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How a Fitness Tracker Spotted a Woman's Life-Threatening Condition
The Fitbit Charge 2.
Credit: Jeremy Lips, for Live Science

A Connecticut woman is crediting her Fitbit with saving her life, after the device detected signs of life-threatening blood clots.

The woman, 73-year-old Patricia Lauder, had recently retired and bought a Fitbit to help her get in shape, according to a statement from the University of Connecticut, where Lauder was treated. But then, she began to feel ill, even though doctors' tests for health problems came back negative.

She also noticed that her heart-rate reading on her Fitbit was gradually increasing, until one day, it spiked to 140 beats per minute. She called 911 and was taken to the hospital, where tests showed that she had a condition called pulmonary embolisms, or blood clots in her lungs. Doctors gave her anti-clotting medication, which got rid of the clots.

"If I didn't have a Fitbit on my wrist, I would never have known that my heart rate was getting dangerously high," Lauder told UConn Today, the news website for the university. "And I might not be here to tell my story." [Top 10 Amazing Facts About Your Heart]

Experts say that, because some fitness trackers include heart rate monitors, the devices can potentially alert people to certain health problems that cause changes in heart rate.

"Heart rate is a general signal for how much stress your body's under," Dr. Allen Taylor, a cardiologist and professor of medicine at Georgetown University School of Medicine in Washington, D.C., told Live Science in a 2015 interview. Like a fever, a high heart rate could be a symptom of many conditions, so it cannot be used by itself to make a diagnosis, Taylor said. But "for certain conditions, [if] patients find their heart rates running faster, it could alert them to say 'something's not right here,' Taylor said.

A rapid or irregular heartbeat can be a sign of a pulmonary embolism, according to the Mayo Clinic. The blockage caused by the clots can require the heart to start working harder to pump blood through vessels, and this can also lead to an increase in blood pressure inside the lungs, the Mayo Clinic says.

Other conditions that a fitness tracker might detect include atrial fibrillation (an erratic heartbeat), anemia (a low red blood cell count) and an overactive thyroid. All of these conditions can lead to a faster-than-normal heart rate. A normal resting heart rate is between 60 and 100 beats per minute, according to the Mayo Clinic.

In September 2015, a high school senior credited his Apple Watch with saving his life, when the device showed he had a heart rate of 145 beats per minute. An exam revealed that he had rhabdomyolysis, a condition in which muscles release a protein that damages the kidneys and other organs.

And last year, doctors in New Jersey used data from a man's Fitbit to determine how to treat him when he arrived at the ER with a rapid and irregular heart rate.

Still, it's important to note that having a normal heart rate doesn't necessarily mean you're healthy, Taylor said.

And fitness trackers like the Fitbit aren't approved medical devices, so they cannot be used to diagnose cardiovascular conditions. A study published last year found that wrist-worn heart rate monitors, which are typically used on fitness trackers, are not as accurate as chest strap monitors. The researchers advised fitness-tracker users to be aware that the devices' heart-rate readings aren't always accurate.

Original article on Live Science.