Apple Watch ECG readings

Apple Watch Series 4 is getting the hotly anticipated ECG feature today. The ECG app will appear for customers using Apple Watch in the United States, after updating to watchOS 5.1.2 (releasing later today). The 5.1.2 update will also include irregular heart rate notifications for Apple Watch Series 1 through Series 4.

To take an ECG, users simply place their finger on the digital crown and wait for 30 seconds whilst the Watch scans the electrical impulses in your finger.

Apple made a lot of fanfare out of the ECG feature when it unveiled the Series 4 watch back in September. It touted that Apple Watch was the first device to receive FDA clearance for over-the-counter ECG features. However, the app was not available at launch and promised to come later this year.

Today, Apple is making good on its promise. The ECG app requires the Series 4 hardware as it uses electrodes in the back crystal and the Digital Crown to function. With two contact points, Apple Watch can generate the equivalent of a single-lead medical ECG.

The accuracy of the Watch will obviously not be as good as real medical equipment, but it is by no means frivolous. Apple says it validated the ECG’s accuracy in a clinical trial of 600 participants:

The ECG app’s ability to accurately classify an ECG recording into AFib and sinus rhythm was validated in a clinical trial of around 600 participants. Rhythm classification from a gold standard 12-lead ECG by a cardiologist was compared to the rhythm classification of a simultaneously collected ECG from the ECG app. The study found the ECG app on Apple Watch demonstrated 98.3 percent sensitivity in classifying AFib and 99.6 percent specificity in classifying sinus rhythm in classifiable recordings. In the study, 87.8 percent of recordings could be classified by the ECG app.

As part of initial setup, users will be instructed about how to interpret results provided by the Watch and what the features can and cannot do.

When an ECG session is conducted, the watch will tell you if it senses normal sinus rhythm or detects signs of atrial fibrillation. The full electriocardiogram chart can be exported as PDF in the Health app, to send to your doctor.

The irregular heart rate rhythm notifications will be available for Series 1, Series 2, Series 3 and Series 4 watches. The watch will passively track heart rate rhythms in the background and push a notification if it believes something is wrong. The user can then conduct an ECG in the ECG app and/or contact their doctor for further diagnosis.

You can see a video demo of the ECG app in action in this video by CBS This Morning, including a short interview with Apple COO Jeff Williams.

Both of these features will be gated to the United States region due to legal restrictions. Expect to see watchOS 5.1.2 available to install later today. The update also includes a Control Center toggle for Walkie-Talkie.

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About the Author

Benjamin Mayo

Benjamin develops iOS apps professionally and covers Apple news and rumors for 9to5Mac. Listen to Benjamin, every week, on the Happy Hour podcast. Check out his personal blog. Message Benjamin over email or Twitter.