title: Pilot Study: Estimation of Stroke Volume and Cardiac Output from Pulse Wave Velocity.
abstract: BACKGROUND
  Transesophageal echocardiography (TEE) is increasingly replacing thermodilution pulmonary artery catheters to assess hemodynamics in patients at high risk for cardiovascular morbidity. However, one of the drawbacks of TEE compared to pulmonary artery catheters is the inability to measure real time stroke volume (SV) and cardiac output (CO) continuously. The aim of the present proof of concept study was to validate a novel method of SV estimation, based on pulse wave velocity (PWV) in patients undergoing cardiac surgery.
  
  
  METHODS
  This is a retrospective observational study. We measured pulse transit time by superimposing the radial arterial waveform onto the continuous wave Doppler waveform of the left ventricular outflow tract, and calculated SV (SVPWV) using the transformed Bramwell-Hill equation. The SV measured by TEE (SVTEE) was used as a reference.
  
  
  RESULTS
  A total of 190 paired SV were measured from 28 patients. A strong correlation was observed between SVPWV and SVTEE with the coefficient of determination (R2) of 0.71. A mean difference between the two (bias) was 3.70 ml with the limits of agreement ranging from -20.33 to 27.73 ml and a percentage error of 27.4% based on a Bland-Altman analysis. The concordance rate of two methods was 85.0% based on a four-quadrant plot. The angular concordance rate was 85.9% with radial limits of agreement (the radial sector that contained 95% of the data points) of ± 41.5 degrees based on a polar plot.
  
  
  CONCLUSIONS
  PWV based SV estimation yields reasonable agreement with SV measured by TEE. Further studies are required to assess its utility in different clinical situations.
authors.affiliation: Division of Cardiac Anesthesia, Department of Anesthesiology and Critical Care Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD, United States of America.
authors.forename: Yurie
authors.identifier: http://orcid.org/0000-0003-0764-3917
authors.initials: Y
authors.lastname: Obata
authors.affiliation: Department of Anesthesiology and Reanimatology, University of Fukui, Fukui, Japan.
authors.forename: Maki
authors.initials: M
authors.lastname: Mizogami
authors.affiliation: Division of Cardiac Anesthesia, Department of Anesthesiology and Critical Care Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD, United States of America.
authors.forename: Daniel
authors.initials: D
authors.lastname: Nyhan
authors.affiliation: Division of Cardiac Anesthesia, Department of Anesthesiology and Critical Care Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD, United States of America.
authors.forename: Dan E
authors.initials: DE
authors.lastname: Berkowitz
authors.affiliation: Division of Cardiac Anesthesia, Department of Anesthesiology and Critical Care Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD, United States of America.
authors.forename: Jochen
authors.initials: J
authors.lastname: Steppan
authors.affiliation: Division of Cardiac Anesthesia, Department of Anesthesiology and Critical Care Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD, United States of America.
authors.forename: Viachaslau
authors.initials: V
authors.lastname: Barodka
mesh_terms: D000368:Aged; D002302:Cardiac Output; D006348:Cardiac Surgical Procedures; D002407:Catheterization, Swan-Ganz; D017548:Echocardiography, Transesophageal; D005260:Female; D006439:Hemodynamics; D006801:Humans; D008297:Male; D008875:Middle Aged; D063177:Pulse Wave Analysis; D012189:Retrospective Studies; D013318:Stroke Volume