With watchOS 5.1.2, Apple releases the ECG function on the Apple Watch Series 4 smartwatch. However, this works only with the models in the US and those that were bought in the US. The trick to simply switch the clocks in other countries to the US scheme worked only in the beta phase.
The ECG data is transmitted to the health app of the iPhone, which is connected to the watch. Apple says the accuracy of the ECG app has been confirmed in a clinical trial involving around 600 participants in the United States.
The ECG app will indicate if there are signs of atrial fibrillation, a severe form of cardiac arrhythmia, or a normal sinus rhythm in the wearer. The necessary electrodes are installed in the base of the watch and in the crown of the watch. The user must touch the crown with one finger to have the ECG measured, which takes about 30 seconds.
Regardless of the ECG, the Apple Watches are known to measure the pulse. The update to watchOS 5.1.2 also provides an update for older models: Users receive irregular heart rate notifications when five or more controls detect irregular heart rhythms over a minimum of 65 minutes.