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Related Experiment Videos

Simulated microgravity induces microvolt T wave alternans.

S Marlene Grenon1, Xinshu Xiao, Shelley Hurwitz

  • 1Division of Endocrinology, Hypertension, and Diabetes, Brigham and Women's Hospital, Boston, and Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge 02142, USA.

Annals of Noninvasive Electrocardiology : the Official Journal of the International Society for Holter and Noninvasive Electrocardiology, Inc
|July 21, 2005
PubMed
Summary
This summary is machine-generated.

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Simulated microgravity significantly increased Microvolt T-wave alternans (MTWA), a marker for cardiac electrical instability. This suggests spaceflight may elevate the risk of dangerous heart arrhythmias.

Area of Science:

  • Cardiovascular Physiology
  • Space Medicine
  • Electrophysiology

Background:

  • Anecdotal reports link spaceflight to ventricular arrhythmias.
  • Microvolt T-wave alternans (MTWA) is a validated predictor of sudden cardiac death.
  • The effect of microgravity on cardiac electrical activity remains unclear.

Purpose of the Study:

  • To investigate if simulated microgravity increases MTWA.
  • To assess the relationship between MTWA and autonomic function during simulated microgravity.

Main Methods:

  • Twenty-four healthy males underwent 9-16 days of head-down tilt bed rest (HDTB) simulating microgravity.
  • MTWA was measured before and after HDTB during exercise stress.
  • Autonomic function, electrolytes, and catecholamines were monitored.
Keywords:
NASA Discipline CardiopulmonaryNon-NASA Center

Related Experiment Videos

Main Results:

  • MTWA positivity increased from 17% to 42% after HDTB (P=0.03).
  • Post-HDTB MTWA-positive subjects showed increased sympathetic responsiveness and norepinephrine levels.
  • A trend towards higher potassium excretion was observed after bed rest.

Conclusions:

  • Head-down tilt bed rest significantly increases MTWA, indicating simulated microgravity affects cardiac repolarization.
  • Potential contributing factors include potassium loss and altered sympathetic function.
  • This study provides initial evidence of microgravity's impact on cardiac electrical stability.