Apple Watch can detect irregular heart rate, but more research needed—Stanford study

Results of a Stanford Medicine study found that the Apple Watch can potentially spot a heart problem that might lead to stroke. (Apple)

For 8 of 10 Apple Watch wearers, the device could potentially spot a heart problem that might lead to stroke, according to a new study out of Stanford Medicine.

The Stanford Medicine Apple Heart Study, based on 400,000 participants, found that the Apple Watch detected irregular heart rhythms in about 2,000 participants and 84% of wearers who received irregular heartbeat notifications were in atrial fibrillation.

Stanford Medicine researchers presented the findings from the large-scale, Apple-funded study at the American College of Cardiology’s 68th Annual Scientific Session and Expo in New Orleans over the weekend and touted the results as showing the potential role for consumer wearable devices to provide an early warning for life-threatening health conditions.

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As atrial fibrillation is a leading cause of stroke and hospitalization in the United States, researchers hope that devices like the Apple Watch can help with early detection of the condition. Patients with untreated atrial fibrillation are five times more likely to have a stroke, according to the American Heart Association.

RELATED: Stanford kicks off Apple Heart Study to screen and virtually triage patients with irregular heartbeats

For Apple, the study results help to strengthen its position as the consumer tech company moves further into healthcare.

The study did not include the most recent Apple Watch, which features a built-in electrocardiogram, as it was released after the study’s launch.

“The results of the Apple Heart Study highlight the potential role that innovative digital technology can play in creating more predictive and preventive health care,” Lloyd Minor, M.D., dean of the Stanford School of Medicine, said. “Atrial fibrillation is just the beginning, as this study opens the door to further research into wearable technologies and how they might be used to prevent disease before it strikes—a key goal of precision health.”

A smaller study published last year found the Apple Watch, paired with an algorithm, was only 68% accurate at detecting atrial fibrillation among 1,600 patients. At the time, Stanford University cardiology researcher Mintu Turakhia, M.D., called the results “humbling" and urged the industry to “think creatively but prudently” about how new technology is used to predict disease.

Turakhia, an associate professor of cardiovascular medicine, was a principal investigator on the Apple Heart Study as well.

Stanford collaborated with Apple and telemedicine company American Well for the virtual app-based study and enrolled over 400,000 participants from all 50 states in a span of only eight months.

Apple and Stanford created the study to evaluate Apple Watch’s irregular rhythm notification, which occasionally checks the heart's rhythm in the background and sends a notification if an irregular heart rhythm appears to be suggestive of atrial fibrillation. As part of the study, if an irregular heart rhythm was identified, participants received a notification on their Apple Watch and iPhone and were asked to schedule a telehealth consultation with a doctor involved in the study through American Well. Study participants were then sent ambulatory ECG patches for additional monitoring.

According to the study findings, only 0.5% of the 400,000 participants received irregular pulse notifications from the Apple Watch. Researchers noted that this an important finding “given concerns about potential over-notification.”

In a press release, Apple said this finding illustrates the feature’s ability to give a user important health information “without creating an unnecessary burden to their doctor’s schedule.”

“Many participants sought medical advice following their irregular rhythm notification, using the information to have more meaningful conversations with their doctors,” Apple said.

Key findings of the study include:

  • 84% of the time, Apple Watch wearers who received irregular pulse notifications from the device were found to be in atrial fibrillation at the time of the notification, according to the study.
  • Comparisons between irregular pulse-detection on Apple Watch and simultaneous electrocardiography patch recordings showed the pulse detection algorithm (indicating a positive tachogram reading) has a 71% positive predictive value.
  • 34% of the study participants who received irregular pulse notifications and followed up by using an ECG patch over a week later were found to have atrial fibrillation. Since atrial fibrillation is an intermittent condition, researchers said it is not surprising for it to go undetected in subsequent ECG patch monitoring.
  • 57% of those who received irregular pulse notifications sought medical attention, according to the study.

Marco Perez, M.D., a principal investigator on the study and associate professor of cardiovascular medicine, said the performance and accuracy of the device provide important information as researchers try to understand the potential impact of wearable technology on the health system.

“Further research will help people make more informed health decisions,” Perez said.

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