Data suggest Apple Watch appropriate for AF screening, but not disease management
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Key takeaways:
- In adults with known atrial fibrillation, the Apple Watch had a low rate of false-positive detections and high specificity.
- Sensitivity for detection by participant and by AF episode was lower.
An Apple Watch feature designed to detect atrial fibrillation was associated with a low rate of false-positive detections but only modest sensitivity for detections in people with a history of AF, researchers reported.
The Apple Watch irregular rhythm notification feature uses photoplethysmography to identify prolonged episodes of irregular rhythm suggestive of AF. The technology is FDA-cleared for adults with no previous history of AF; however, these devices are increasingly being used for AF management.
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“Digital health technologies are powerful tools with great potential for the treatment of atrial fibrillation, but we are not at the point yet where we can use them in isolation to guide medical therapy,” Rod S. Passman, MD, MSCE, the Jules J. Reingold Professor of Electrophysiology at Northwestern University Feinberg School of Medicine and director of the Northwestern University Center for Arrhythmia Research, told Healio. “The intended use for the irregular rhythm notification algorithm on the Apple Watch is to detect AF in those without a known history of the arrhythmia; it should not be used to assess AF burden, efficacy of treatment or guide anticoagulation therapy.”
Increased sensitivity and wear times ‘may be necessary’
Passman and colleagues analyzed data from 30 adults from three hospital systems with a history of nonpermanent AF and either an insertable cardiac monitor (ICM) or cardiac implanted electronic device (CIED) with less than 5% ventricular pacing, enrolled between January 2020 and October 2021. Participants were fitted with an Apple Watch Series 5 and asked to wear the watch during waking hours for a minimum of 14 hours per day for 6 months. The mean age of participants was 65 years; 40% were women; 20 people had CIEDs.
Researchers compared AF episodes between the ICM/CIED and the irregular rhythm notification feature.
“Participants provided screen shots of all irregular rhythm notifications received during the study period and these episodes were compared to downloads from the patient’s ICMs/CIEDs,” the researchers wrote. “AF events detected by ICM/CIED without an associated irregular rhythm notification were further investigated by a screenshot of the participant’s ‘Activity’ page for the corresponding day. If the participant’s ‘Move’ bar graph was at zero during the time that the ICM/CIED detected an event, the participant was deemed to not be wearing their Apple Watch during this time.”
The primary endpoints were sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of the irregular rhythm notification by participant for AF greater than 1 hour. Secondary endpoints were sensitivity and positive predictive value by AF episode greater than 1 hour. Analysis was limited to a maximum of 10 ICM/CIED episodes per participant and included only those AF episodes occurring during active Apple Watch use confirmed by activity data.
Within the cohort, 11 participants had AF on ICM/CIED while wearing an Apple Watch, and eight of these were detected by the irregular rhythm notification. There were no false-positive irregular rhythm notification detections by participants (72% sensitivity; 100% specificity; 100% PPV; and 90% NPV).
Five participants had AF only when the Apple Watch was not worn. There were 70 AF episodes observed on ICM/CIED, 35 of which occurred while the Apple Watch was being worn. Of these, 21 were detected by irregular rhythm notification. There was one false positive.
The secondary endpoints of accuracy “by episode” during watch wear time were a sensitivity of 60% and a PPV of 95.5% for episodes lasting 1 hour or longer. The sensitivity for AF episodes lasting 1 to 12 hours and more than 12 hours was 58% and 75%, respectively (P = .635).
“The current irregular rhythm notification algorithm appears accurate for AF screening as currently indicated, but increased sensitivity and wear times may be necessary for disease management,” the researchers wrote.
Apple Watch research continues
Passman said the ongoing Rhythm Evaluation for Anticoagulation (REACT-AF) trial will compare current standard of care in people with a history of AF against a precision-targeted approach of time-delimited anticoagulation given for a brief period, guided by Apple Watch technology.
“Trials like the Heartline study will determine if screening the population for AF with this technology finds AF early and reduces stroke risk,” Passman told Healio. “Our REACT-AF trial will be using a highly sensitive AF detection feature on the Apple Watch to guide ‘pill in pocket’ anticoagulation to see if we can reduce exposure to anticoagulation while still protecting patients from stroke.”
For more information:
Rod S. Passman, MD, MSCE, can be reached at rod.passman@nm.org; Twitter: @passmanrod.
Perspective
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Oussama Wazni, MD
This study demonstrates that, if a patient has AF, sensitivity with the Apple Watch was 72%. That means there are 28% of AF cases that were not captured. When assessing AF episodes, it was only 60% sensitive. If patients are at low risk for stroke, the Apple Watch can work as a tool, but it still misses many patients who do have AF. The researchers do note that future iterations of the Apple Watch will likely be more sensitive, and indeed for AF episodes lasting more than 1 hour, it was much more sensitive.
The take-home message is the technology is improving. It is not yet medical grade for management of patients with diagnosed AF. I also would not rely on it for screening a population at high risk for AF, as it still misses some patients and some AF episodes.
This is an exciting time as technology keeps evolving. It is only going to get better. There will come a time when we can use technology like the Apple Watch for large populations with confidence that it is indeed accurate and providing reliable information.
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