title: Compression of the left atrium by the thoracic aorta in patients undergoing pulmonary vein isolation procedure for atrial fibrillation.
abstract: BACKGROUND
  With the increasing use of pre-procedural imaging techniques such as magnetic resonance imaging (MRI) and their integration with electroanatomic mapping systems in catheter ablation for atrial fibrillation (AF), atypical anatomy of the pulmonary veins (PV), left atrium (LA) and their relationship to the thoracic aorta is increasingly recognized.
  
  
  OBJECTIVE
  To characterize atypical LA-PV anatomies revealed by pre-procedural MRI and their impact on the safety and efficacy of AF ablation procedures.
  
  
  METHODS
  We reported four patients who underwent AF ablation in our electrophysiology laboratory within the last year who had atypical LA-PV anatomy due to aorta compression recognized by pre-procedural three-dimensional (3D) MRI and anatomic segmentation. Twelve matched control cases without aorta compression were selected for comparison of LA-PV measurements.
  
  
  RESULTS
  All four patients in this study had a normal-sized descending thoracic aorta that compressed the left atrium, and all patients had evidence of left inferior PV narrowing secondary to external compression. Two patients also had anterior LA compression leading to posteriorly displaced interatrial septum. Isolation was not achieved in some PVs due to anatomic restraints, concern regarding risks of aortic injury and worsening pulmonary vein stenosis. There were no immediate or short-term complications.
  
  
  CONCLUSIONS
  Extrinsic compression by the descending aorta on the LA and PV leading to LA compression and/or preexisting PV stenosis is uncommon but has potentially important implications on the overall safety and efficacy of AF ablation procedures. Pre-procedural imaging plays an important role in assessing such anatomic variations and planning of the procedures in order to minimize the risk of PV stenosis and aortic injury.
authors.affiliation: Cardiac Arrhythmia Service, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114, USA.
authors.forename: Ivan
authors.initials: I
authors.lastname: Ho
authors.forename: E Kevin
authors.initials: EK
authors.lastname: Heist
authors.forename: Arash
authors.initials: A
authors.lastname: Aryana
authors.forename: Theofanie
authors.initials: T
authors.lastname: Mela
authors.forename: Andre
authors.initials: A
authors.lastname: d'Avila
authors.forename: Jeremy
authors.initials: J
authors.lastname: Ruskin
authors.forename: Moussa
authors.initials: M
authors.lastname: Mansour
mesh_terms: D000328:Adult; D001013:Aorta, Thoracic / Q000473:pathology*; D001281:Atrial Fibrillation / Q000601:surgery*; D017115:Catheter Ablation; D005260:Female; D006325:Heart Atria / Q000473:pathology*; D006801:Humans; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D011667:Pulmonary Veins / Q000473:pathology* / Q000601:surgery*; D016896:Treatment Outcome