title: The Contribution to Hemodynamics Even at Very Low Pump Speeds in the HVAD.
abstract: BACKGROUND
  We recently reported using bench testing that the Thoratec HeartMate II at 6,000 rpm contributed to hemodynamics when the heart had not recovered well, making weaning assessment questionable. In this bench study, we characterized hemodynamics and pump flow of the HeartWare HVAD at 1,800 rpm, the lowest speed commonly used to assess clinical recovery.
  
  
  METHODS
  The HVAD was operated in a mock loop at 1,800, 2,400, and 3,000 rpm. We acquired pressure-flow curves in each steady state. In pulsatile mode with the pneumatic ventricle (heart simulator) activated, pump flow, total flow, and aortic pressure (AoP) data were obtained under conditions simulating normal heart function or heart failure.
  
  
  RESULTS
  A large regurgitant flow during diastole was confirmed during normal heart function at 1,800 rpm support; however, the net flow was zero, and there was no difference in mean AoP between 1,800 rpm support and no HVAD support. In contrast, in the heart failure condition, HVAD flow at 1,800 rpm significantly contributed to mean AoP and total flow, because there was less regurgitant flow.
  
  
  CONCLUSIONS
  Similar to the results for the HeartMate II at 6,000 rpm, we found that the net pump flow generated by the HeartWare HVAD at 1,800 rpm depends on the degree of residual left ventricular (LV) function. In the setting of improved LV function, at 1,800 rpm we noted a large regurgitant flow. Although this "marker" can serve as a useful indicator for recovery, assessing recovery at this speed is flawed unless measures are taken to prevent regurgitant flow.
authors.affiliation: Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio.
authors.forename: Gengo
authors.initials: G
authors.lastname: Sunagawa
authors.affiliation: Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio.
authors.forename: Nicole
authors.initials: N
authors.lastname: Byram
authors.affiliation: Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio.
authors.forename: Jamshid H
authors.initials: JH
authors.lastname: Karimov
authors.affiliation: Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio.
authors.forename: David J
authors.initials: DJ
authors.lastname: Horvath
authors.affiliation: Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio; Department of Thoracic and Cardiovascular Surgery, Kaufman Center for Heart Failure, Cardiac Transplantation and Mechanical Circulatory Support, Miller Family Heart and Vascular Institute, Cleveland Clinic, Cleveland, Ohio.
authors.forename: Nader
authors.initials: N
authors.lastname: Moazami
authors.affiliation: Department of Cardiovascular Medicine, Kaufman Center for Heart Failure, Miller Family Heart and Vascular Institute, Cleveland Clinic, Cleveland, Ohio.
authors.forename: Randall C
authors.initials: RC
authors.lastname: Starling
authors.affiliation: Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio. Electronic address: fukamak@ccf.org.
authors.forename: Kiyotaka
authors.initials: K
authors.lastname: Fukamachi
mesh_terms: D062186:Arterial Pressure; D004867:Equipment Design; D006333:Heart Failure / Q000503:physiopathology / Q000601:surgery; D006353:Heart-Assist Devices / Q000009:adverse effects; D006439:Hemodynamics; D006801:Humans; D066298:In Vitro Techniques; D011673:Pulsatile Flow; D016277:Ventricular Function, Left