title: Use of computed tomography to identify atrial fibrillation associated differences in left atrial wall thickness and density.
abstract: BACKGROUND
  Left atrial (LA) tissue characteristics may play an important role in atrial fibrillation (AF) induction and perpetuation. Although frequently used in clinical practice, computed tomography (CT) has not been employed to describe differences in LA wall properties between AF patients and controls. We sought to noninvasively characterize AF-associated differences in LA tissue using CT.
  
  
  METHODS
  CT images of the LA were obtained in 98 consecutive patients undergoing AF ablation and in 89 controls. A custom software algorithm was used to measure wall thickness and density in four prespecified regions of the LA.
  
  
  RESULTS
  On average, LA walls were thinner (-15.5%, 95% confidence interval [CI] -23.2 to -7.8%, P < 0.001) and demonstrated significantly lower density (-19.7 Hounsfield Units [HU], 95% CI -27.0 to -12.5 HU, P < 0.001) in AF patients compared to controls. In linear mixed models adjusting for demographics, clinical variables, and other CT measurements, the average LA, interatrial septum, LA appendage, and anterior walls remained significantly thinner in AF patients. After adjusting for the same potential confounders, history of AF was associated with reduced density in the LA anterior wall and increased density below the right inferior pulmonary vein and in the LA appendage.
  
  
  CONCLUSIONS
  Application of an automated measurement algorithm to CT imaging of the atrium identified significant thinning of the LA wall and regional alterations in tissue density in patients with a history of AF. These findings suggest differences in LA tissue composition can be noninvasively identified and quantified using CT.
authors.affiliation: Division of Cardiology, University of California, San Francisco, CA, USA.
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Dewland
authors.forename: Max
authors.initials: M
authors.lastname: Wintermark
authors.forename: Anna
authors.initials: A
authors.lastname: Vaysman
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Smith
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Tong
authors.forename: Eric
authors.initials: E
authors.lastname: Vittinghoff
authors.forename: Gregory M
authors.initials: GM
authors.lastname: Marcus
mesh_terms: D000368:Aged; D000465:Algorithms; D001281:Atrial Fibrillation / Q000000981:diagnostic imaging*; D005260:Female; D006325:Heart Atria / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*