Document Detail

Diastolic suction is impaired by bed rest: MRI tagging studies of diastolic untwisting.
MedLine Citation:
PMID:  18239079     Owner:  NLM     Status:  MEDLINE    
Bed rest deconditioning leads to physiological cardiac atrophy, which may compromise left ventricular (LV) filling during orthostatic stress by reducing diastolic untwisting and suction. To test this hypothesis, myocardial-tagged magnetic resonance imaging (MRI) was performed, and maximal untwisting rates of the endocardium, midwall, and epicardium were calculated by Harmonic Phase Analysis (HARP) before and after -6 degrees head-down tilt bed rest for 18 days with (n = 14) and without exercise training (n = 10). LV mass and LV end-diastolic volume were measured using cine MRI. Exercise subjects cycled on a supine ergometer for 30 min, three times per day at 75% maximal heart rate (HR). After sedentary bed rest, there was a significant reduction in maximal untwisting rates of the midwall (-46.8 +/- 14.3 to -35.4 +/- 12.4 degrees /s; P = 0.04) where untwisting is most reliably measured, and to a lesser degree of certainty in the endocardium (-50.3 +/- 13.8 to -40.1 +/- 18.5 degrees /s; P = 0.09); the epicardium was unchanged. In contrast, when exercise was performed in bed, untwisting rates were enhanced at the endocardium (-48.4 +/- 20.8 to -72.3 +/- 22.3 degrees /ms; P = 0.05) and midwall (-39.2 +/- 12.2 to -59.0 +/- 19.6 degrees /s; P = 0.03). The differential response was significant between groups at the endocardium (interaction P = 0.02) and the midwall (interaction P = 0.004). LV mass decreased in the sedentary group (156.4 +/- 30.3 to 149.5 +/- 27.9 g; P = 0.07), but it increased slightly in the exercise-trained subjects (156.4 +/- 34.3 to 162.3 +/- 40.5 g; P = 0.16); (interaction P = 0.03). We conclude that diastolic untwisting is impaired following sedentary bed rest. However, exercise training in bed can prevent the physiological cardiac remodeling associated with bed rest and preserve or even enhance diastolic suction.
Todd A Dorfman; Boaz D Rosen; Merja A Perhonen; Tommy Tillery; Roddy McColl; Ronald M Peshock; Benjamin D Levine
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, U.S. Gov't, Non-P.H.S.     Date:  2008-01-31
Journal Detail:
Title:  Journal of applied physiology (Bethesda, Md. : 1985)     Volume:  104     ISSN:  8750-7587     ISO Abbreviation:  J. Appl. Physiol.     Publication Date:  2008 Apr 
Date Detail:
Created Date:  2008-04-03     Completed Date:  2008-06-17     Revised Date:  2013-09-26    
Medline Journal Info:
Nlm Unique ID:  8502536     Medline TA:  J Appl Physiol (1985)     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1037-44     Citation Subset:  IM    
Institute for Exercise and Environmental Medicine, 7232 Greenville Ave., Suite 435, Dallas, TX 75231, USA.
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MeSH Terms
Bed Rest / adverse effects*
Endocardium / physiology
Heart / anatomy & histology,  physiology*
Image Processing, Computer-Assisted
Magnetic Resonance Imaging
Middle Aged
Mitral Valve / physiology
Pericardium / physiology
Physical Fitness / physiology
Plasma Volume / physiology
Space Flight
Grant Support

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

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