title: Evaluation of left atrial size on transoesophageal echocardiography: what is the best measure?
abstract: BACKGROUND
  There is no well established measurement of left atrial (LA) size on transoesophageal echocardiography (TOE). We sought to determine which measurement on TOE would best correlate with LA size obtained from transthoracic echocardiography (TTE).
  
  
  METHODS
  LA diameter (LAD) and volume (LAV) on TOE were compared to TTE measurements from 57 patients. The transthoracic examination was performed just prior to the TOE under 'similar clinical conditions'. LAD was obtained by M-mode and LAV was estimated by area-length method, M-mode derived LAD and the Simpson's method on TOE and compared to LAV estimated by the Simpson's method on transthoracic examination.
  
  
  RESULTS
  Despite LAD and LAV being underestimated on TOE, good correlations were present between LAD (r=0.85; p=0.001), area-length LAV (r=0.72; p=0.001) and Simpson's LAV (r=0.8; p=0.001). Bland Altman analysis for comparison of LAD between transoesophageal and transthoracic measurements demonstrated a mean difference of -2mm. Simpson's LAV on TOE gave the best estimation of LAV from TTE with a mean difference of -6 ml as compared to -10 ml by area-length LAV in the cohort studied.
  
  
  CONCLUSIONS
  Both left atrial diameter and volume are underestimated on TOE. The best measure with the least under-estimation of LA volume on transoesophageal examination as compared to TTE measures is obtained from Simpson's biplane estimation of LA volume.
authors.affiliation: University of Sydney, Westmead Hospital, Sydney, Australia. suzannee@westgate.wh.usyd.edu.au
authors.forename: Suzanne
authors.initials: S
authors.lastname: Eshoo
authors.forename: David L
authors.initials: DL
authors.lastname: Ross
authors.forename: Liza
authors.initials: L
authors.lastname: Thomas
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001281:Atrial Fibrillation; D001837:Body Weights and Measures / Q000379:methods*; D015331:Cohort Studies; D017548:Echocardiography, Transesophageal / Q000379:methods*; D006325:Heart Atria / Q000033:anatomy & histology*; D006801:Humans; D008875:Middle Aged; D015588:Observer Variation