Deanna Recktenwald received an unusual notification from her Apple Watch Series 2 in April 2018.

"Seek medical attention," the display read after the 18-year-old's resting heart rate skyrocketed to 190 beats per minute. A normal resting heart rate for adults 18 and older is between 60 and 100 beats per minute, according to the Mayo Clinic.

The Tampa Bay area teenager, who said she didn't feel any alarming symptoms, was immediately taken to an urgent care facility by her mother, Stacey Recktenwald. Doctors told the family that the high school senior was in kidney failure.

"Without this watch, I fear she would've been one of the kids on the news – the healthy kid that goes off to college and dies in their sleep," Stacey told USA TODAY.

There is a growing list of testimonies that demonstrate how smartwatches are going beyond fashionable lifestyle conveniences or workout tools, doubling as SOS signals during sudden medical emergencies.

Utah native Michael Glenn, 34, said that he bought a used Fitbit so that he could occasionally count calories and monitor his eating habits. In 2018, the device alerted him that his heart rate was a sluggish 40 beats per minute, well below what is considered normal.

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"My wife had to convince me to go to the hospital," Glenn said. After immediately being airlifted for emergency surgery, Glenn found out his right coronary artery was 100 percent blocked and his central artery was 80 percent blocked.

"Doctors said I had a 50/50 chance of survival," Glenn said. "I’m just a husky guy who bought a Fitbit so I could continue to eat more pizza. Turns out, it saved my life."

An Apple Watch saved Christina's Ling life in December, according to the Edgewater, New Jersey resident.

"The watch told me that my heart rate was 150 even though I was sitting idle for 10 minutes," said Ling, 45. After going to the hospital, she found out she had a cardiac tamponade, abnormal fluid around the heart.

"My heart was basically suffocating," Ling said. "But what's really crazy is, I thought it was just the flu and I never set up my Apple Watch to send me any health alerts. It totally saved my life."

And in the case of the Florida teenager battling kidney disease, the Apple Watch's emergency notification propelled the entire family to get checked for kidney disease. Deanna's mother, three sisters and father all tested positive.

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The wellness devices' ability to identify medical emergencies and underlying health conditions aren't just by happenstance. These gadgets were designed that way.

Since 2014, Fitbits, which aren't FDA-approved medical devices, have used tracking technology to monitor heart beats automatically, all-day, during workouts and beyond. This perpetual tracking can give wearers of the device the ability to document heart rhythms that may not be picked up during a planned trip to the doctor's office.

"We are focused on developing hardware, software and services that can give users an even more complete picture of their health,” the makers of the popular workout gadget said in a statement. "Fitbit technology has redefined how users can learn about their health by making data that was previously only available in a lab accessible on the wrist."

There are several features for Apple Watch that are able to help people in dire circumstances including the ability to call 911 right from the wrist, fall detection, irregular heart rhythm notifications and an ECG app.

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Apple CEO Tim Cook recently told USA TODAY: "I think you'll be able to look back at some point in the future and Apple's greatest contribution will have been to people's health."

Some experts say that wearables may be on track to offer clinical-grade patient data that doctors can use to make diagnoses.

"I look back to the turn of the millennium and we were starting to talk about remote monitoring from doctor's offices. That involved large devices, the size of TV sets being transported inconveniently into the patient's home," said Kevin McGinnis, communications and technology adviser for the National Association of EMS officials.

"Today, we have Apple watches with electrocardiogram features. You can remotely create a PDF of your heart rhythm and send it directly to your doctor," McGinnis said. He said that in the future, wearables will be able to "pump insulin, defibrillate the heart, or pump some other drug as a result of an emergency happening in the body."



For now, the type of information gathered from smartwatches can give doctors insight into daily patient behavior that can be used to improve care.

James E. Ip, associate professor of clinical medicine at the research center Weill Cornell Medicine, published a report in January 2019 that spotlighted the ways fitness watches can be used to identify heart arrhythmia and other a-typical heartbeat patterns.

Ip said that he bought his father a Fitbit Charge 2 HR in 2016. The device picked up his dad's abnormal heartbeat almost immediately. Upon further testing, Ip's father was diagnosed with supraventricular tachycardia, sudden bursts of an abnormally fast heartbeat that can occur at rest.

A graph on the Fitbit app showed that the 71-year-old's heartbeat sporadically entered the cardio workout range, "even though he was completely sedentary," Ip said. His father was subsequently treated with catheter ablation, a minimally invasive procedure where a thin, flexible tube is implanted into blood vessels around the heart.

Some health insurance agencies have begun partnering and collaborating with smartwatch makers to deliver wearable devices directly to consumers.

In early 2019, Fitbit quietly introduced a new activity and sleep tracker that can only be obtained through health plans or employers. Called the Fitbit Inspire, the devices were designed to make "developing healthy habits easier for everyone," according to the company's website.

The CVS Health-owned insurer Aetna partnered with Apple to launch its wellness app Attain in January 2019. The app tracks exercise and sleep behavior and offers rewards to users for healthy habits. One of the rewards is a free Apple Watch.

"We’re designing Attain to be personalized and clinically relevant to where each individual is in their health journey," said Alan Lotvin, M.D., executive vice president of transformation for CVS Health.

In a 2016 Aetna and Apple collaboration, 90 percent of participants reported a health benefit from their use of Apple Watch, Aetna reported.

Ip said smartwatches that lead to the diagnosis and treatment of medical conditions "are likely to become more common as the use of consumer health-based technology expands."

In fact, worldwide sales of wearables will grow by an average of 20 percent each year over the next five years, becoming a $29 billion market with 243 million unit sales by 2022, according to industry analyst CCS Insight.

In 2018, U.S. smartwatch sales totaled nearly $5 billion, more than double what they were in 2017, according to market research firm NPD Group.

Apple was the clear market leader, followed by Samsung and Fitbit. Thanks largely to its popular Gear line and Galaxy Watch, Samsung won about 6 percent of the global wearables market toward the end of 2018, according to market intelligence firm IDC. Fitbit held 10.9 percent, while Apple captured 13.1 percent following the launch of it's Series 4 Watch that's approved for medical use.

Xiaomi, a Chinese electronics company, took the top position grabbing 21.5 percent of worldwide sales.

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Still, medical experts say relying solely on smartwatches for medical advice isn't a good idea. Potential side effects include accidental 911 calls and unreliable readings.

In January 2019, the Apple Watch Series 4 caused frustration among emergency dispatch centers in ski resort towns across Colorado, such as Vail.

When some skiers hit the slopes they forgot to turn off a fall detection service. After they slipped, injured or not, a 911 call was triggered by the watch.

"We’ve seen that in the past with (other medical alert systems), the ones that elderly and housebound people tend to have," said McGinnis who is the communications technology adviser for several national EMS associations. "We want to avoid a lot of unfounded alert systems."

In addition to occasional false alarms, "certain heart rhythms can throw a sensor off, leading to a perceived high heart rate reading," said Ip, a cardiac electrophysiologist. "If a device is too loose on your wrist a reading can be off. Skin color, ambient environments and other factors can also produce false readings."

Ip said that in some cases information obtained by fitness trackers can be challenging to interpret and analyze by doctors.

"These devices on aren’t perfect by any means," Ip said. "But when taken together with medical-grade devices, these things can be potentially helpful. Sometimes, it’s better than having nothing at all."

Follow Dalvin Brown on Twitter: @Dalvin_Brown