By Matthew E. Fink, MD
Louis and Gertrude Feil Professor and Chair, Department of Neurology, Associate Dean for Clinical Affairs, NYP/Weill Cornell Medical College
Dr. Fink reports no financial relationships relevant to this field of study.
Perez MV, Mahaffey KW, Hedlin H, et al, for the Apple Heart Investigators. Large-scale assessment of a smartwatch to identify atrial fibrillation. N Engl J Med 2019;381:1909-1917.
I just bought a new Apple watch, and as I was setting it up, it asked me if I would like to register with Apple to receive notification if my watch picked up an abnormal heart rhythm. What should I do?
The Apple Heart Study Investigators published their initial findings recently, and their report may give us more information that can help answer the question. The study participants were people without atrial fibrillation who purchased a smart phone app and consented to monitoring using a smartwatch-based irregular pulse notification algorithm, which identified possible atrial fibrillation. If notification occurred, the person was mailed an electrocardiography (ECG) patch to be worn for seven days to confirm the findings first identified by the smartwatch. Participants were surveyed 90 days after notification of irregular pulse and at the end of the study. The main objectives were to estimate the proportion of notified participants with atrial fibrillation diagnosed by an ECG patch, and the positive predictive value of a smartwatch identifying an irregular pulse.
The investigators recruited 419,297 participants in less than a year and participants were monitored over a median of 117 days. A total of 2,161 participants (0.52%) received notifications of irregular pulse. Of the 450 participants who returned their ECG patches containing data for analysis, atrial fibrillation was identified in 34%, overall. In participants 65 years of age or older, atrial fibrillation was present in 35%. The positive predictive value for observing atrial fibrillation after an irregular pulse notification from a smartwatch, was 0.84. Of the 1,376 notified participants who returned a survey, 57% contacted their own healthcare providers outside of the study.
The age distribution of this group is different than the usual cohort at risk for atrial fibrillation: 52% were between the ages of 22 and 39 years of age, and only 5.9% were 65 years or older. The group that purchased and wore smartwatches were considerably younger than patients at risk for atrial fibrillation or stroke. Therefore, the overall rate of notification, about one half of 1%, is quite low but applies largely to a healthy cohort of young people. A much more useful study would have included an older cohort that carries a higher risk of atrial fibrillation. What do we do with several hundred young people who had an irregular heart rate picked up by the smartwatch, but are otherwise in excellent health? Do we subject them to an expensive cardiac evaluation? Is this study good for the people who were being monitored, or is it good for Apple to encourage people to buy their smartwatch?
What should I do? Well, since I am in the over-65 age group, and my mother had atrial fibrillation, I will sign up and become a participant.
