The heart becomes more spherical when exposed to long periods of microgravity in space, according to a study of 12 astronauts. The research has implications if any progress toward a trip to Mars ever gets made. NASA already has a zero-risk culture and cute robots don't have heart attacks whereas a spaceflight of 18 months or more that could affect astronauts' heart strength may be a concern.
In space, no one can hear your heartbeats - as easily. The heart works a lot less and that leads to less muscle mass, even over a relatively short duration.
"The heart doesn't work as hard in space, which can cause a loss of muscle mass," said James Thomas, M.D., lead Scientist for Ultrasound at NASA, and senior author of the work presented at the American College of Cardiology's 63rd Annual Scientific Session. "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."
Exercise would obviously be one. Plenty of people are completely sedentary for 18 months and don't have heart attacks when they start moving around.
Thomas agrees, and says that exercise regimens developed for astronauts could also be used to help maintain heart health in people on Earth who have severe physical limitations, such as people on extended bed rest or those with heart failure regime. But that's not why the programs should be developed, any more than we built NASA to develop Tang. Instead, earth-bound doctors have likely already solved this problem and it just needs to be configured for the small confines of a spacecraft. Getting the heart pumping could be as simple as making the astronauts watch political commentary on MSNBC or Fox News.
The research team trained astronauts to take images of their hearts using ultrasound machines installed on the International Space Station. Twelve astronauts participated, providing data on heart shape before, during and after spaceflight.
The results show the heart in space becomes more spherical by a factor of 9.4 percent, a transformation similar to what scientists had predicted with sophisticated mathematical models developed for the project. By validating those models, the study could also lead to a better understanding of common cardiovascular conditions in patients on Earth.
"The models predicted the changes we observed in the astronauts almost exactly. 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," Thomas said.
The team is now working to generalize the models to analyze such conditions as ischemic heart disease, hypertrophic cardiomyopathy and valvular heart disease.
"The models could help us simulate those pathologies to understand the impact on cardiac function," Thomas said.
The astronauts' more spherical heart shape appears to be temporary, with the heart returning to its normal elongated shape shortly after the return to Earth. The more spherical shape experienced in space may mean the heart is performing less efficiently, although the long-term health effects of the shape change are not known.
Spaceflight is known to cause a variety of cardiac effects. Upon return to Earth, astronauts commonly become lightheaded or pass out in a condition known as orthostatic hypotension, in which the body experiences a sudden drop in blood pressure when standing up. Arrhythmias have also been observed during space travel, and there is concern that the radiation astronauts are exposed to in space may accelerate atherosclerosis. The research team is continuing to examine these and other potential cardiovascular effects.