Apple Watch Able to Detect Abnormal Heart Rhythm With 97% Accuracy

The Apple Watch's built-in heart rate monitor is 97 percent accurate when detecting the most common form of an abnormal heart rhythm when paired with an algorithm to sort through the data, according to a new study conducted by the University of California, San Francisco and the team behind the Cardiogram app (via TechCrunch).

There were 6,158 participants in the study, all of whom used the Cardiogram app on the Apple Watch to monitor their heart rate. Most were known to have normal EKG readings, but 200 suffer from paroxysmal atrial fibrillation (an occasional irregular heartbeat).

cardiogramalgorithm
Data from these participants, along with data taken from normal Cardiogram users, was used to build a neural network that could recognize the abnormal heart rhythms solely from data collected by the Apple Watch. As of today, Cardiogram says its algorithm can almost always successfully determine when a patient is in atrial fibrillation.

In order to validate the model, we obtained gold-standard labels of atrial fibrillation from cardioversions. In a cardioversion, a patient experiencing atrial fibrillation is converted back to normal sinus rhythm, either chemically or with a shock to the heart. 51 patients at UCSF agreed to wear an Apple Watch during their cardioversion.

We obtained heart rate samples before the procedure, when the patient was in atrial fibrillation, and after, when patient's heart was restored to a normal rhythm. On this validation set, our model performed with an AUC of 0.97, beating existing methods.

Cardiogram is a startup that's aiming to garner more information from the data collected by the Apple Watch. The study, which Cardiogram has raised funding for, started in March of 2016 and will continue as UCSF and Cardiogram work to refine the neural network and detect other conditions beyond atrial fibrillation.

Cardiogram plans to put in additional work before using its algorithm to start notifying Cardiogram users of arrhythmias. The company needs to conduct further testing to make sure the algorithm works in a variety of conditions and it needs to work on scaling it so it can be used continuously by all Cardiogram users.

The Cardiogram app can be downloaded from the App Store for free. [Direct Link]

Related Roundup: Apple Watch 10
Buyer's Guide: Apple Watch (Neutral)

Popular Stories

iOS 19 Mock WWDC25 Feature

iOS 19 Expected to Run on These iPhones

Monday March 31, 2025 5:28 pm PDT by
iOS 19 will not be available on the iPhone XR, iPhone XS, or the iPhone XS Max, according a private account on social media site X that has accurately provided information on device compatibility in the past. The iPhone XR, iPhone XS, and iPhone XS Max all have an A12 Bionic chip, so it looks like iOS 19 will discontinue support for that chip. All other iPhones that run iOS 18 are expected...
maxresdefault

Apple Releases iOS 18.4 With Priority Notifications, Ambient Music, New Emoji and More

Monday March 31, 2025 10:03 am PDT by
Apple today released iOS 18.4 and iPadOS 18.4, the fourth major updates to the iOS 18 and iPadOS 18 operating system updates that came out last year. iOS 18.4 and iPadOS 18.4 come two months after Apple released iOS 18.3 and iPadOS 18.3. Subscribe to the MacRumors YouTube channel for more videos. The new software can be downloaded on eligible iPhones and iPads over-the-air by going to...
watchOS 11 Thumb 2 1

Apple Releases watchOS 11.4 With Sleep Alarm Update

Tuesday April 1, 2025 10:34 am PDT by
Apple today released watchOS 11.4, the fourth major update to the operating system that runs on the Apple Watch. watchOS 11.4 is compatible with the Apple Watch Series 6 and later, all Apple Watch Ultra models, and the Apple Watch SE 2. watchOS 11.4 can be downloaded on a connected iPhone by opening up the Apple Watch app and going to General > Software Update. To install the new software,...
AirPods Pro Firmware Feature

Apple Releases New Firmware for AirPods Pro 2 and AirPods 4

Monday March 31, 2025 11:27 am PDT by
Apple today released new firmware updates for all AirPods 4 and AirPods Pro 2 models. The new firmware is version 7E93, up from the 7B21 firmware that was installed on the AirPods Pro 2 and the 7B20 firmware available on the AirPods 4 and AirPods 4 with ANC. It is not immediately clear what new features or changes are included in the new firmware, but we'll update this article should we find ...
macOS Sequoia Feature

