title: Central and peripheral blood flow during exercise with a continuous-flow left ventricular assist device: constant versus increasing pump speed: a pilot study.
abstract: BACKGROUND
  End-stage heart failure is associated with impaired cardiac output (CO) and organ blood flow. We determined whether CO and peripheral perfusion are maintained during exercise in patients with an axial-flow left ventricular assist device (LVAD) and whether an increase in LVAD pump speed with work rate would increase organ blood flow.
  
  
  RESULTS
  Invasively determined CO and leg blood flow and Doppler-determined cerebral perfusion were measured during 2 incremental cycle exercise tests on the same day in 8 patients provided with a HeartMate II LVAD. In random order, patients exercised both with a constant (≈9775 rpm) and with an increasing pump speed (+400 rpm per exercise stage). At 60 W, the elevation in CO was more pronounced with increased pump speed (8.7±0.6 versus 8.1±1.1 L · min(-1); mean±SD; P=0.05), but at maximal exercise increases in CO (from 7.0±0.9 to 13.6±2.5 L · min(-1); P<0.01) and leg blood flow [0.7 (0.5 to 0.8) to 4.4 (3.9 to 4.8) L · min(-1) per leg; median (range); P<0.001] were similar with both pumping modes. Normally, middle cerebral artery mean flow velocity increases from ≈50 to ≈65 cm · s(-1) during exercise, but in LVAD patients with a constant pump speed it was low at rest (39±14 cm · s(-1)) and remained unchanged during exercise, whereas in patients with increasing pump speed, it increased by 5.2±2.8 cm · s(-1) at 60 W (P<0.01).
  
  
  CONCLUSIONS
  With maximal exercise, the axial-flow LVAD supports near-normal increments in cardiac output and leg perfusion, but cerebral perfusion is poor. Increased pump speed augments cerebral perfusion during exercise.
authors.affiliation: Department of Anesthesia, The Heart Centre, Rigshospitalet, University of Copenhagen, Denmark.
authors.forename: Patrice
authors.initials: P
authors.lastname: Brassard
authors.forename: Annette S
authors.initials: AS
authors.lastname: Jensen
authors.forename: Nikolai
authors.initials: N
authors.lastname: Nordsborg
authors.forename: Finn
authors.initials: F
authors.lastname: Gustafsson
authors.forename: Jacob E
authors.initials: JE
authors.lastname: Møller
authors.forename: Christian
authors.initials: C
authors.lastname: Hassager
authors.forename: Søren
authors.initials: S
authors.lastname: Boesgaard
authors.forename: Peter Bo
authors.initials: PB
authors.lastname: Hansen
authors.forename: Peter Skov
authors.initials: PS
authors.lastname: Olsen
authors.forename: Kåre
authors.initials: K
authors.lastname: Sander
authors.forename: Niels H
authors.initials: NH
authors.lastname: Secher
authors.forename: Per Lav
authors.initials: PL
authors.lastname: Madsen
mesh_terms: D000328:Adult; D001775:Blood Circulation / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D001921:Brain / Q000098:blood supply*; D002302:Cardiac Output / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D005260:Female; D006333:Heart Failure / Q000503:physiopathology / Q000628:therapy*; D006339:Heart Rate / Q000502:physiology; D006353:Heart-Assist Devices; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D007866:Leg / Q000098:blood supply*; D008297:Male; D008875:Middle Aged; D020768:Middle Cerebral Artery / Q000502:physiology; D010865:Pilot Projects; D012039:Regional Blood Flow / Q000502:physiology*; D013997:Time Factors