Human hearts become more spherical in space, according to a new study of 12 astronauts.
Changes to the shape of the vital organ could lead to cardiac problems for space travelers exposed to long periods of microgravity.
Astronauts were trained to take ultrasound readings of their hearts. These measurements were taken before, during and after trips to space. Hearts were found to become more spherical by an average of 9.4 percent in the microgravity conditions present aboard the international Space Station.
"The heart doesn't work as hard in space, which can cause a loss of muscle mass. 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," James Thomas, lead scientist for ultrasound at NASA, and senior author of the study, said.
Arrhythmias sometimes occur during space flights. After returning to Earth, hearts return to their normal shape, but astronauts can still suffer from several effects of space travel. These include orthostatic hypotension, or a lightheaded feeling upon standing.
"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 in a press release.
As humans prepare to take the first steps toward colonizing the Moon and Mars, medical studies such of these are essential. A trip to the red planet would require space travelers to spend 18 months in weightlessness. Once on the surface of Mars, visitors or colonists will experience a planet with 37 percent of the gravity on Earth. The effects of this level of gravity after years, or decades, of exposure are not known. The first human mission to Mars may be a one-way trip. Currently, crews aboard the space station rotate shifts, each just six months long.
Investigations into the effects of space travel on human hearts can also help medical professionals design exercise routines for those undertaking journeys into the final frontier. This research could also benefit patients confined to bed for long periods of time, or those recovering from heart failure.
Hearts are not the only medical concern for mission managers. The long-term effect of radiation on space travelers is also a field of intense study.
Research into physiological changes in hearts during space travel was presented at the American College of Cardiology's 63rd Annual Scientific Session, on 29 March.
