Apple Watch owners may be able to use a dedicated ECG app to obtain a more detailed picture of their heart rhythm than the watch’s standard heart-rate tracking provides. The feature records electrical signals from the heart and can flag certain irregular rhythms, but it is not intended to diagnose heart attacks or replace urgent medical care.

The ECG app is available on Apple Watch Series 4 and later, excluding SE models, as well as all Ultra models, subject to local availability and current iOS and watchOS software. Users set it up through the iPhone Health app, then hold a finger on the Digital Crown for 30 seconds while wearing the watch snugly; results can include sinus rhythm, indicating a uniform rhythm between 50 and 100 beats per minute at the time of measurement, or atrial fibrillation, indicating an irregular rhythm.