title: A novel operator-independent algorithm for cardiac output measurements based on three-dimensional transoesophageal colour Doppler echocardiography.
abstract: OBJECTIVE
  Cardiac output (CO) measurements from three-dimensional (3D) trans-mitral Doppler echocardiography are prone to error as manual selection of the region of interest (i.e. the site of measurement) is required. We newly developed an automated, user-independent algorithm to select the site of colour Doppler CO measurement. We aimed to validate this new method by benchmarking it against thermodilution, the current gold standard for CO measurements.
  
  
  RESULTS
  Transoesophageal colour 3D Doppler echocardiographic studies were obtained from 15 patients who also had received a pulmonary catheter for invasive CO measurements. Trans-mitral flow was determined using a novel operator-independent algorithm to automatically select the optimal site of measurement. The operator-independent CO measurements were referenced against thermodilution. A good correlation was found between operator-independent Doppler flow computations and thermodilution with a mean bias of 0.09 L/min, standard deviation of bias 1.3 L/min, and a 26% error (2 SD/mean CO). Mean CO was 4.94 L/min (range 3.10-7.10 L/min).
  
  
  CONCLUSIONS
  Our findings demonstrate that CO computation from transoesophageal colour 3D Doppler echo can be automated concerning the site of velocity measurement. Our operator-independent algorithm provides an objective and reproducible alternative to thermodilution.
authors.affiliation: Surgical Planning Lab, Brigham and Women's Hospital, 75 Francis Street, Boston, MA 02115, USA. matthews@bwh.harvard.edu
authors.forename: Felix
authors.initials: F
authors.lastname: Matthews
authors.forename: Thomas
authors.initials: T
authors.lastname: Largiadèr
authors.forename: Patricia
authors.initials: P
authors.lastname: Rhomberg
authors.forename: Bernd
authors.initials: B
authors.lastname: van der Loo
authors.forename: Edith R
authors.initials: ER
authors.lastname: Schmid
authors.forename: Rolf
authors.initials: R
authors.lastname: Jenni
mesh_terms: D000368:Aged; D000465:Algorithms; D019985:Benchmarking; D002302:Cardiac Output; D016001:Confidence Intervals; D004452:Echocardiography; D018618:Echocardiography, Doppler, Color; D019560:Echocardiography, Three-Dimensional; D005260:Female; D006352:Heart Ventricles / Q000000981:diagnostic imaging* / Q000473:pathology; D006801:Humans; D016014:Linear Models; D008297:Male; D013223:Statistics as Topic; D013815:Thermodilution