Apple has designed a new algorithm that Apple Watch uses to measure electrocardiogram (ECG) waves, according to developer documentation for the iOS 14.3 and watchOS 7.2 betas.
In the official documentation, a new "version 2 algorithm" declaration has been added. No other information is included.
The ECG feature includes irregular heart rhythm detection, which intermittently measures the user's heart rate in the background and sends a notification if it detects an anomaly it categorizes as atrial fibrillation, which can be a serious heart arrhythmia condition.
Based on beta code uncovered by MacRumors, it's likely that the new algorithm will allow the ECG app to check for atrial fibrillation (AFib) at higher heart rates - during exercise, for example.
iOS 14.3 will introduce support for Apple Fitness+, Apple's upcoming fitness service that will work with the Apple Watch, plus it brings a new Cardio Fitness feature that lets you know if your VO2Max levels are low. VO2Max is a useful measurement of overall fitness and heart health.
iOS 14.3 is set to be released on Monday, December 14, which is also the day that Apple Fitness+ is coming out.
Wednesday September 9, 2026 9:10 am PDT by Jordan Golson
Apple's "Surprise and Shine" event kicks off today at 10:00 a.m. Pacific Time, where we're expecting to see the foldable iPhone Duo, the iPhone 18 Pro and Pro Max, Apple Watch Series 12 and Ultra 4 models, new AirPods 5 earphones, and perhaps some other announcements.
Apple is providing a live video stream on its website, on YouTube, and in the company's TV app across various platforms. We...
Bloomberg's Mark Gurman today further outlined what to expect from the Apple Watch Series 12 and Apple Watch Ultra 4 set to be unveiled on September 9.
While it was initially rumored that Touch ID may be coming to the Apple Watch this year, Gurman reiterated that he does not expect the Series 12 or Ultra 4 to have any major design changes compared to the current Series 11 and Ultra 3 models.
...
Tuesday September 8, 2026 10:24 am PDT by Tim Hardwick
Apple's biggest event of the year is almost here, and all eyes are on Cupertino. With the first foldable iPhone expected to headline Apple's "Surprise and Shine" event on Wednesday, September 9, at 10:00 a.m. Pacific Time, the rumor mill has been running full throttle, fuelled by the biggest single design change in the life of the iPhone.
To get you up to speed, here's a quick reference...
Wait what? The ECG only works when your finger is on the Digital Crown. It can’t work in the background.
The background irregular heart rhythm detection does not use the ECG but it is grouped with the ECG features (which is technically inaccurate but they are related features, just different technologies). It's been around as long as the ECG: "Using the optical heart sensor in Apple Watch Series 1 or later, the irregular rhythm notification feature will occasionally check the user’s heart rhythm in the background for signs of an irregular heart rhythm that appears to be AFib and alerts the user with a notification if an irregular rhythm is detected on five rhythm checks over a minimum of 65 minutes." (https://www.apple.com/newsroom/2018/12/ecg-app-and-irregular-heart-rhythm-notification-available-today-on-apple-watch/)
Still waiting for ECG in Japan! Any news about it?
Since ECG received final medical approval in Japan this September, I guess maybe iOS 14.3 will cover ECG functionality also Japan as well? *finger-crossed*
