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Over 2,000 Participants Received Irregular Heart Rhythm Notification in Apple Watch Study

Stanford Medicine researchers presented their findings of the Apple Heart Study at the American College of Cardiology's 68th Annual Scientific Session and Expo in New Orleans today, as noted by Apple in a press release.


Apple and Stanford created the study to evaluate the Apple Watch's irregular heart rhythm notification feature, which occasionally checks the wearer's heart rhythm in the background and sends a notification if an irregular heart rhythm appears to be suggestive of atrial fibrillation.

419,093 people across the United States participated in the study. As part of the study, if an irregular heart rhythm was identified, participants received a notification on their Apple Watch and iPhone, a phone consultation with a doctor, and an ECG patch for additional monitoring.

Study results showed 0.5 percent of participants - approximately 2,095 people - received an irregular heart rhythm notification. Apple says "many participants sought medical advice following their irregular rhythm notification."

Apple COO Jeff Williams:
We are proud to work with Stanford Medicine as they conduct this important research and look forward to learning more about the impact of Apple Watch alongside the medical community. We hope consumers will continue to gain useful and actionable information about their heart health through Apple Watch.
Apple announced the Heart Study in collaboration with Stanford back in November 2017 and stopped accepting new participants in August 2018.

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Top Rated Comments

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26 weeks ago
So what did this lead to? 0.5% got the notification and then what? Did they all really have irregular heart rhythm or were there false positives?
Rating: 31 Votes
26 weeks ago
A couple times a month I get a few dropped heartbeats and some fluttering around for a bit while I wonder if this is finally it. But every time, it ends in disappointment. I still have to get up the next day and go to work to prop up this barbaric culture for absolutely no good reason.
Rating: 18 Votes
26 weeks ago
No medical screening test is 100% accurate. Early pregnancy tests are about 99% accurate. Even mammogram screening for breast cancer is only 87% accurate https://ww5.komen.org/BreastCancer/AccuracyofMammograms.html

Most people in the medical community agree it is better to have a false positive than a false negative because a false negative would discourage someone from seeking medical treatment and could ultimately lead to worse effects than someone seeking medical treatment for a condition they do not have.

For such a new, low cost, and non-intrusive device, I think the results of this study are actually pretty amazing.
Rating: 12 Votes
26 weeks ago
Irregular rhythm happens everyday, even by narrow medical definition; there is variation even with breathing.

The irregularity detected here is reported "if an irregular heart rhythm appears to be suggestive of atrial fibrillation." The software is setup by a medical team with oversight to eliminate the daily variations - A Fib is characteristically different. Even on a 12-lead ECG with Holter monitoring, the interpretation is physician based, preferably a cardiologist.

So, if 200-20 or even 2 of these detected were found with real atrial fibrillation rhythm, it is a win; these are from people with no known heart problems.

The worst a false positive does is send someone for further rhythm monitoring by a pro - worth the hassle.

The first post is sarcasm.
Rating: 11 Votes
26 weeks ago

So what did this lead to? 0.5% got the notification and then what? Did they all really have irregular heart rhythm or were there false positives?


I enrolled on the first day that the AHS app was available to the public. From the app, I had 3,144 data contributions in 459 days. As info, I cycled about 6,000 miles during that period, probably about half those days. My heart rate normally goes way up when cycling. RHR tends to be kind of low. I received an "Irregular Heart Rhythm Observed" notification about 45 days into the study:

* I initiated an in-app video call to an AHS cardiologist using the direct link on the notification that popped up. She interviewed me for about 30 minutes. During the interview, she discussed the study as having flagged me for single digit number of SVT events during five different 60-second measurement periods. (Supra-ventricular Tachycardia)
* They overnighted a 7-day ambulatory ECG monitor that I returned at the end of the week.
* When the results were ready, they notified me and sent another in-app video call link.
* A second video conference explained the results -- a few more instances of SVT detected. She recommended that I follow-up with a cardiologist, who was provided the monitor results. I also got pdfs of all records.
* I went to a locally recommended cardiologist, who discussed the SVT events that the watch and monitor picked up.
* He recommended I have an echocardiogram done to establish a baseline, which I did.
* There was a follow-up to discuss the results.

