Key result
Long-term (60 days) exposure to simulated microgravity via head-down bed-rest increased T-wave alternans indices upon return to normal gravity, indicating incipient electrical instability.
Why the study?
The study was conducted to assess the effects of different durations of simulated microgravity on ventricular repolarization in terms of T-wave alternans and determine whether ventricular repolarization heterogeneity increases once normal gravity is restored.
Does simulated microgravity exposure via head-down bed-rest increase T-wave alternans in healthy volunteers?
Observational (n=63)
Does simulated microgravity exposure via head-down bed-rest increase T-wave alternans in healthy volunteers?
Long-term simulated microgravity (60 days) followed by restoration of normal gravity increases ventricular repolarization instability, highlighting potential arrhythmic risks for astronauts returning from long spaceflights.
Answers are grounded in this paper and cite their sources.
May warrant arrhythmia monitoring after prolonged bed rest; leaves open validation in actual spaceflight.
OBJECTIVE: To assess the effects of different durations of simulated microgravity exposure on ventricular repolarization (VR) in terms of T-wave alternans (TWA) as well as to test whether an increase in VR heterogeneity could be detected once normal gravity was restored. APPROACH: A total of 63 healthy volunteers were recruited in several head-down bed-rest (HDBR) experiments in the context of the European Space Agency bed-rest strategy. TWA is evaluated during the night period using ambulatory ECG recordings, before, during and after long- (60 d), mid- (21 d) and short- (5 d) duration HDBR by the long-term averaging technique. MAIN RESULTS: 5-21 d of exposure to simulated microgravity by means of the HDBR model do not lead to a significant increase of cardiac electrical instability in healthy myocardial substrates up to the point of eliciting TWA on the surface ECG. However, TWA indices increased after long-term HDBR exposure, once normal gravity was re-established, indicative of incipient electrical instability on VR at the conclusion of 60 d of HDBR. SIGNIFICANCE: The results of this work underline the importance of focusing future research on immediate effects after long-term microgravity exposure, both simulated by HDBR or from space mission scenarios, once partial gravity conditions are re-established. A deeper insight in the understanding of human body reactions in these scenarios results crucial in the design of future long-duration spaceflight missions, to mitigate any potential risk that can limit astronaut's performance.
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Martín-Yebra et al. (2019) conducted an observational in Healthy volunteers (n=63). Simulated microgravity exposure via head-down bed-rest (HDBR) vs. Baseline (before HDBR) was evaluated on Ventricular repolarization in terms of T-wave alternans (TWA). Long-term (60 days) exposure to simulated microgravity via head-down bed-rest increased T-wave alternans indices upon return to normal gravity, indicating incipient electrical instability.
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