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Effect of Gravitational Gradients on Cardiac Filling and Performance.

Authors
  • Negishi, Kazuaki1
  • Borowski, Allen G2
  • Popović, Zoran B2
  • Greenberg, Neil L2
  • Martin, David S3
  • Bungo, Michael W4
  • Levine, Benjamin D5
  • Thomas, James D6
  • 1 Heart and Vascular Institute, Cleveland Clinic, Cleveland, Ohio; Menzies Research Institute Tasmania, Hobart, Australia. , (Australia)
  • 2 Heart and Vascular Institute, Cleveland Clinic, Cleveland, Ohio.
  • 3 Wyle Science, Technology, and Engineering, Cardiovascular Laboratory at the National Aeronautics and Space Administration Johnson Space Center, Houston, Texas.
  • 4 University of Texas Medical School, Houston, Texas.
  • 5 the Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas and the University of Texas Southwestern Medical Center, Dallas, Texas.
  • 6 Bluhm Cardiovascular Institute, Northwestern University, Chicago, Illinois. Electronic address: [email protected]
Type
Published Article
Journal
Journal of the American Society of Echocardiography : official publication of the American Society of Echocardiography
Publication Date
Dec 01, 2017
Volume
30
Issue
12
Pages
1180–1188
Identifiers
DOI: 10.1016/j.echo.2017.08.005
PMID: 29056408
Source
Medline
Keywords
Language
English
License
Unknown

Abstract

Gravity affects every aspect of cardiac performance. When gravitational gradients are at their greatest on Earth (i.e., during upright posture), orthostatic intolerance may ensue and is a common clinical problem that appears to be exacerbated by the adaptation to spaceflight. We sought to elucidate the alterations in cardiac performance during preload reduction with progressive upright tilt that are relevant both for space exploration and the upright posture, particularly the preload dependence of various parameters of cardiovascular performance. This was a prospective observational study with tilt-induced hydrostatic stress. Echocardiographic images were recorded at four different tilt angles in 13 astronauts, to mimic varying degrees of gravitational stress: 0° (supine, simulating microgravity of space), 22° head-up tilt (0.38 G, simulating Martian gravity), 41° (0.66 G, simulating approximate G load of a planetary lander), and 80° (1 G, effectively full Earth gravity). These images were then analyzed offline to assess the effects of preload reduction on anatomical and functional parameters. Although three-dimensional end-diastolic, end-systolic, and stroke volumes were significantly reduced during tilting, ejection fractions showed no significant change. Mitral annular e' and a' velocities were reduced with increasing gravitational load (P < .001 and P = .001), although s' was not altered. Global longitudinal strain (GLS; from -19.8% ± 2.2% to -14.7% ± 1.5%) and global circumferential strain (GCS; from -29.2% ± 2.5% to -26.0% ± 1.8%) were reduced significantly with increasing gravitational stress (both P < .001), while the change in strain rates were less certain: GLSR (P = .049); GCSR (P = .55). End-systolic elastance was not consistently changed (P = .53), while markers of cardiac afterload rose significantly (effective arterial elastance, P < .001; systemic vascular resistance, P < .001). Preload modification with gravitational loading alters most hemodynamic and echocardiographic parameters including e' velocity, GLS, and GCS. However, end-systolic elastance and strain rate appear to be more load-independent measures to examine alterations in the cardiovascular function during postural and preload changes, including microgravity. Copyright © 2017 American Society of Echocardiography. Published by Elsevier Inc. All rights reserved.

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