TY - JOUR
T1 - Effect of Gravitational Gradients on Cardiac Filling and Performance
AU - Negishi, Kazuaki
AU - Borowski, Allen G.
AU - Popović, Zoran B.
AU - Greenberg, Neil L.
AU - Martin, David S.
AU - Bungo, Michael W.
AU - Levine, Benjamin D.
AU - Thomas, James D.
N1 - Funding Information:
This study was funded by the National Space Biomedical Research Institute through National Aeronautics and Space Administration (NASA) cooperative Agreement NCC9-58 (to Dr. Thomas) and directly by NASA via NNJ04HH01A (to Drs. Levine and Bungo). Dr. Thomas is also supported by a grant from the Irene D. Pritzger Foundation. Dr. Negishi is supported by an award from the Select Foundation, which had no role in the preparation of this manuscript.
Publisher Copyright:
© 2017 American Society of Echocardiography
PY - 2017/12
Y1 - 2017/12
N2 - Background 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. Methods 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. Results 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). Conclusions 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.
AB - Background 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. Methods 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. Results 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). Conclusions 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.
KW - Astronauts
KW - Gravity
KW - NASA
KW - Preload, and Strain
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U2 - 10.1016/j.echo.2017.08.005
DO - 10.1016/j.echo.2017.08.005
M3 - Article
C2 - 29056408
AN - SCOPUS:85031746601
SN - 0894-7317
VL - 30
SP - 1180
EP - 1188
JO - Journal of the American Society of Echocardiography
JF - Journal of the American Society of Echocardiography
IS - 12
ER -