Document Detail

WISE-2005: prolongation of left ventricular pre-ejection period with 56 days head-down bed rest in women.
MedLine Citation:
PMID:  20696784     Owner:  NLM     Status:  MEDLINE    
This study tested the hypothesis that prolonged physical deconditioning affects the coupling of left ventricular depolarization to its ejection (the pre-ejection period, PEPi) and that this effect is minimized by exercise countermeasures. Following assignment to non-exercise (Control) and exercise groups (Exercise), 14 females performed 56 days of continuous head-down tilt bed rest. Measurements of the electrocardiogram (ECG) and stroke volume (Doppler ultrasound) during supine rest were obtained at baseline prior to (Pre) and after (Post) the head-down tilt bed rest (HDBR) period. Compared with Pre, the PEPi was increased following head-down tilt bed rest (main effect, P < 0.005). This effect was most dominant in the Control group [Pre = 0.038 ± 0.06 s (s.d.) versus Post = 0.054 ± 0.011 s; P < 0.001]. In the Exercise group, PEPi was 0.032 ± 0.005 s Pre and 0.038 ± 0.018 s Post; P= 0.08. Neither the QRS interval nor cardiac afterload was modified by head-down tilt bed rest in Control or Exercise groups. Low-dose isoprenaline infusion reversed the head-down tilt bed rest-induced delay in the PEPi. These results suggest that head-down tilt bed rest leads to a delayed onset of systolic ejection following left ventricular depolarization in a manner that is affected little by the exercise countermeasure but is related to β-adrenergic pathways. The delayed onset of systole following head-down tilt bed rest appears to be related to mechanism(s) affecting contraction of the left ventricle rather than its depolarization.
Gary J Hodges; Louis Mattar; Kathryn A Zuj; Danielle K Greaves; Phillipe M Arbeille; Richard L Hughson; J Kevin Shoemaker
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  Experimental physiology     Volume:  95     ISSN:  1469-445X     ISO Abbreviation:  Exp. Physiol.     Publication Date:  2010 Nov 
Date Detail:
Created Date:  2010-10-22     Completed Date:  2011-01-28     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9002940     Medline TA:  Exp Physiol     Country:  England    
Other Details:
Languages:  eng     Pagination:  1081-8     Citation Subset:  IM    
School of Kinesiology, University of Western Ontario, London, Ontario, Canada.
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MeSH Terms
Bed Rest*
Blood Pressure / drug effects
Cardiovascular Deconditioning*
Head-Down Tilt / physiology*
Heart Ventricles / drug effects,  physiopathology*
Isoproterenol / diagnostic use
Lower Body Negative Pressure
Norepinephrine / diagnostic use
Stroke Volume
Supine Position
Weightlessness Countermeasures
Weightlessness Simulation
Grant Support
//Canadian Institutes of Health Research
Reg. No./Substance:
51-41-2/Norepinephrine; 7683-59-2/Isoproterenol

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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