title: Cerebral hypoperfusion is exaggerated with an upright posture in heart failure: impact of depressed cardiac output.
abstract: OBJECTIVE
  The purpose of this study was to examine cerebral blood flow (CBF) supine and during upright sitting in HF patients and control subjects to test the hypothesis that patients with HF will have a greater reduction in CBF from supine to seated compared with the control group.
  
  
  BACKGROUND
  Reduced CBF has been reported in patients with heart failure (HF). However, previous work has only examined CBF while supine, although an upright posture common to daily living may lead to further reductions.
  
  
  METHODS
  In 22 HF patients and 22 age- and sex-matched control subjects, continuous heart rate, mean arterial pressure, and end-tidal carbon dioxide readings were collected while supine and seated upright. Cardiac output was estimated from pulse contour analysis and was corrected for body size (cardiac index). The right internal carotid artery was imaged by using ultrasound to estimate CBF.
  
  
  RESULTS
  Heart rate increased less in response to the upright posture in HF patients versus control subjects (p = 0.006). Mean arterial pressure was unchanged, whereas end-tidal carbon dioxide decreased in response to position (p = 0.004) but did not differ between groups. Cardiac index was lower in patients with HF (p < 0.001) and decreased in both groups in response to the upright posture (p = 0.025), with a trend for a greater decrease in the HF group (p = 0.065). CBF decreased more in response to the upright posture in the HF group than in the control group (p = 0.007).
  
  
  CONCLUSIONS
  The reduction in CBF was exaggerated in the upright posture in HF patients and may increase the risk for subsequent cognitive impairment.
authors.affiliation: Schlegel-University of Waterloo Research Institute for Aging, Faculty of Applied Health Sciences, Waterloo, Ontario, Canada.
authors.forename: Katelyn S
authors.initials: KS
authors.lastname: Fraser
authors.affiliation: Schlegel-University of Waterloo Research Institute for Aging, Faculty of Applied Health Sciences, Waterloo, Ontario, Canada.
authors.forename: George A
authors.initials: GA
authors.lastname: Heckman
authors.affiliation: McMaster University and Hamilton Health Sciences, Hamilton, Ontario, Canada.
authors.forename: Robert S
authors.initials: RS
authors.lastname: McKelvie
authors.affiliation: McMaster University and Hamilton Health Sciences, Hamilton, Ontario, Canada.
authors.forename: Karen
authors.initials: K
authors.lastname: Harkness
authors.affiliation: Schlegel-University of Waterloo Research Institute for Aging, Faculty of Applied Health Sciences, Waterloo, Ontario, Canada.
authors.forename: Laura E
authors.initials: LE
authors.lastname: Middleton
authors.affiliation: Schlegel-University of Waterloo Research Institute for Aging, Faculty of Applied Health Sciences, Waterloo, Ontario, Canada. Electronic address: hughson@uwaterloo.ca.
authors.forename: Richard L
authors.initials: RL
authors.lastname: Hughson
mesh_terms: D000368:Aged; D002245:Carbon Dioxide / Q000378:metabolism; D002303:Cardiac Output, Low / Q000503:physiopathology*; D016022:Case-Control Studies; D002560:Cerebrovascular Circulation / Q000502:physiology*; D005260:Female; D006333:Heart Failure / Q000503:physiopathology*; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D011187:Posture / Q000502:physiology
chemical_list: D002245:Carbon Dioxide
keywords: cardiac output; cerebral blood flow; heart failure; posture