title: The feasibility of epicardial echocardiography for measuring aortic valve area by the continuity equation.
abstract: BACKGROUND
  Measuring the aortic valve area (AVA) remains an important component of a comprehensive intraoperative echocardiographic examination in patients undergoing aortic valve surgery. Epicardial echocardiography (EE) represents an accessible alternative to transesophageal echocardiography (TEE), however, its agreement and correlation with other imaging modalities for measuring AVA has not been systematically validated.
  
  
  METHODS
  EE was used in 85 patients undergoing cardiac surgery to measure AVA (AVA-EE) using the continuity equation. AVA-EE was compared to measurements obtained by intraoperative transesophageal echocardiography (AVA-TEE) in the same population. In a subset of patients, AVA-EE was also compared to AVA measurements from either preoperative transthoracic echocardiography (AVA-TTE) (n = 65) or cardiac catheterization (AVA-Cath) (n = 35) that were acquired within 4 wk before the date of surgery.
  
  
  RESULTS
  Adequate trans-AV Doppler recordings were obtained in 94% of patients for AVA-TEE and 100% of patients for AVA-EE. EE measurements of AVA showed close agreement with TEE measurements (mean difference [bias] +/- 95% CI = -0.09 cm(2) +/- 0.18 cm(2), r(2) = 0.83, P < 0.0001). AVA-EE also agreed well with AVA-Cath (mean difference +/- 95% CI = -0.03 cm(2) +/- 0.12 cm(2), r(2) = 0.87, P < 0.0001) and AVA-TTE (mean difference +/- 95% CI = -0.06 cm(2) +/- 0.22 cm(2), r(2) = 0.81, P < 0.0001).
  
  
  CONCLUSIONS
  EE measurements of AVA by the continuity equation show high agreement and closely correlate with established techniques of AVA assessment.
authors.affiliation: Department of Anesthesiology, Perioperative and Pain Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Jan N
authors.initials: JN
authors.lastname: Hilberath
authors.forename: Stanton K
authors.initials: SK
authors.lastname: Shernan
authors.forename: Scott
authors.initials: S
authors.lastname: Segal
authors.forename: Brian
authors.initials: B
authors.lastname: Smith
authors.forename: Holger K
authors.initials: HK
authors.lastname: Eltzschig
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001021:Aortic Valve / Q000000981:diagnostic imaging* / Q000601:surgery; D006328:Cardiac Catheterization; D006348:Cardiac Surgical Procedures; D015150:Echocardiography, Doppler; D017548:Echocardiography, Transesophageal; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007430:Intraoperative Care; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D015588:Observer Variation; D010496:Pericardium / Q000000981:diagnostic imaging*; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012189:Retrospective Studies