A paper describes the design of this unique clinical trial, the largest screening study on atrial fibrillation ever done. Enrollment, which was conducted through an iPhone app, is now closed. The study has entered the final phase of data collection and will be completed early next year, the researchers said. The Stanford team is led by principal investigators Mintu Turakhia, MD, associate professor of cardiovascular medicine, and Marco Perez, MD, assistant professor of cardiovascular medicine, and by study chair Kenneth Mahaffey, MD, professor of cardiovascular medicine. “We hope this study will help us better understand how wearable technologies can inform precision health,” said Lloyd Minor, MD, dean of the School of Medicine. “These new tools, which have the potential to predict, prevent and manage disease, are finally within our reach.”
The Food and Drug Administration announced in September that it had cleared two mobile medical apps designed by Apple to work on the Apple Watch. One app uses data from new hardware on the Apple Watch Series 4 to take an electrocardiogram by touching the button on the side of the device. The other app uses data from an optical sensor available on the Apple Watch Series 1 and later to analyze pulse data to identify irregular heart rhythms suggestive of atrial fibrillation and notify the user. The Apple Heart Study involves only this second app. “The advantage of the app that uses the optical sensor is that it can check for an irregular pulse multiple times throughout the day in the background, without needing the user to actively engage the application,” Perez said.
Goals of the study
Each participant in the study is required to have an Apple Watch (series 1, 2 or 3) and an iPhone. An app on the phone intermittently checks the heart-rate pulse sensor for measurements of an irregular pulse. If sufficient episodes of an irregular pulse are detected, then the participant receives a notification and is asked to schedule a visit with a doctor involved in the study. Participants are then sent electrocardiography patches, which record the electrical rhythm of their hearts for up to a week. The goals of the study are threefold: to determine how many among those who receive irregular pulse notifications are found to have atrial fibrillation on ECG patch monitoring; to determine how many among those who received an irregular pulse notification go on to get medical attention; and to determine the accuracy of irregular-pulse detection by the watch by comparing it with the simultaneous ECG patch recordings.
“We now have access to high-quality sensors that can measure and detect changes in our bodies in entirely new and insightful ways without even needing to go to the doctor, but we need to rigorously evaluate them,” Turakhia said. “There’s never really been a study like this done before.”
A subset of the study data was used by Apple as part of its regulatory submission for FDA clearance of the smartwatch app that analyzes pulse-rate data. Apple Heart Study investigators were aware of the submission, but have not seen the submission data. “We are inspired by the overwhelming response to the Apple Heart Study,” said Sumbul Desai, MD, vice president of Apple. “Through the combined power of our participants, Apple Watch and Stanford Medicine, it’s one of the largest and most novel atrial fibrillation studies to date.”
Update: On March 18th, researchers from the Stanford University School of Medicine presented preliminary results of the Apple Heart Study, an unprecedented virtual study with over 400,000 enrolled participants. The researchers reported that wearable technology can safely identify heart rate irregularities that subsequent testing confirmed to be atrial fibrillation.
Key findings from the study include:
- Overall, only 0.5 percent of participants received irregular pulse notifications, an important finding given concerns about potential over-notification.
- 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 percent positive predictive value. Eighty-four percent of the time, participants who received irregular pulse notifications were found to be in atrial fibrillation at the time of the notification.
- One-third (34 percent) of the 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, it’s not surprising for it to go undetected in subsequent ECG patch monitoring.
- Fifty-seven percent of those who received irregular pulse notifications sought medical attention.
“The study’s findings have the potential to help patients and clinicians understand how devices like the Apple Watch can play a role in detecting conditions such as atrial fibrillation, a deadly and often undiagnosed disease,” said Turakhia. “The virtual design of this study also provides a strong foundation upon which future research can be conducted to explore the health implications of wearable technology.”
Marco Perez, added: “The performance and accuracy we observed in this study provides important information as we seek to understand the potential impact of wearable technology on the health system. Further research will help people make more informed health decisions.”