title: Intraoperative validation of mitral inflow determination by transesophageal echocardiography: comparison of single-plane, biplane and thermodilution techniques.
abstract: OBJECTIVE
  This study investigated the accuracy of mitral inflow quantification using biplane transesophageal echocardiography.
  
  
  BACKGROUND
  Mitral stroke volume can be reliably quantified by transthoracic Doppler echocardiography, but previous studies involving monoplane transesophageal echocardiography have yielded mixed results.
  
  
  METHODS
  Thirty patients without mitral regurgitation were prospectively examined immediately before cardiovascular surgery. Mitral annulus diameter was measured in the transverse (d1) and longitudinal views (d2) by biplane transesophageal echocardiography. Assuming an elliptic shape, the annular area was calculated as pi d1d2/4; area was also calculated from single-plane data assuming a circular annular shape as pi d2/4. The time-velocity integral of mitral annular Doppler velocity was then multiplied by annular area to yield stroke volume. These data were compared with simultaneous thermodilution measurements by linear regression.
  
  
  RESULTS
  Good correlations were observed between thermodilution (x) and Doppler (y) measurements of stroke volume (SV) (r = 0.86, p < 0.01, delta SV [y-x] = 2.64 +/- 9.86 ml for single four-chamber view; r = 0.77, p < 0.01, delta SV = 1.82 +/- 12.59 ml for two-chamber view; r = 0.94, p < 0.001, delta SV = 1.78 +/- 5.90 ml for biplane measurements) with similar data for cardiac output (r = 0.82, r = 0.74 and r = 0.92, respectively). The biplane measurements were most accurate and had less variability in individual patients (p < 0.05). This finding was supported by a numerical model that demonstrated (for an ellipse of eccentricity 1.5:1) that even maximal misalignment of biplane diameters yielded only 8% area overestimation, whereas single-plane calculations assuming a circular shape produced a variation in area of 225%.
  
  
  CONCLUSIONS
  This study validates the accuracy of measurements of mitral inflow using biplane transesophageal echocardiography with potential application for quantification of valvular regurgitation in the operating room. The results are further generalizable, indicating that orthogonal biplane measurements are both necessary and sufficient to ensure accuracy in area calculation for any elliptic structure.
authors.affiliation: Cardiovascular Imaging Center, Cleveland Clinic Foundation, Ohio 44195-5064, USA.
authors.forename: M
authors.initials: M
authors.lastname: Pu
authors.forename: B P
authors.initials: BP
authors.lastname: Griffin
authors.forename: P M
authors.initials: PM
authors.lastname: Vandervoort
authors.forename: D Y
authors.initials: DY
authors.lastname: Leung
authors.forename: D M
authors.initials: DM
authors.lastname: Cosgrove
authors.forename: J D
authors.initials: JD
authors.lastname: Thomas
mesh_terms: D000328:Adult; D000368:Aged; D002302:Cardiac Output; D006348:Cardiac Surgical Procedures; D002407:Catheterization, Swan-Ganz; D015150:Echocardiography, Doppler / Q000379:methods; D017548:Echocardiography, Transesophageal / Q000379:methods*; D005260:Female; D006801:Humans; D007430:Intraoperative Care; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D008943:Mitral Valve / Q000000981:diagnostic imaging*; D008955:Models, Cardiovascular; D008962:Models, Theoretical; D016343:Monitoring, Intraoperative; D011446:Prospective Studies; D015203:Reproducibility of Results; D013318:Stroke Volume; D013815:Thermodilution