Apple Releases macOS Sequoia 15.4 With Mail Categorization and More

Monday March 31, 2025 10:04 am PDT by
Apple today released macOS Sequoia 15.4, the fourth major update to the macOS Sequoia operating system that launched in September. macOS Sequoia 15.4 comes two months after the launch of macOS Sequoia 15.3. Mac users can download the ‌‌macOS Sequoia‌‌ update through the Software Update section of System Settings. It is available for free on all Macs able to run macOS 15. With...
iPhone 17 Pro 34ths Perspective

iPhone 17 Pro Launching Later This Year With These 10 New Features

Sunday March 23, 2025 10:00 am PDT by
While the iPhone 17 Pro and iPhone 17 Pro Max are not expected to launch until September, there are already plenty of rumors about the devices. Below, we recap key changes rumored for the iPhone 17 Pro models as of March 2025: Aluminum frame: iPhone 17 Pro models are rumored to have an aluminum frame, whereas the iPhone 15 Pro and iPhone 16 Pro models have a titanium frame, and the iPhone ...
Apple Card iPhone 16 Pro Feature

Visa and American Express Vying to Win Apple Card Deal in 'Fierce' Fight

Tuesday April 1, 2025 1:50 pm PDT by
Visa wants to pay Apple approximately $100 million to be the new payment network for the Apple Card, reports The Wall Street Journal. As of right now, the Apple Card is on the Mastercard payment network, but that is set to change because Apple is ending its partnership with Goldman Sachs. Both American Express and Visa are vying to replace Mastercard as Apple's card services provider, while...

Top Rated Comments

PBRsg Avatar
103 months ago
You can program it to delete your browser history if it detects that you are about to die.
Score: 36 Votes (Like | Disagree)
heimo Avatar
103 months ago
Siri: "Looks like you're having a heart attack"
Me: "Call an ambulance"
Siri: "I'm sorry, Dave. I'm afraid I can't do that."
Score: 26 Votes (Like | Disagree)
JaySoul Avatar
103 months ago
Potentially awesome.

I think a lot of people are waiting on two big things:

1) Really accurate heart-rate monitoring (getting there)

2) Blood sugar analysis for diabetics.

I have a feeling Apple will get there within a decade, fingers crossed.
Score: 19 Votes (Like | Disagree)
brandonballinger Avatar
103 months ago
It'll be a long time before this comes to market. And from what it looks like, Apple doesn't want to have to go through the hassle of FDA approval for its devices.
(Cardiogram co-founder here)

The Cardiogram app itself is already on the app store (https://itunes.apple.com/us/app/cardiogram/id1000017994?ls=1&mt=8) and the deep learning to screen for conditions are coming sooner than you might think. :)
Score: 18 Votes (Like | Disagree)
brandonballinger Avatar
103 months ago
does this work with series 1 too? Looking into buying one soon.
(Cardiogram developer here) Yes—we're compatible with all Apple Watch hardware as long as you're on watchOS 3.
[doublepost=1494535132][/doublepost]
Using a device (A-watch) to tell you when you're heart is skipping beats is like having a device to tell you when you're getting cramps. Every missed heart beat is is easily felt and unpleasant enough as it is without some damn device reminding you of it.
Atrial fibrillation is often asymptomatic—Circulation (the top cardiology journal) just published a big report on the evidence for device-based screening of AF:
circ.ahajournals.org/content/135/19/1851.full?ijkey=StzSPk8eljGaP2G&keytype=ref
Score: 17 Votes (Like | Disagree)
RosieQ Avatar
103 months ago
I'm an Emergency doctor at UCSF and this could be super useful. We regularly get patients coming to the hospital with atrial fibrillation, and while some swear they know exactly when it started several studies have shown that this just isn't all that successful. Current guidelines allow for electrical cardioversion within 24 hours of onset of atrial fibrillation. If the onset is unknown we have to place a patient on long term anticoagulation (expensive and risk of bleeding with trauma) or do an invasive heart ultrasound with anticoagulation for a few days prior to cardioversion. If we were able to look back at app data/ heart rate monitoring this could save patients and the system a lot of money and time! Glad to see my home institution doing such great work.
Score: 13 Votes (Like | Disagree)