I guess it wasn't a false positive and it wasn't A-fib. The cardiologist seemed surprised that a fitness tracker caught it.
Rating: 9 Votes
26 weeks ago

So what did this lead to? 0.5% got the notification and then what? Did they all really have irregular heart rhythm or were there false positives?


34% were confirmed to have atrial fibrillation with a follow-up.

Not all the other 66% would be false positive since it's an intermittent condition.
Rating: 9 Votes
26 weeks ago

So what did this lead to? 0.5% got the notification and then what? Did they all really have irregular heart rhythm or were there false positives?


This sounds like you are interested in actual science instead of cherry picked statistics to put in a headline... ;)
Rating: 8 Votes
26 weeks ago
Without having the entire study group have an EKG afterwards there’s no way to measure the actual effectiveness of the watch. Of course if even just one life is saved it’s great but I feel Apple is being a little disingenuous here.
Rating: 7 Votes
26 weeks ago

So what did this lead to? 0.5% got the notification and then what? Did they all really have irregular heart rhythm or were there false positives?

In my case, the fact I had an Apple Watch saved my life. I was asked if I wanted to join the study. Why not I did not think twice about it, I gave my permission and that was it.

One morning I walked my dog and I felt anxious and a bit out of breath. I decided to rest, read a book. A while later I got a message that stated something like this “your pulse rate has been 41 for the past 2 hours, you may want to check with your doctor in case there might be a problem”. It was Sunday, I figured I would call her the next day. Nevertheless, I called the weekend service and the nurse answered. I told her my watch told me to check with my doctor. Who? I read the message to her, she asked a couple of questions, asked if I was alone.
She told me to stay where I was and she would send someone to help me. A few minutes later two fire trucks and an ambulance were at my door.

The emergency room's question was again, what, who? In a few minutes 4 doctors and a cardiologist asked me again what made me call. They explained that the top of my heart had stopped connecting with the bottom part.
After waiting for a long time in the emergency room I wrote to Tim Cook to thank him. A couple of hours later I received his reply.

Early in the morning I had an operation and they implanted a cardio messenger to alert them of any complications.

So, yes I’ll be first in line when the new Apple Watch comes out.
Rating: 7 Votes
26 weeks ago

Irregular rhythm happens everyday, even by narrow medical definition; there is variation even with breathing.

The irregularity detected here is reported "if an irregular heart rhythm appears to be suggestive of atrial fibrillation." The software is setup by a medical team with oversight to eliminate the daily variations - A Fib is characteristically different. Even on a 12-lead ECG with Holter monitoring, the interpretation is physician based, preferably a cardiologist.

So, if 200-20 or even 2 of these detected were found with real atrial fibrillation rhythm, it is a win; these are from people with no known heart problems.

The worst a false positive does id send someone for further rhythm monitoring by a pro - worth the hassle.

The first post is sarcasm.

Key findings....very interesting as it shows the AW EKG can have a positive impact on health by predicting potential medical events.


* Overall, only 0.5 percent of participants received irregular pulse notifications, an important finding given concerns about potential over-notification.
* Comparisons between irregular pulse-detection on Apple Watch and simultaneous electrocardiography patch recordings showed the pulse detection algorithm (indicating a positive tachogram reading) has a 71 percent positive predictive value. Eighty-four percent of the time, participants who received irregular pulse notifications were found to be in atrial fibrillation at the time of the notification.
* One-third (34 percent) of the participants who received irregular pulse notifications and followed up by using an ECG patch over a week later were found to have atrial fibrillation. Since atrial fibrillation is an intermittent condition, it’s not surprising for it to go undetected in subsequent ECG patch monitoring.
* Fifty-seven percent of those who received irregular pulse notifications sought medical attention.
Rating: 6 Votes

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