title: Modeling left atrial volume, shape, and contraction patterns in normal subjects by cardiac magnetic resonance imaging.
abstract: BACKGROUND
  Left atrial three-dimensional shape and contraction patterns are not well described. We quantified the LA using three-dimensional cardiac MRI (CMR) in a group of normal subjects.
  
  
  METHODS
  Three-dimensional vectors were used to quantitate atrial shape and contraction using a geometric model as a three-dimensional prolate ellipsoid. Atrial area and length at end-systole and end-diastole were made in the horizontal long axis (HLA) and vertical long axis (VLA) planes. Biplane area-length products and the orthogonal LA long axis vector comprised 3 orthogonal vector lengths composed of axis measures for shape and volume calculations at end-diastole and end-systole. Vector fractional shortening in 3 dimensions was calculated for each 3-space orthogonal vector. Echocardiograms were used for comparison.
  
  
  RESULTS
  The normal LA is an oblate ellipsoid with significantly longer HLA short axis than the vertical VLA short axis (p<0.001). LA contraction in the long axis dimension is smaller than both HLA and VLA short axis dimensional changes (p<0.001). Linear correlations between LAEDV vs. LASV and LAESV vs. LAEF were highly significant.
  
  
  CONCLUSIONS
  This dimensional analysis quantitates normal left atrial shape for the first time, modeled as a prolate 3-D ellipsoid. LA contractile functions and derives mostly from contraction in the HLA and VLA short axis directions. Though LA end-diastolic volume is considered the marker of left atrial health or disease, this notion should be reconsidered in view of LA static and functional modeling in 3 dimensions.
authors.affiliation: 920 E 28th street Minneapolis, MN 55076 USA.
authors.forename: Andrew
authors.initials: A
authors.lastname: Bank
authors.forename: Kelly
authors.initials: K
authors.lastname: Wickstrom
authors.forename: Chauncy
authors.initials: C
authors.lastname: Handran
authors.forename: Daniel
authors.initials: D
authors.lastname: Burkhoff
authors.forename: John R
authors.initials: JR
authors.lastname: Lesser
authors.forename: Robert S
authors.initials: RS
authors.lastname: Schwartz
mesh_terms: D000328:Adult; D005260:Female; D006325:Heart Atria / Q000033:anatomy & histology*; D006801:Humans; D019028:Magnetic Resonance Imaging, Cine / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009200:Myocardial Contraction / Q000502:physiology*; D013318:Stroke Volume / Q000502:physiology*
keywords: Atrial model; BSA; CT; ED; EF; ES; HLA; LA; LV; Left atrium; MRI; Prolate ellipsoid; VLA; body surface area; computed tomography; ejection fraction; end-diastole; end-systole; horizontal long axis; left atrium; left ventricle; magnetic resonance imaging; vertical long axis