The most interesting feature of the Apple Watch 4 is probably its ability to take electrocardiogram (ECG) readings. This is done using electrodes built into the Digital Crown and the case back. Apple showed this off at the Watch’s launch event in September but while the hardware to take ECGs has always been there, Apple has yet to launch the necessary software to do it.
That changes today however as the US is now the first country to get the ECG software as part of watchOS 5.1.2. Apple is also rolling out an irregular rate notification feature that will be available on all Apple Watch models going back to Series 1.
The irregular heart rate monitoring is passive and Apple says that it checks your rhythm every two hours or so (depending on whether you’re stationary or not), and if there are five consecutive readings that seem abnormal, it will alert you and suggest you reach out to a doctor.
However, for now at least, both ECG and irregular heart rate monitoring are only rolling out in the US, and it’s unclear if ECG will ever be available in other countries. Even though Apple states that the Watch 4 is not a diagnostic tool, health features, especially complicated ones like ECG readings, require necessary clearance from various regulatory health bodies. According to 9to5mac it could take “years” for Apple to get ECG approval in other countries.