Apple Watch identified atrial fibrillation in small group of users: study

Study data presented at the American College of Cardiology (ACC) annual meeting indicate that the Apple Watch was able to spot atrial fibrillation (AF) in certain wearers. In the study of 419 297 volunteers, 2161 people, or 0.5 percent of participants, received pulse notifications of irregular heart rhythms, while among 450 of these subjects who were included in a subsequent electrocardiogram (ECG) patch analysis, 34 percent were confirmed to have the condition.

Co-principal investigator Mintu Turakhia noted that AF "can come and go, particularly early on in the course of the disease," so it is "not surprising for it to go undetected in subsequent ECG patch monitoring." However, he cautioned that even though "only 34 percent of people…were still having [AF] on the ambulatory ECG, that doesn't mean that 66 percent didn't have [AF]." 

The Apple Heart Study consisted of volunteers with an Apple Watch and a compatible iPhone who self-enrolled in the trial. Eligible participants could not have AF nor be taking anticoagulants. If five of six repeat tachograms detected an irregular pulse within a 48-hour period, a notification was sent via the Heart Study app prompting participants to contact the study doctor for a video consultation to determine if the participant should wear an ECG patch. The patch was worn for up to seven days. The primary endpoints were detection of AF for more than 30 seconds on the ECG patch and simultaneous detection of AF on the ECG patch and tachogram. 

Other results from the study showed that notification rates were most frequent in volunteers over 65 years of age, at slightly more than 3 percent, compared with under 0.2 percent for those younger than 40.

Meanwhile, the positive predictive value for the notification was 84 percent, compared with 71 percent for tachograms. Further, approximately half of participants receiving an irregular pulse notification contacted a study doctor, but investigators said later surveys showed that 57 percent of participants who received a notification sought medical care outside the study regardless of whether they underwent a virtual consultation with a study doctor. 

The research team cautioned that the study lacked a control arm, and it did not monitor for outcomes such as stroke. Investigators also acknowledged that the target enrolment of 500 000 volunteers, including 75 000 people aged 65 and older, was not reached. 

Turakhia suggested the Apple Heart Study represents "a paradigm shift" for how clinical trials can be conducted, saying "we don't have to bring people into a brick and mortar clinic and give the study intervention." Meanwhile, editor-in-chief Kim Eagle said although the Apple Watch "offers promise," its accuracy is inferior to currently used monitoring techniques. "This is just a glimpse of the future, but we have a ways to go," Eagle remarked. 

Earlier this year, Johnson & Johnson announced an agreement with Apple to determine whether a new app-based heart health programme can speed diagnosis and improve outcomes in AF. Apple received de novo classification from the FDA of a new ECG feature on the Apple Watch last September. 

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