Apple Heart Study Shows Wearable Technology Can Help Detect Atrial Fibrillation

Apple heart study Afib
Image: Apple

A study from the Stanford University School of Medicine and Apple has shown that wearable technology can safely detect irregular heartbeats, known as Atrial Fibrillation (AFib). The study was published in the New England Journal of Medicine.

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“The study’s findings will help patients and clinicians understand how devices like the Apple Watch can play a role in identifying atrial fibrillation, a deadly and often undiagnosed disease,” said Mintu Turakhia, MD, associate professor of cardiovascular medicine. “Additionally, these important findings lay the foundation for further research into the use of emerging wearable technologies in clinical practice and demonstrate the unique potential of large-scale app-based studies.”

Atrial fibrillation is a type of irregular heartbeat (arrhythmia) that happens when electrical impulses fire off from different places in the atria (the top chambers of the heart) in a disorganized way. The condition increases your risk of strokes, heart failure and other heart-related complications. It is a leading cause of stroke and hospitalization in the United States, but due to its elusive and sporadic symptoms, the condition often goes undetected.

To participate in the study, each individual needed an Apple Watch (series 1, 2 or 3) and an iPhone. The Series 4 and 5 Apple Watches, which feature a built-in ECG, weren’t part of the study, as they were released after the study’s launch.

During the study, the researchers found that only 0.52% of participants received an irregular pulse notification, assuaging concerns about potential over-notification in healthy participants. Those who were flagged for an irregular pulse received follow-up care through a heart-monitoring technique called an electrocardiography (ECG) patch, which continuously monitors electrical impulses generated by the heart, for one week.

Image showing Atrial Fibrillation
Image: Atrial Fibrillation by BruceBlaus (Wikimedia commons)

Of those who received a notification and were monitored by the ECG patch about two weeks later, 34% were found to have AFib. Because atrial fibrillation is an intermittent condition, it’s not surprising for it to go undetected in subsequent ECG patch monitoring. Comparison between irregular pulse-detection on Apple Watch and simultaneous electrocardiography (ECG) patch recordings showed the pulse detection algorithm has an 84% positive predictive value.

During ECG patch monitoring, participants’ Apple Watches continued to monitor pulse irregularities. If a participant had an irregular pulse detected, 84% of the time this was confirmed to be AFib on the simultaneous ECG patch. This, said Perez, demonstrates that the algorithm in the Apple Watch can successfully identify atrial fibrillation. Information from this study could be used to inform further clinical evaluation.

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The study also showed how digital health alerts can enhance engagement with the health care system overall. A survey of participants who received an irregular pulse notification showed that 76% contacted either the telehealth provider or a non-study provider, suggesting that many actively sought medical attention as a result of an irregularity identified by their Apple Watch, said Turakhia.

With more than 400,000 participants enrolled in eight months, the Apple Heart Study is the largest virtual study to date.

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Cathy Russey () is Online Editor at WT | Wearable Technologies and specialized in writing about the latest medical wearables and enabling technologies on the market. Cathy can be contacted at info(at)