Apple Watch study to identify AF in today’s New England Journal of Medicine

[Squaresloane]

Large-Scale Assessment of a Smartwatch to Identify Atrial Fibrillation

List of authors.

Marco V. Perez, M.D., Kenneth W. Mahaffey, M.D., Haley Hedlin, Ph.D., John S. Rumsfeld, M.D., Ph.D., Ariadna Garcia, M.S., Todd Ferris, M.D., Vidhya Balasubramanian, M.S., Andrea M. Russo, M.D., Amol Rajmane, M.D., Lauren Cheung, M.D., Grace Hung, M.S., Justin Lee, M.P.H., et al., for the Apple Heart Study Investigators*

November 14, 2019

N Engl J Med 2019; 381:1909-1917

DOI: 10.1056/NEJMoa1901183

Abstract

BACKGROUND

Optical sensors on wearable devices can detect irregular pulses. The ability of a smartwatch application (app) to identify atrial fibrillation during typical use is unknown.

METHODS

Participants without atrial fibrillation (as reported by the participants themselves) used a smartphone (Apple iPhone) app to consent to monitoring. If a smartwatch-based irregular pulse notification algorithm identified possible atrial fibrillation, a telemedicine visit was initiated and an electrocardiography (ECG) patch was mailed to the participant, to be worn for up to 7 days. Surveys were administered 90 days after notification of the irregular pulse and at the end of the study. The main objectives were to estimate the proportion of notified participants with atrial fibrillation shown on an ECG patch and the positive predictive value of irregular pulse intervals with a targeted confidence interval width of 0.10.

RESULTS

We recruited 419,297 participants over 8 months. Over a median of 117 days of monitoring, 2161 participants (0.52%) received notifications of irregular pulse. Among the 450 participants who returned ECG patches containing data that could be analyzed — which had been applied, on average, 13 days after notification — atrial fibrillation was present in 34% (97.5% confidence interval [CI], 29 to 39) overall and in 35% (97.5% CI, 27 to 43) of participants 65 years of age or older. Among participants who were notified of an irregular pulse, the positive predictive value was 0.84 (95% CI, 0.76 to 0.92) for observing atrial fibrillation on the ECG simultaneously with a subsequent irregular pulse notification and 0.71 (97.5% CI, 0.69 to 0.74) for observing atrial fibrillation on the ECG simultaneously with a subsequent irregular tachogram. Of 1376 notified participants who returned a 90-day survey, 57% contacted health care providers outside the study. There were no reports of serious app-related adverse events.

CONCLUSIONS

The probability of receiving an irregular pulse notification was low. Among participants who received notification of an irregular pulse, 34% had atrial fibrillation on subsequent ECG patch readings and 84% of notifications were concordant with atrial fibrillation. This siteless (no on-site visits were required for the participants), pragmatic study design provides a foundation for large-scale pragmatic studies in which outcomes or adherence can be reliably assessed with user-owned devices. (Funded by Apple; Apple Heart Study ClinicalTrials.gov number, NCT03335800. opens in new tab.)

[BobD Volunteer]

Those of us who attended Patients Day this year will have seen a presentation on technology where the Apple watch and otpical system was discussed. The limitation is that it is not autonomous and requires the wearer to trigger an event record so obvioulsy has limitations. The gold standard if ever achieved will be recording without wearer's action day or night to enable ALL events to be noted. I think currently only Holter (plus Ziopatch) and implantable loop recorder can do this.

[Squaresloane in reply to BobD]

Thanks for the insight Bob - the participation of an engaged patient can optimise the outcome for many medical conditions. That includes participation in this forum.

[Gincalpe]

Thanks - as BobD says the limitation of the watch is you have to press the button to get an ECG so it only captures that moment. A Kardia does the same for a lot less money. For those who suffer with PAF it can be used to record an episode.

[Squaresloane in reply to Gincalpe]

Thanks Gincalpe - the research described in the paper doesn’t discuss other recording options. Maybe another research group will do that. Whatever the health issue, big data can lead to improvements in treatment pathways.

[AFAnswerseeker]

Hi All - I agree with the above but what i have found useful on the iwatch is that it notifies me if my heart rate is high without exercise being detected - i can then manually take the ECG on my wrist.