An 18-year-old girl named Sarah-Jayne McIntosh has her Fitbit to thank after it alerted her about a drastic increase in her heart rate while she was studying. According to Southport Visiter, the teen was preparing for an upcoming exam when her heart rate jumped from 84 beats per minute to 210 bpm. McIntosh immediately sprung into action and phoned an ambulance for herself. 

Southport Visiter explains in its Jan. 2016 story that McIntosh was taken to a local hospital where doctors ran tests, which revealed that the teen had a heart issue. McIntosh described to the news source what doctors told her was happening in her heart.

"Apparently one pathway from one chamber to the heart from the other was misfiring and instead of the chambers beating one after another like it normally should, they were beating at the exact same time, which was causing my heart rate to increase. The doctor said I had two heartbeats. I had a resting rate of 190 (bpm) and they couldn't get it to lower." 

McIntosh also explained that after failed attempts of using shock therapy to lower the heart rate, medical staff administered a medication which slowed her heart down, Southport Visiter explains. 

Doctors told the teen that if it wasn't for the Fitbit and her calling an ambulance, she could have gone into cardiac arrest and possibly died.