A new study shows the Apple Watch's heart rate sensor, when paired with an artificial intelligence-based algorithm, can detect a serious and often symptomless heart arrhythmia, atrial fibrillation (AF). The new research uses a deep neural network based on photoplethysmographic (PPG) sensors commonly found in smart watches. The results of this study were presented today at Heart Rhythm 2017, the Heart Rhythm Society’s 38^th Annual Scientific Sessions in Chicago, Ill.
 
AF, the most common heart arrhythmia, affects more than 2.7 million American adults. While AF may present symptoms such as palpitations and fatigue, it is often asymptomatic, causing no alarm to doctors or patients and making diagnosis difficult. According to a national survey of 1,000 Americans, one in five Americans owns a wearable fitness tracker such as a smart watch or Fitbit.¹ With the growing number of people using this mobile technology, there is an opportunity to address public health issues such as undiagnosed AF in a way that is convenient for many.
 
The study enrolled 6,158 users of Cardiogram for Apple Watch into the UCSF Health eHeart Study. Data from those participants—including 139 million heart rate measurements and 6,338 mobile ECGs—was used to train a deep neural network to automatically distinguish atrial fibrillation from normal heart rhythm.
 
The deep neural network was validated against a cohort of 51 patients set to undergo cardioversion, a procedure that restores the heart to a normal rhythm. Each patient wore an Apple Watch for 20 minutes pre- and post cardioversion. With a 12-lead electrocardiogram as a reference standard, the DNN correctly detected atrial fibrillation with an accuracy (c-statistic) of 97 percent, a sensitivity of 98.04 percent, and a specificity of 90.20 percent, higher than previously-validated algorithms for detection of AF.
 
“Our results show that common wearable trackers like smartwatches present a novel opportunity to monitor, capture and prompt medical therapy for atrial fibrillation without any active effort from patients,” said senior author, Gregory M. Marcus, M.D., MAS endowed professor of atrial fibrillation research and director of clinical research for the Division of Cardiology at the University of California, San Francisco. “While mobile technology screening won’t replace more conventional monitoring methods, it has the potential to successfully screen those at an increased risk and
lower the number of undiagnosed cases of AF.”
 
The Health eHeart Study seeks to gather more data about heart health from more people than any research study has done before and develop strategies to prevent and treat all aspects of heart disease. Cardiogram seeks to predict and prevent heart disease using artificial intelligence. The authors of the Apple Watch study are currently working on expanding the number of participants, exploring success rates of self-diagnosis, and testing the ability of the deep neural network to identify other health conditions.
 
Heart Rhythm 2017 is the most comprehensive educational program for heart rhythm professionals, featuring more than 250 educational sessions and more than 130 exhibitors showcasing innovative products and services. The Heart Rhythm Society’s Annual Scientific Sessions have become the must-attend event of the year, allowing the exchange of new vital ideas and information among colleagues from every corner of the globe.
 
The Heart Rhythm Society is the international leader in science, education and advocacy for cardiac arrhythmia professionals and patients, and the primary information resource on heart rhythm disorders. Its mission is to improve the care of patients by promoting research, education and optimal health care policies and standards. Incorporated in 1979 and based in Washington, DC, it has a membership of more than 5,900 heart rhythm professionals in more than 70 countries around the world.

Reference:
1. PwC Health Research Institute and Consumer Intelligence Series. (2014) “Health wearables: Early days”.