Heather Hendershot had no idea something might be wrong last month as she relaxed in her Scranton home.
With her two kids asleep, she sat down to watch television with her husband, Corey. But around 9 p.m. that Saturday, her new Apple Watch began to beep.
Her heart rate was around 120 beats per minute — above normal for a 25-year-old resting on the couch. Every 10 minutes, she said, the watch warned her of a rapid heartbeat. It was the only warning sign of a potentially serious condition.
Hendershot first thought the watch was wrong, since she didn’t feel abnormal. But when she timed her heart beat herself, she found it was accurate. According to the watch, it reached above 160 beats per minute that night and by the next afternoon the couple decided to visit an urgent care clinic.
“I thought I might be sick and my body was just fighting infection, but my husband is a worry wart,” she said.
Physicians at the clinic confirmed the high heartbeat, but couldn’t determine the problem, so the couple went to Stormont Vail Health’s emergency room where nurses quickly dubbed her “The Apple Watch Patient.”
Blood tests there determined Hendershot had moderate to severe hyperthyroidism, said Alan Wynne, an endocrinologist at the Cotton O’Neil Diabetes and Endocrinology center at Stormont Vail, who treated Hendershot.
Hyperthyroidism happens when the thyroid pumps too much hormone into the bloodstream, and it’s usually accompanied by a rapid heart rate, along with tremors, shortness of breath and chest pain. Untreated, it can lead to a “thyroid storm,” an extreme situation that can be fatal in some patients, Wynne said.
Hendershot had none of the classic symptoms, besides the beeping Apple Watch. Wynne said he was “startled and surprised” to hear the watch was her only symptom.
“My reaction was to smile at her and pause. I asked her twice at first and a third time later, ‘Wait a minute, you didn’t feel anything?’” he said. “I’ve been doing this 25 years and it’s the first time ever I’ve heard someone tell me they didn’t notice anything and were later diagnosed with severe hyperthyroidism.”
It was also the first time a smartwatch detected symptoms in Wynne’s career.
Apple Watches rely on photoplethysmography — a long, complicated sounding word with a fairly simple premise. Because blood with oxygen is red, it absorbs green light. The watch uses green LED lights paired with light‑sensitive photodiodes to detect the amount of blood flowing through a person’s wrist, according to Apple’s website. During beats the amount of blood in the wrist is greater, and between beats it’s less. Flashing the LED lights hundreds of times per second calculates the number of times the heart beats. The sensor can support beats ranging from 30 to 210 per minute.
Wynne said devices like smartwatches might increase the chances of catching health problems early.
“To have something like that monitoring you or me in the background, it’s really brought us to a new threshold,” he said.
“If I hadn’t been wearing it, I wouldn’t have known anything was wrong,” she said.