Long-Term Microgravity Exposure Increases ECG Repolarization Instability Manifested by Low-Frequency Oscillations of...

Area of Science:

• Cardiovascular Physiology
• Space Medicine
• Biomedical Engineering

Background:

• Space missions pose risks of ventricular arrhythmias and sudden cardiac death.
• Long-duration spaceflight and head-down bed rest (HDBR) alter cardiac function, affecting ventricular repolarization.
• Existing methods for assessing arrhythmic risk require novel approaches.

Purpose of the Study:

• To develop and validate new methods for quantifying Periodic Repolarization Dynamics (PRD).
• To assess the impact of long-term microgravity exposure on PRD.
• To evaluate the effectiveness of countermeasures against microgravity-induced cardiac changes.

Main Methods:

• Developed novel methods to quantify the Periodic Repolarization Dynamics (PRD) index.
• Recorded electrocardiograms (ECGs) from 42 volunteers before and after 60-day -6° HDBR.
• Evaluated PRD at rest and during orthostatic tilt table tests.

Main Results:

• Orthostatic tilt tests increase PRD, indicating sympathetic modulation of ventricular repolarization.
• Long-term microgravity exposure significantly increases PRD at rest and during tilt tests.
• Exercise-based countermeasures partially reversed microgravity-induced PRD changes, while nutrition-based ones did not.

Conclusions:

• Microgravity exposure elevates low-frequency oscillations in ventricular repolarization, increasing arrhythmia risk.
• These changes are amplified by sympathetic stimulation.
• Current countermeasures offer only partial protection against microgravity-induced cardiac effects.