Evaluation of the left ventricle contractility during and after 6 months on the ISS using a speckle tracking modality

Cardiac contractility can be evaluated during ultrasound evaluations using speckle tracking to map the motion of myocardium during the cardiac cycle. The purpose of the current study was to use this method to evaluate cardiac contractility in astronauts before, during, and after 6 months of spaceflight on the International Space Station.

Speckle tracking data were recorded from ten astronauts (1F) preflight (PRE), on flight day 150 (FD150) and approximately 4 days after returning to Earth (R4). A 2D apical view video of the left ventricle was captured at each time point for the evaluation of three measures of cardiac contractility: the mean displacement of speckles, the product of mean displacement and the number of speckles tracked, and the size of the area with speckles showing the greatest displacement.

A trend was found for mean speckle displacement to be affected by spaceflight and recovery (p = 0.052) with displacement potentially lower in seven of the ten astronauts on FD150. The product of speckle displacement and number of speckles was significantly lower inflight compared to R4 (p = 0.021). The area with the highest displacement was significantly reduced with spaceflight compared to PRE (p = 0.017). For all variables, values on R4 were not different from PRE.

Results indicate a mild reduction in cardiac contractility with spaceflight. All parameters returned quickly to preflight values by R4, suggesting that these changes are related to a reduction in physical activity and/or fluid blood volume rather than cellular remodeling of the myocardium.