title: Non-invasive flow measurement of a rotary pump ventricular assist device using quantitative contrast echocardiography.
abstract: BACKGROUND
  Many implantable ventricular assist devices (VADs) have no direct measurement of pump output. The aim of this study was to test the hypothesis that quantitative contrast echocardiography can be used to measure VAD output.
  
  
  METHODS
  Contrast-enhanced Doppler velocity-time integral (VTI) was measured in the VAD inlet and outlet cannulae. Doppler flow (Doppler Q=Doppler VTIxcannula area) was compared with measured flow (Q). A total of 130 flow measurements were made (at 6400 and 12,000 rpm).
  
  
  RESULTS
  Doppler Q in the outflow and inflow cannulae showed an excellent correlation with measured Q (outlet Doppler Q=1.0052 xQ+0.048, R2=0.9865; inlet Doppler Q=1.5043 xQ+0.003, R2=0.9904), but inlet Doppler Q was 50% higher. Correcting for the flow profile of the conical inlet tube yielded excellent correlation (inlet Doppler Q=1.0029 xQ+0.002, R2=0.9904).
  
  
  CONCLUSIONS
  Noninvasive Doppler flow techniques can be used to accurately measure VAD flow, but the flow profile in the cannula needs to be taken into account.
authors.affiliation: University of Rochester Medical Center, Rochester, New York 14642, USA. karl_schwarz@urmc.rochester.edu
authors.forename: Karl Q
authors.initials: KQ
authors.lastname: Schwarz
authors.forename: Sachin S
authors.initials: SS
authors.lastname: Parikh
authors.forename: Xucai
authors.initials: X
authors.lastname: Chen
authors.forename: David J
authors.initials: DJ
authors.lastname: Farrar
authors.forename: Sherry
authors.initials: S
authors.lastname: Steinmetz
authors.forename: Sridevi
authors.initials: S
authors.lastname: Ramamurthi
authors.forename: William
authors.initials: W
authors.lastname: Hallinan
authors.forename: H Todd
authors.initials: HT
authors.lastname: Massey
authors.forename: Leway
authors.initials: L
authors.lastname: Chen
mesh_terms: D001783:Blood Flow Velocity; D003198:Computer Simulation; D003287:Contrast Media; D003326:Coronary Circulation / Q000502:physiology*; D005240:Feasibility Studies; D006352:Heart Ventricles / Q000000981:diagnostic imaging*; D006353:Heart-Assist Devices; D006801:Humans; D008955:Models, Cardiovascular; D012212:Rheology / Q000379:methods*; D014463:Ultrasonography; D016277:Ventricular Function, Left / Q000502:physiology*; D018879:Ventricular Premature Complexes
chemical_list: D003287:Contrast Media