title: Effect of pulsatile and nonpulsatile flow on cerebral perfusion in patients with left ventricular assist devices.
abstract: BACKGROUND
  Insertion of a left ventricular assist device (LVAD) is an accepted therapy for advanced heart failure patients. However, the effects on end-organ perfusion, including cerebral autoregulation, are unclear in the presence of reduced pulsatility. Therefore, the objective of this study was to determine whether cerebral autoregulation is impaired in patients with continuous-flow (CF) LVADs.
  
  
  METHODS
  Dynamic cerebral autoregulation was assessed in both time-domain (autoregulatory index) and frequency-domain (transfer function analysis) analyses in 9 CF-LVAD subjects, 5 pulsatile LVAD subjects and 10 healthy controls, by evaluating mean arterial pressure (MAP) and cerebral blood flow velocity (CBFV) during a sit-stand maneuver at 0.05 Hz (10-second sit, 10-second stand). The autoregulatory index was calculated as the percent change in mean CBFV per mm Hg change in MAP.
  
  
  RESULTS
  The magnitude of oscillation in MAP and CBFV was greater in subjects with pulsatile LVADs than either CF-LVADs or healthy controls (p = 0.065 for MAP, p = 0.004 for CBFV). The autoregulatory index and transfer function gain were similar among groups, indicating that dynamic cerebral autoregulation is preserved among patients with CF-LVADs.
  
  
  CONCLUSIONS
  Cerebral blood flow in patients with CF-LVADs is comparable to that of healthy controls across a range of blood pressures. Patients with pulsatile devices have greater oscillations in MAP and CBFV. However, dynamic cerebral autoregulation is preserved among subjects with either type of device. Thus, the reduction in pulsatility afforded by CF-LVADs does not impair normal autoregulatory processes.
authors.affiliation: Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital, Dallas, Texas; Department of Internal Medicine, Division of Cardiology, University of Texas Southwestern Medical Center, Dallas, Texas.
authors.forename: William K
authors.initials: WK
authors.lastname: Cornwell
authors.affiliation: Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital, Dallas, Texas.
authors.forename: Takashi
authors.initials: T
authors.lastname: Tarumi
authors.affiliation: Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital, Dallas, Texas; Department of Geriatric Medicine, Radboud University, Nijmegen Medical Center, Nijmegen, The Netherlands.
authors.forename: Vincent L
authors.initials: VL
authors.lastname: Aengevaeren
authors.affiliation: Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital, Dallas, Texas.
authors.forename: Colby
authors.initials: C
authors.lastname: Ayers
authors.affiliation: Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital, Dallas, Texas.
authors.forename: Punag
authors.initials: P
authors.lastname: Divanji
authors.affiliation: Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital, Dallas, Texas.
authors.forename: Qi
authors.initials: Q
authors.lastname: Fu
authors.affiliation: Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital, Dallas, Texas.
authors.forename: Dean
authors.initials: D
authors.lastname: Palmer
authors.affiliation: Department of Internal Medicine, Division of Cardiology, University of Texas Southwestern Medical Center, Dallas, Texas.
authors.forename: Mark H
authors.initials: MH
authors.lastname: Drazner
authors.affiliation: Department of Internal Medicine, Division of Cardiology, University of Texas Southwestern Medical Center, Dallas, Texas.
authors.forename: Dan M
authors.initials: DM
authors.lastname: Meyer
authors.affiliation: Department of Internal Medicine, Division of Cardiology, University of Texas Southwestern Medical Center, Dallas, Texas.
authors.forename: Brian T
authors.initials: BT
authors.lastname: Bethea
authors.affiliation: Department of Internal Medicine, Division of Cardiology, University of Texas Southwestern Medical Center, Dallas, Texas.
authors.forename: Jeffrey L
authors.initials: JL
authors.lastname: Hastings
authors.affiliation: Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital, Dallas, Texas.
authors.forename: Naoki
authors.initials: N
authors.lastname: Fujimoto
authors.affiliation: Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital, Dallas, Texas.
authors.forename: Shigeki
authors.initials: S
authors.lastname: Shibata
authors.affiliation: Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital, Dallas, Texas; Department of Internal Medicine, Division of Cardiology, University of Texas Southwestern Medical Center, Dallas, Texas.
authors.forename: Rong
authors.initials: R
authors.lastname: Zhang
authors.affiliation: Department of Medicine, Division of Cardiology, Emory University, Atlanta, Georgia.
authors.forename: David W
authors.initials: DW
authors.lastname: Markham
authors.affiliation: Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital, Dallas, Texas; Department of Internal Medicine, Division of Cardiology, University of Texas Southwestern Medical Center, Dallas, Texas. Electronic address: benjaminlevine@texashealth.org.
authors.forename: Benjamin D
authors.initials: BD
authors.lastname: Levine
mesh_terms: D000328:Adult; D000368:Aged; D001794:Blood Pressure / Q000502:physiology; D002302:Cardiac Output / Q000502:physiology; D016022:Case-Control Studies; D002560:Cerebrovascular Circulation / Q000502:physiology*; D005260:Female; D006333:Heart Failure / Q000503:physiopathology / Q000628:therapy*; D006353:Heart-Assist Devices; D006439:Hemodynamics / Q000502:physiology; D006706:Homeostasis / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D011673:Pulsatile Flow / Q000502:physiology*; D012039:Regional Blood Flow / Q000502:physiology; D018487:Ventricular Dysfunction, Left / Q000503:physiopathology / Q000628:therapy*
keywords: LVAD; cerebral autoregulation; cerebral blood flow; nonpulsatile flow; sympathetic activity