NASA Human Research Program Investigators' Workshop (2012)
4073.pdf
Impact of Microgravity and Partial Gravity on Cardiac Shape
Mohammad Kassemi*1, Ilana Iskovitz1, James Thomas2,
1
National Center for Space Exploration Research (NCSER)
NASA Glenn Research Center
Cleveland, Ohio 44135
*Corresponding Author: Mohammad.Kassemi@nasa.gov
2
Cleveland Clinic Foundation
Abstract
The impact of Microgravity on the human cardiovascular system is significant and there is
concern that long-term exposure to weightlessness can result in cardiac atrophy and arrythmia
with serious risks to the astronauts' health. One of the ways that microgravity can impact cardiac
performance is to cause a change in the sphericity of the heart. This, in turn, can
change the stress and strain distributions in the muscular structure and alter the conduction
pathways. In this paper we present a 3D finite element model of the heart based on a realistic
geometry and detailed fiber and laminate micro-architecture of the myocardium. A state-of-theart orthotropic hyperelastic material model is also adopted to account for the passive deformation
of the heart at end diastole. The material model is validated and verified against both excised
(local) and intact (global) cardiac stress strain measurements. The impact of microgravity and
partial gravity environments on the cardiac shape and the stress-strain fields in the myocardium
are assessed through parametric numerical simulations. It is shown that there is an increase in the
heart's sphericity in weightlessness. Numerical predictions are in good agreement with recent
ultrasound imaging experiments obtained during parabolic flights.Several possible implications
of these findings are discussed.