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

Get to grips with Apple's potentially life-saving health feature

Apple took a big step into health monitoring with the Apple Watch Series 4, as the smartwatch became the first to feature the capability of giving an ECG reading – or EKG, if you prefer.

Now your everyday Apple Watch is armed with the ability to detect irregular heart rhythms – a symptom of atrial fibrillation – and has graduated from fitness tracker to potentially life-saving tech. After coming to the US first, the ECG app is now also rolling out to the UK and 18 other countries.

Read next: Complete guide to the Apple Watch heart monitor

Regulatory reasons mean the feature still isn't in every territory where the Series 4 is sold, but we’ve been trying it out in the US and UK and getting to grips with Apple’s latest heart rate feature. Read on for everything you need to know.

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Apple Watch ECG: What is it?

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.

Hold up: 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

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 need to make sure your iPhone is updated to the latest version of iOS, as this will bring your Health app up to date with the new feature. You’ll also need to update your Apple Watch to the latest version of watchOS.

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

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

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 index finger 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, though, the Watch will be able to give you the results.

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

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 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.

Apple Watch ECG: Is it accurate?

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

Since Tim Cook stood on stage and announced the arrival of the ECG app, cardiologists, analysts and everybody in between have speculated about just how accurate it is at detecting irregular rhythms. After all, this kind of thing would usually be reserved for professional equipment handled by, well, medical professionals – not a tech company.

Apple has acknowledged it's got plenty to do before the feature fully reaches its potential, and has just recently published the results of its related Apple Heart Study (spoiler alert: things are promising, but still too limited), which Stanford University also had a hand in.

The real answer: It's impossible to know exactly how accurate it is, but it's probably accurate enough. Why? Well, to get clearance from the FDA in the US and then the CE mark for use in the EEA, it has to meet a certain bar of accuracy. And during testing of 600 subjects in a controlled environment, the Watch was able to accurately detect the sinus rhythm classification with 99.6% accuracy, and reach the AFib classification with 98.3% accuracy.

The technology isn't flawless, and the Watch can't say for certain if you actually have AFib. Even when it's monitoring throughout the day, it isn't continuous. It also can't 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 so far, and something that's already proving to itself a potentially life-saving feature.




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