Fitness Trackers May Help Detect Potentially Dangerous Irregular Heartbeats

BOSTON – Atrial fibrillation—an irregular and often rapid heart rate—is often asymptomatic, but it’s important to diagnose because it can lead to clots that travel to the brain to cause a stroke.

A recent clinical trial led by a team at Massachusetts General Hospital (MGH) indicates that Fitbit wearable devices can help spot undiagnosed atrial fibrillation and therefore identify patients who would benefit from stroke prevention therapies.

For the trial, which is published in Circulation, the researchers developed a novel algorithm that can detect irregular heart rhythms based on Fitbit sensors that measure pulse rate.

“Smartwatches and fitness trackers contain what are called photoplethysmography sensors to detect the pulse waveform, and software algorithms can be developed to infer the presence or absence of atrial fibrillation,” says lead author Steven A. Lubitz, MD, MPH, a cardiac electrophysiologist at MGH and an associate professor of medicine at Harvard Medical School.

“Since smartwatches and fitness trackers are common, they present a unique and growing opportunity to identify atrial fibrillation in large populations, with the potential to substantially improve health outcomes.”

Lubitz and his colleagues enrolled 455,699 US adults who did not have an atrial fibrillation diagnosis and were using compatible wearable Fitbit devices and Android or iOS smartphones.

Their novel algorithm identified irregular heart rhythms in 4,728 (1%) participants overall and among 2,070 (4%) participants aged ≥65 years. Among 1,057 participants with an irregular heart rhythm notification who then wore a one-week electrocardiogram patch monitor, atrial fibrillation was present in 340 (32.2%).

The primary outcome was assessed in 225 participants who had an irregular heart rhythm detection during continued electrocardiogram monitoring. Among these, atrial fibrillation was confirmed in 221, for what the team called a positive predictive value of 98%.

“These findings indicate that when a user sees a notification, there is a substantial likelihood that it represents atrial fibrillation,” says Lubitz. “Those receiving notifications may benefit from interaction with their physicians, who can determine what confirmatory diagnostic testing is appropriate and assess whether therapy to prevent strokes is indicated.”

Co-authors include Anthony Z. Faranesh, PhD, Caitlin Selvaggi, MS, Steven J. Atlas, MD, MPH, David D. McManus, MD, ScM, Daniel E. Singer, MD, Sherry Pagoto, PhD, Michael V. McConnell, MD, MSEE, Alexandros Pantelopoulos, PhD, and Andrea S. Foulkes, PhD.

This work was supported by Fitbit.

About the Massachusetts General Hospital

Massachusetts General Hospital, founded in 1811, is the original and largest teaching hospital of Harvard Medical School. The Mass General Research Institute conducts the largest hospital-based research program in the nation, with annual research operations of more than $1 billion and comprises more than 9,500 researchers working across more than 30 institutes, centers and departments. In August 2021, Mass General was named #5 in the U.S. News & World Report list of "America’s Best Hospitals." MGH is a founding member of the Mass General Brigham healthcare system.