title: Transesophageal echocardiography during mitral valve repair underestimates mitral valve area by pressure half-time calculation.
abstract: BACKGROUND
  Mitral valve repair (MVRr) has become the mainstay of surgical treatment for mitral valvular regurgitation. Evaluation of MVRr by intraoperative transesophageal echocardiography (IOE) has been routinely employed to guide the operation. While the main objective of IOE is to assess for residual mitral regurgitation, it is also important to exclude significant mitral stenosis. Utilisation of pressure half-time (PHT) to estimate mitral valve area (MVA) has been shown to be reliable in normal clinical situations. However, in MVRr, the accuracy of MVA calculation by PHT needs to be ascertained.
  
  
  RESULTS
  Data from IOE and post-MVRr transthoracic echocardiography (TTE) from the year 1998 to 2002 were analysed and when required, offline PHT measurements were made. The mean time interval between the two echocardiographic examinations was 10.6 (1 to 56) weeks. In our 36 cases, the IOE MVA was found to be 2.1+/-0.5 cm2, with the corresponding TTE MVA to be 2.7+/-1.0 cm2. MVA by PHT with IOE underestimated TTE findings by 0.6+/-0.9 cm2 (95% CI: -0.85 to -0.24, P=0.001). In 6 patients, the IOE MVA was moderately reduced. Subsequent TTE in these patients showed that the MVA was adequate and was significantly underestimated by IOE in 5 of these patients. In all these cases, IOE underestimated MVA by a margin, which may result in a need to revise the repair.
  
  
  CONCLUSIONS
  We find that IOE immediately after MVRr tends to underestimate MVA by PHT calculation. The underestimation by IOE may have clinical importance in cases when MVA by IOE is moderately reduced. Therefore, pressure half-time measurement should not be used to assess mitral valve areas during mitral valve repair.
authors.affiliation: Cardiac Department, 5, Lower Kent Ridge Road, Level 3, Main Building, National University Hospital, 119074 Singapore. doctorpoh@yahoo.com
authors.forename: Kian-Keong
authors.initials: KK
authors.lastname: Poh
authors.forename: Eric Cho-Tek
authors.initials: EC
authors.lastname: Hong
authors.forename: Hong
authors.initials: H
authors.lastname: Yang
authors.forename: Yean-Teng
authors.initials: YT
authors.lastname: Lim
authors.forename: Tiong-Cheng
authors.initials: TC
authors.lastname: Yeo
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001837:Body Weights and Measures; D017548:Echocardiography, Transesophageal; D005260:Female; D006439:Hemodynamics; D006801:Humans; D007432:Intraoperative Period; D008297:Male; D008875:Middle Aged; D008943:Mitral Valve / Q000601:surgery*; D008944:Mitral Valve Insufficiency / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000601:surgery; D011312:Pressure