Apple Watch ECG: A guide to using the new atrial fibrillation monitor

We get to grips with Apple's potentially life-saving new feature

Apple made a splash earlier this year when it announced the Apple Watch Series 4 would have an ECG (electrocardiogram) monitor, and it's now available to use. It's capable of detecting irregular heart rhythms – a symptom of atrial fibrillation.

In that moment, the Apple Watch graduated from a fitness tracker to a potentially life-saving wearable and now, with the arrival of watchOS 5.1.2, that ECG feature has come alive.

That is, if you’re living in the US. Regulatory reasons mean the feature will take longer to roll out to other territories, including the UK. But we’ve been trying it out US-side, getting to grips with Apple’s new ECG feature.

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Apple Watch ECG: What’s it actually doing?

Before diving into the ins and outs of the Apple Watch ECG, let’s talk about what it’s even doing. In a nutshell, it’s monitoring the electrical patterns of your heartbeat. It does this using both the heart rate monitor on the underside of the Apple Watch and the Digital Crown, on which you’ll need to place a finger from the opposite hand. This lets the Watch monitor those beats across your heart.

Read this: What is atrial fibrillation?

The ECG is looking to see if the upper and lower chambers of your heart are in rhythm. If it detects that they're out of rhythm, this is known as atrial fibrillation. In a single 30 second test the Watch will be able to tell you if it think you're showing signs of AFib, but you'll need to perform the test several times to get a stronger indication.

Apple Watch ECG: How to set it up

Ok, first we'll talk you through the process of getting the feature going. First of all, you must have an Apple Watch Series 4. This is because the ECG feature requires the new Digital Crown to record the electrical pulses.

You’re going to first make sure your iPhone is updated to iOS 21.1.1, as this will bring your Health app up to date with the new feature. You’ll also need to update your Apple Watch to watchOS 5.1.2.

That's most of the work required. The next thing to do is to open up the Apple Health app on your phone. Assuming you've done the aforementioned updates, you'll get a prompt to set up the ECG. For this, all you need to do is enter your date of birth, then you'll be asked to take your first ECG reading.

How to take an Apple Watch ECG reading

After the initial setup is complete, you can take an ECG reading any time by going into the ECG app on the Apple Watch itself. Before you go any further, you want to make sure the watch is nice and snug to your wrist – not too tight – and then, ideally, rest your arm on something, even just your lap. That's what Apple advises, at least, though we've found that as long as you're reasonably still it has no problem getting a read.

Then all you need to do is touch your forefinger against the Digital Crown. You don't need to do this too hard, just enough that it's covering the entirety of the circle. You'll then see a graphic of your heart rate in real time and a timer counting down from 30 seconds. Let it do its thing.

Now, like us, you're likely to feel pretty anxious about suddenly getting a medical exam (didn't you buy this for the Instagram notifications?!). After 30 seconds the Watch will be able to give you the results:

Sinus rhythm: If everything is A-ok and your heart is beating in a uniform pattern between 50 and 100 BPM, you'll see 'Sinus rhythm' show up. Phew – but we'd still recommend doing it several times and turning on irregular rhythm notifications (we'll get to those in a moment).

Atrial fibrillation: This means the Watch has detected your heart is beating in an irregular pattern within those same heart rate boundaries. If you get this result, you should consult your doctor (you should also do the test several times).

Low or high heart rate: If your heart rate is higher than 100 BPM or lower than 50 BPM, the reading is deemed inconclusive. There are copious reasons for this; a high heart rate could come from exercise, stress or even alcohol, while a low one can come from intense training. If you do find your heart rate to be too low or high, you should find out why and, if necessary, consult a doctor.

Inconclusive: It's possible for the ECG app to deliver this result, which can arise from many things, including too much movement during the test or having the Watch too loose on your arm.

Setting up irregular rhythm notifications

Apple Watch ECG: A guide to using the new atrial fibrillation monitor

On top of taking deliberate readings, you can have the Apple Watch take occasional readings (usually in moments where you're still) to keep an eye for signs of AFib. While periodic checks are good, continual monitoring enables the Apple Watch to get a more comprehensive picture of how your heart is ticking along.

To set these up, go to Health Data in the app, tap on Heart, then scroll down to the bottom and tap on where it says Irregular Rhythm Notifications. You'll need to enter your date of birth again and tell the app whether you've been diagnosed with AFib before.

From then on, the Watch will monitor for signs of AFib, and if it detects symptoms on multiple occasions it'll send you a notification. But we need to point out that Apple's ECG technology isn't flawless, and the Watch cannot say for certain if you actually have AFib. Even when it's monitoring throughout the day, it isn't continuous. It also cannot detects signs of heart attacks, strokes or other heart conditions. Perhaps the Watch will be able to do these things and more one day, but right now they're not in the smartwatch's purview.

Still, it's mighty impressive what Apple has pulled off here, and something that's already proving to itself a potentially life-saving feature.

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