged