Researchers in the midst of a several years' study of how astronauts' hearts react during long space voyages reported initial findings that they say could help improve cardiac care on Earth.
They found that astronauts benefitted from certain types of exercise, something that could help patients with heart failure or abnormal heartbeats, or those who are bedridden after surgery, a stroke, or during pregnancy, whose hearts atrophy much like an astronaut's in space.
Heart muscles don't have to work as hard to circulate blood in space because gravity doesn't exert the same force. Astronauts returning from missions frequently feel lightheaded and sometimes pass out. After weeks or months in space, the heart appears to shrink, cardiologists say, blood volumes decrease, and the astronaut can experience hypotension, or abnormally low blood pressure.
A study is looking at astronauts' hearts. NASA
WHAT'S LOST IN SPACE
Studying how astronauts' bodies change in space may help patients on Earth.
- Heart mass decreases up to 25%
- Blood volume decreases up to 20%
- Bone density decreases about 3%
- Blood pressure stays relatively the same. (Back on Earth, blood pressure can decrease by 20% to 25% or even more.)
Source: Benjamin Levine; Michael Bungo
The research is in its early stages, but some of it offers fresh interventions for heart patients. Benjamin Levine, one of the leaders of the NASA project, is studying astronauts exercising in space to help patients with what he calls "Grinch Syndrome," characterized by low blood pressure and the inability to stand up without losing consciousness. (The name refers to how it causes the heart to be two sizes too small like that of the Dr. Seuss character.) Dr. Levine found that seated exercise, such as using a rowing machine, can aid those patients.
The cardiologists presented the research from the NASA-funded project last week at a symposium held every other year called "Humans in Space," and earlier this month at the annual meeting of the American College of Cardiology.
"Cardiovascular research in space gives us the unique opportunity to study the effect of gravity on the heart and has led to novel understandings and therapies," said Dr. Levine, a cardiologist at University of Texas Southwestern Medical Center.
Twelve astronauts are expected to undergo detailed ultrasounds while in space and MRIs before and after flight for half a year. The project has been collecting data for two years and so far five astronauts have completed the testing. In addition to changes in blood volumes and heart size, researchers are also investigating reports of heart palpitations, known as arrhythmias, in space.
About 25% to 30% of astronauts may have trouble maintaining their blood pressure when they return from trips lasting less than 30 days, while 80% have low blood pressure and experience symptoms like tunnel vision and cold sweats after six-month missions, said Steven H. Platts, head of the cardiovascular laboratory at NASA's Johnson Space Center.
One of the goals of the NASA study is to help astronauts to someday travel longer and farther, perhaps even on a more than two-year mission to Mars. "The big question for even longer missions is, do the heart problems plateau or get worse?" Dr. Platts said.
Major construction of the International Space Station was completed last year, giving the scientists a new lab. "Medical research didn't have a very permanent role [in the space program] until recently," said Michael Bungo, professor of cardiology at the University of Texas Medical School who is co-investigator on the NASA project along with Dr. Levine.
Data from the first four astronauts confirms that they do in fact lose heart mass in space, but that exercise may counteract the problem. The amount of blood the heart pumps in space determines how much heart mass the astronauts lost, according to research presented last week.
Jeff Williams, an astronaut who participated in the study while on the International Space Station, said: "On all my flights, short and long, my perceived level of fitness was impacted and we don't really understand why."
On the space station, astronauts are supposed to work out for about two hours each day, mostly on a treadmill or bicycle onto which they are strapped.
Dr. Levine is studying how rowing on a stationary machine called an ergometer could cut down on the time astronauts have to spend working out to get the same effect. Dr. Levine presented research last week indicating that as little as 30 minutes a day of rowing could be as effective as 90 minutes of cycling.
He applied the research to patients with Grinch Syndrome or Postural Orthostatic Tachycardia Syndrome, which results mostly after prolonged bed rest.
One of Dr. Levine's Grinch Syndrome patients, Elisabeth Rybak, 47 years old, of New Brunswick, Canada, said at first she had to "crawl onto the rowing machine," and "you're ruined" after the tough workouts. She now credits them, plus a salt-heavy diet Dr. Levine prescribed, with a near complete recovery.
Another result of the NASA study was detailed models of how the heart reacts in space. The models could be used by cardiologists on Earth to predict how a heart might respond to other stresses and could help patients with heart failure and coronary artery disease, said James Thomas, a cardiologist at the Cleveland Clinic who presented the study at this month's American Heart Association meeting.
His team also showed that older ultrasound machines, such as the 10-year-old machine used on the International Space Station, can be used to measure strain within the heart.
Previously, cardiologists thought that new machines were needed to track strain—the change in the length of a muscle and an early indicator of problems. This could accelerate how often cardiologists track strain and lead to improvements, for instance, in monitoring heart function of chemotherapty patients, Dr. Thomas said.
Additionally, astronauts on the space station are being trained in how to give ultrasounds to their peers while being guided by an expert on Earth, said NASA's Dr. Platts. Remote use of ultrasound machines could accelerate their use and improve diagnoses if replicated in rural areas or hard-to-reach areas, he said.
Write to Avery Johnson at avery.johnson@WSJ.com
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