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).

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]
Popular Stories
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...
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...
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,...
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 ...
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...
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 ...
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...