title: Impact of left ventricular assist device speed adjustment on exercise tolerance and markers of wall stress.
abstract: BACKGROUND
  Left ventricular assist devices are crucial in rehabilitation of patients with end-stage heart failure. Whether cardiopulmonary function is enhanced with higher pump output is unknown.
  
  
  METHODS
  10 patients (aged 39±16 years, mean±SD) underwent monitored adjustment of pump speed to determine minimum safe low speed and maximum safe high speed at rest. Patients were then randomized to these speed settings and underwent three 6-minute walk tests (6MWT) and symptom-limited cardiopulmonary stress tests (CPX) on separate days.
  
  
  RESULTS
  Pump speed settings (low, normal and high) resulted in significantly different resting pump flows of 4.43±0.6, 5.03±0.94, and 5.72±1.2 l/min (P<.001). There was a significant enhancement of pump flows (greater at higher speed settings) with exercise (P<0.05). Increased pump speed was associated with a trend to increased 6MWT distance (P=.10); and CPX exercise time (p=.27). Maximum workload achieved and peak oxygen consumption were significantly different comparing low to high pump speed settings only (P<.05). N-terminal-pro-B-type natriuretic peptide release was significantly reduced at higher pump speed with exercise (P<.01).
  
  
  CONCLUSIONS
  We have found that alteration of pump speed setting resulted in significant variation in estimated pump flow. The high-speed setting was associated with lower natriuretic hormone release consistent with lower myocardial wall stress. This did not, however, improve exercise tolerance.
authors.affiliation: St. Vincent's Hospital, Sydney - Australia.|Victor Chang Cardiac Research Institute, Sydney - Australia.
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Hayward
authors.affiliation: The Alfred Hospital, Melbourne - Australia.
authors.forename: Robert
authors.initials: R
authors.lastname: Salamonsen
authors.affiliation: St. Vincent's Hospital, Sydney - Australia.|Victor Chang Cardiac Research Institute, Sydney - Australia.
authors.forename: Anne M
authors.initials: AM
authors.lastname: Keogh
authors.affiliation: Berlin Heart, Berlin - Germany.
authors.forename: John
authors.initials: J
authors.lastname: Woodard
authors.affiliation: Thorvascular Pty Ltd, Crows Nest, Sydney - Australia.
authors.forename: Peter
authors.initials: P
authors.lastname: Ayre
authors.affiliation: St. Vincent's Hospital, Sydney - Australia.
authors.forename: Roslyn
authors.initials: R
authors.lastname: Prichard
authors.affiliation: St. Vincent's Hospital, Sydney - Australia.
authors.forename: Eugene
authors.initials: E
authors.lastname: Kotlyar
authors.affiliation: St. Vincent's Hospital, Sydney - Australia.|Victor Chang Cardiac Research Institute, Sydney - Australia.
authors.forename: Peter S
authors.initials: PS
authors.lastname: Macdonald
authors.affiliation: St. Vincent's Hospital, Sydney - Australia.
authors.forename: Paul
authors.initials: P
authors.lastname: Jansz
authors.affiliation: St. Vincent's Hospital, Sydney - Australia.
authors.forename: Phillip
authors.initials: P
authors.lastname: Spratt
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000097:blood; D001794:Blood Pressure; D002245:Carbon Dioxide / Q000378:metabolism; D005080:Exercise Test; D017079:Exercise Tolerance; D005260:Female; D006353:Heart-Assist Devices; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D008297:Male; D008875:Middle Aged; D020097:Natriuretic Peptide, Brain / Q000097:blood; D010101:Oxygen Consumption; D010446:Peptide Fragments / Q000097:blood; D012123:Pulmonary Ventilation; D055815:Young Adult
chemical_list: D015415:Biomarkers; D010446:Peptide Fragments; C109794:pro-brain natriuretic peptide (1-76); D020097:Natriuretic Peptide, Brain; D002245:Carbon Dioxide; D019344:Lactic Acid