A study of 12 astronauts show how hearts can temporarily change their shape during long periods of microgravity -- a change that may lead to cardiac problems later on.
“The heart doesn’t work as hard in space, which can cause a loss of muscle mass,” James Thomas of NASA says in a news release. “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.”
There are plenty of health issues to worry about in zero gravity: for starters, bone loss, anemia, blurry vision, and loss of slow-twitch muscles. (Although, we did learn some good news earlier this year: evidence of thyroid cancer cells becoming less aggressive in space.) Knowing the amount and type of exercise astronauts need to keep the heart healthy will be crucial to guarantee their safety on long missions, such as the 18 months of spaceflight required for Mars.
Thomas and colleagues trained astronauts to take images of their hearts using ultrasound machines installed on the International Space Station. A dozen of them provided data on their heart shape before, during, and after spaceflight. These showed how their hearts became more spherical by a factor of 9.4 percent, which validate predictions from mathematical models.
The rounder shape appears to be temporary, fortunately, with the hearts returning to their normal, elongated shape shortly after the astronauts returned to Earth. But the transformation experienced in space suggests that the heart isn’t performing as efficiently -- although doctors don’t really know about the actual long-term health effects of this kind of change.
Now that the models are validated, the researchers hope to use them to understand cardiovascular conditions on Earth. “The models predicted the changes we observed in the astronauts almost exactly,” Thomas says. “It gives us confidence that we can move ahead and start using these models for more clinically important applications on Earth, such as to predict what happens to the heart under different stresses." The team is working on generalizing the models to analyze conditions like ischemic heart disease, hypertrophic cardiomyopathy, and valvular heart disease.
Thomas adds that exercise regimens developed for astronauts in microgravity could also be used to help earthlings with severe physical limitations, such as people on extended bed rest or patients with heart failure.
The findings were presented at the American College of Cardiology’s 63rd Annual Scientific Session.
Image: NASA Spinoff