A change of heart…in space

Astronauts’ hearts become more spherical in space say NASA scientists, which could lead to cardiac problems in space, and have important implications for manned missions to Mars. A study of 12 astronauts who were trained to take images of their hearts using ultrasound machines installed on the International Space Station found that when exposed to long periods of microgravity, the heart changes shape, becoming more spherical. During this time, the heart performs less efficiently. “The heart doesn’t work as hard in space, which can cause loss of muscle mass,” said James Thomas, the Moore Chair of Cardiovascular Imaging and lead scientist for Ultrasound at NASA. “That can have serious consequences after the return to Earth, so we’re looking into whether there are measures that can be taken to prevent or counteract that loss.” Knowing the amount and type of exercise astronauts need to do to keep their heart healthy is important to guarantee their safety on long flights like a mission to the Red Planet, but these regimes may also be used to maintain heart health in patients on Earth with severe physical limitations such as those on extended bed rest or with heart failure regime. The research – reported at the American College of Cardiology’s 63^rd Annual Scientific Session – shows that the heart becomes more spherical by a factor of 9.4%. This was a similar figure to that predicted by scientists using sophisticated mathematical models developed for the project. By validating these models, the study could also lead to a better understanding of common cardiovascular conditions in patients of Earth. “The model predicted the changes we observed in the astronauts almost exactly,” said Thomas. “It gives us confidence that we can move ahead and start using these modes for more clinically important applications on Earth, such as to predict what happens to the heart under different stresses.” The team is now working to generalise the models at analyse ischemic heart disease, hypertrophic cardiomyopathy and valvular heart disease, amongst other cardiological conditions. But astronauts need not worry – the heart returns to its normal shape shortly after return to Earth, however the long-term effects of the shape change are not known.