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On March 28, 2023, we reported on a study published in the Journal of Cardiovascular Electrophysiology that examined the accuracy of the Apple Watch Irregular Rhythm Notification (IRN) feature in persons with a previous diagnosis of nonpermanent atrial fibrillation (AF).
Researchers examined data from 30 adults from 3 hospital systems who had a history of nonpermanent AF and either an insertable cardiac monitor (ICM) or cardiac implanted electronic device (CIED) with <5% ventricular pacing. 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 and 40% were women. Among the cohort, 10 persons had ICMs and 20 had CIEDs. Investigators compared AF episodes between the ICM/CIED and IRN feature.
The primary endpoints were sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the IRN by subject for AF ≥1 hour. Secondary endpoints were sensitivity and PPV by AF episode ≥1 hour. Analysis was limited to a maximum of 10 ICM/CIED episodes per participant and included only AF episodes that occurred during active Apple Watch use confirmed by activity data.
Among the cohort, 11 had AF on ICM/CIED while wearing an Apple Watch, of whom 8 were detected by IRN. There were no false-positive IRN 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 subject was wearing an Apple Watch. Of these, 21 were detected by IRN with 1 false positive. Therefore, according to researchers, the secondary endpoints of accuracy “by episode” during watch wear time were a sensitivity of 60% and a PPV of 95.5% for AF episodes lasting ≥1 hour.
Note from authors
"In a population with known AF, the AW [Apple Watch] IRN had a low rate of false positive detections and high specificity for subjects with AF. Sensitivity for detection by subject and by AF episode was lower. The current IRN algorithm appears accurate for AF screening as currently indicated, but increased sensitivity and wear times may be necessary for disease management."