One of the major new features of the Apple Watch Series 4 is its electrocardiogram (ECG)support, letting you capture your heart rhythm with your smartwatch. And starting today, that feature is rolling out to users.

Apple is rolling out the watchOS 5.1.2 update today, complete with the ECG support for Apple Watch Series 4 owners. Just launch the ECG app and hold your finger on the Digital Crown to complete the circuit and measure electrical signals across your heart. After 30 seconds, your heart rhythm will be classised as AFib, sinus rhythm, or inconclusive, and the results will be saved in your iPhone's Health app and can be shared with physicians as a PDF.

Also coming with the watchOS 5.1.2 update is the irregular heart rhythm notification. Available on Apple Watch Series 1 and later, the watch will occasionally check your heart rhythm in the background for signs of an irregular heart rhythm that could be AFib. If it detects five rhythm checks over a minimum of 65 minutes, your watch will alert you.

These new heart features are available in the U.S., Puerto Rico, Guam, and the U.S. Virgin Islands to start.