title: Rotary pump speed modulation for generating pulsatile flow and phasic left ventricular volume unloading in a bovine model of chronic ischemic heart failure.
abstract: BACKGROUND
  Rotary blood pumps operate at a constant speed (rpm) that diminishes vascular pulsatility and variation in ventricular end-systolic and end-diastolic volumes, which may contribute to adverse events, including aortic insufficiency and gastrointestinal bleeding. In this study, pump speed modulation algorithms for generating pulsatility and variation in ventricular end-systolic and end-diastolic volumes were investigated in an ischemic heart failure (IHF) bovine model (n = 10) using a clinically implanted centrifugal-flow left ventricular assist device (LVAD).
  
  
  METHODS
  Hemodynamic and hematologic measurements were recorded during IHF baseline, constant pumps speeds, and asynchronous (19-60 cycles/min) and synchronous (copulse and counterpulse) pump speed modulation profiles using low relative pulse speed (±25%) of 3,200 ± 800 rpm and high relative pulse speed (±38%) of 2,900 ± 1,100 rpm. End-organ perfusion, hemodynamics, and pump parameters were measured to characterize pulsatility, myocardial workload, and LVAD performance for each speed modulation profile.
  
  
  RESULTS
  Speed modulation profiles augmented aortic pulse pressure, surplus hemodynamic energy, and end-organ perfusion (p < 0.01) compared with operation at constant speed. Left ventricular external work and myocardial oxygen consumption were significantly reduced compared with IHF baseline (p < 0.01) but at the expense of higher LVAD power consumption.
  
  
  CONCLUSIONS
  Pump speed modulation increases pulsatility and improves cardiac function and end-organ perfusion, but the asynchronous mode provides the technologic advantage of sensorless control. Investigation of asynchronous pump speed modulation during long-term support is warranted to test the hypothesis that operating an LVAD with speed modulation will minimize adverse events in patients supported by an LVAD that may be associated with long-term operation at a constant pump speed.
authors.affiliation: Department of Cardiovascular and Thoracic Surgery, University of Louisville, Louisville, Kentucky; Department of Bioengineering, University of Louisville, Louisville, Kentucky.
authors.forename: Kevin G
authors.initials: KG
authors.lastname: Soucy
authors.affiliation: Department of Bioengineering, University of Louisville, Louisville, Kentucky.
authors.forename: Guruprasad A
authors.initials: GA
authors.lastname: Giridharan
authors.affiliation: Department of Bioengineering, University of Louisville, Louisville, Kentucky.
authors.forename: Young
authors.initials: Y
authors.lastname: Choi
authors.affiliation: Department of Cardiovascular and Thoracic Surgery, University of Louisville, Louisville, Kentucky.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Sobieski
authors.affiliation: Department of Cardiovascular and Thoracic Surgery, University of Louisville, Louisville, Kentucky.
authors.forename: Gretel
authors.initials: G
authors.lastname: Monreal
authors.affiliation: Department of Cardiovascular and Thoracic Surgery, University of Louisville, Louisville, Kentucky.
authors.forename: Allen
authors.initials: A
authors.lastname: Cheng
authors.affiliation: Department of Cardiovascular and Thoracic Surgery, University of Louisville, Louisville, Kentucky.
authors.forename: Erin
authors.initials: E
authors.lastname: Schumer
authors.affiliation: Department of Cardiovascular and Thoracic Surgery, University of Louisville, Louisville, Kentucky.
authors.forename: Mark S
authors.initials: MS
authors.lastname: Slaughter
authors.affiliation: Department of Cardiovascular and Thoracic Surgery, University of Louisville, Louisville, Kentucky; Department of Bioengineering, University of Louisville, Louisville, Kentucky. Electronic address: steven.koenig@louisville.edu.
authors.forename: Steven C
authors.initials: SC
authors.lastname: Koenig
mesh_terms: D000818:Animals; D002306:Cardiac Volume / Q000502:physiology*; D002417:Cattle; D004195:Disease Models, Animal; D004867:Equipment Design; D006333:Heart Failure / Q000150:complications / Q000503:physiopathology / Q000628:therapy*; D006352:Heart Ventricles / Q000503:physiopathology*; D006353:Heart-Assist Devices; D008297:Male; D017202:Myocardial Ischemia / Q000150:complications / Q000503:physiopathology / Q000628:therapy*; D011673:Pulsatile Flow / Q000502:physiology*; D016277:Ventricular Function, Left / Q000502:physiology*
keywords: continuous flow; mechanical circulatory support; pulsatile flow; vascular pulsatility; ventricular assist device; ventricular volume unloading