Using the devices, the emergency physicians identified the time his heart arrhythmia started, which allowed them to treat his new-onset atrial fibrillation and discharge him home.
"Using the patient's activity tracker - in this case, a Fitbit - we were able to pinpoint exactly when the patient's normal heart rate of 70 jumped up to 190," said Alfred Sacchetti, from Our Lady of Lourdes Medical Centre in US.
"That was well within the 48-hour window needed to consider him for rhythm conversion, so we cardioverted him and sent him home," he said.
The patient with a history of seizures but no history of cardiac disease or prior episodes of atrial fibrillation came to the emergency department following a seizure.
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He had an irregular heart rate ranging between 130 and 190 beats per minute. He was medicated with oxcarbazepine and diltiazem, the doctors said.
His heart rate returned to normal (between 80 and 100 beats per minute) but the atrial fibrillation remained.
Because the patient had not experienced any symptoms during his current episode of atrial fibrillation, it was not possible to assign an onset time for his arrhythmia.
The staff accessed the smartphone application connected with his activity tracker and discovered the onset time for his atrial fibrillation was 3 hours prior to coming to the emergency department.
After cardioverting the sedated patient, emergency department staff checked the smartphone app again, which accurately recorded the change in heart rate consistent with a rhythm change from atrial fibrillation to normal rhythm.
"Not all activity trackers measure heart rates, but this is the function of most value to medical providers," said Sacchetti.
"Dizziness with a heart rate of 180 would be approached very differently from the same complaint with a heart rate of 30," he said.
"At present, activity trackers are not considered approved medical devices and use of their information to make medical decisions is at the clinician's own discretion," he said.
"However, the increased use of these devices has the potential to provide emergency physicians with objective clinical information prior to the patient's arrival at the emergency department," Sacchetti added.