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Computer systems analysis of spaceflight induced changes in left ventricular mass.
Richard L Summers1, David S Martin, Janice V Meck
1Department of Emergency Medicine, University of Mississippi Medical Center, Jackson, Mississippi 39216, USA. rsummers@pol.net
Computers in Biology and Medicine
|July 1, 2006
Summary
Space travel causes cardiovascular deconditioning, potentially due to reduced left ventricular mass (LVM). This study suggests LVM changes after spaceflight are due to fluid shifts, not muscle atrophy, with recovery within days.
Area of Science:
- Cardiovascular Physiology
- Space Medicine
- Systems Biology
Background:
- Space travel causes circulatory adaptations, including postflight orthostasis.
- Reduced left ventricular mass (LVM) after microgravity is a suspected cause of cardiovascular deconditioning.
- The precise physiological mechanism for myocardial changes during spaceflight remains unclear.
Purpose of the Study:
- To investigate sequential alterations in echocardiographic LVM from preflight to postflight recovery.
- To evaluate the role of fluid shifts versus cardiac atrophy in microgravity-induced LVM changes.
- To utilize systems analysis and computer modeling to understand cardiovascular responses to spaceflight.
Main Methods:
- Echocardiographic measurement of LVM in astronauts preflight, post-landing, and 3 days into recovery.
- Systems analysis using an advanced computer model of circulatory function.
- Comparison with ground-based studies inducing hypovolemia via dehydration.
Main Results:
- A 9.1% reduction in postflight LVM was observed, returning to preflight values by day 3.
- Computer model simulations indicated LVM reduction is explained by fluid shifts and plasma volume loss.
- Ground-based dehydration studies showed reduced plasma volume correlated with LVM reduction.
Conclusions:
- Microgravity-induced reductions in LVM appear to be secondary to fluid exchanges, not cardiac muscle atrophy.
- Physiological fluid shifts are a likely mechanism for observed LVM changes after spaceflight.
- These LVM changes are reversible within days of returning to Earth's gravity.