Everything you need to know about using Apple's life-saving heart health feature
Apple Watch introduced electrocardiogram (ECG) heart measurements in 2018 with Series 4, allowing users to easily monitor their heart rhythm.
Available on compatible Apple Watch models, including Series 4 and later (excluding Apple Watch SE), the ECG app provides users with information about their heart rhythm using a feature that has FDA clearance in the US.
The 30-second test may help identify signs of an irregular heart rhythm that could be consistent with atrial fibrillation (AFib). AFib is a condition that causes an irregular heart rhythm and can sometimes lead to a rapid heartbeat.
And it shouldn’t be overlooked. “AFib increases the risk of stroke, heart failure, and other heart-related complications,” according to the Mayo Clinic.
That’s the basic overview, but there’s a lot more to understand about how the Apple Watch ECG app functions on your wrist.
In this guide, we’ll cover all the details of the heart health feature, including research on its performance compared with clinical ECG testing and how to set it up.
What is an ECG measurement?
An ECG reading records the heart’s electrical activity over a short period. Typically, this is done with a clinical ECG machine, although Apple has incorporated this functionality into compatible smartwatches, such as Apple Watch Series 10.
It does this by using electrodes on the underside of Apple Watch and the Digital Crown, where users need to place a finger from the opposite hand. This creates a circuit that allows the watch to record electrical signals related to heart rhythm.
The ECG analysis evaluates heart rhythm patterns and looks for signs consistent with atrial fibrillation (AFib). If an irregular rhythm consistent with AFib is detected, the result may indicate signs associated with the condition.
In a 30-second test, Apple Watch may help identify signs of AFib. If results are inconclusive or symptoms occur intermittently, taking additional readings over time may provide more context.
Are Apple Watch ECG readings accurate?
Since Tim Cook stood on stage and announced the arrival of the ECG app, cardiologists and health experts have studied and evaluated how accurately the watch is at detecting irregular rhythms.
After all, ECG measurements have traditionally been performed using clinical equipment in healthcare settings, making their arrival on a consumer smartwatch a notable development. Apple has also published research related to its heart monitoring features, including the Apple Heart Study conducted in collaboration with researchers at Stanford Medicine.
To obtain clearance from the FDA in the US and then the CE mark for use in the EEA, it must meet a certain standard of accuracy. In the study, during testing of 588 participants in a controlled environment, the ECG app demonstrated 98.3% sensitivity for classifying AFib and 99.6% specificity for classifying sinus rhythm.
The technology isn’t flawless, and the watch can’t definitively confirm that you have AFib. For one, the ECG app also does not continuously monitor heart rhythm. Apple also states that the ECG app is not designed to detect heart attacks, strokes, blood clots, or conditions beyond certain heart rhythm irregularities.
How to set up the ECG app on Apple Watch
To use the ECG app, you’ll need a compatible Apple Watch model, including Apple Watch Series 4 or later, such as Apple Watch Series 10 (excluding Apple Watch SE models), or Apple Watch Ultra models where the feature is available.
You’ll also need compatible versions of iOS and watchOS installed to ensure the Health and ECG apps work correctly and the ECG function is available.
Next, open up the Apple Health app on your phone.
If the ECG function is not already set up, you’ll likely receive a prompt to do so. During setup, you’ll be asked to enter details such as your date of birth before taking your first ECG reading.
How to take an Apple Watch ECG reading
After completing the initial setup, you can take an ECG reading at any time by opening the ECG app on your Apple Watch.
Before you go any further, you want to ensure the watch fits snugly on your wrist—not too tight or too loose—and then, ideally, rest your arm on a table or your lap.
That’s Apple’s recommendation, though in our experience, the watch can often complete a reading as long as you remain reasonably still.
Then, touch your finger from the opposite hand against the Digital Crown. You don’t need to do this too hard—simply rest your finger on the Digital Crown without excessive pressure.
You’ll then see a real-time ECG waveform and a timer counting down from 30 seconds. After 30 seconds, the watch will display your ECG result.
Apple Watch ECG results: What do they mean?
Sinus rhythm: If your heart rhythm appears consistent with sinus rhythm and falls within the ECG app’s supported range (typically 50–100 BPM), you may see a Sinus Rhythm result. Although repeated readings are not necessary, you may still want to turn on the Irregular Rhythm Notifications (more on that later).
Atrial fibrillation: The watch has detected an irregular heartbeat pattern within those same heart rate boundaries. If you get this result, Apple recommends discussing it with a healthcare professional, particularly if you are experiencing symptoms.
Low or high heart rate: The ECG app may return an inconclusive result if your heart rate falls outside supported ranges. There are many 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 regularly notice unexpectedly high or low heart rate readings or experience symptoms, consider discussing them with a healthcare professional.
Inconclusive: This can happen for several reasons, including movement during the recording, poor contact with the watch, or heart rates outside supported ranges.
Set up irregular rhythm notifications on Apple Watch
In addition to manual ECG readings, Apple Watch can also periodically check for signs of irregular heart rhythms in the background, typically when you’re still. This feature works separately from the ECG app and is designed to look for rhythm patterns that may be consistent with atrial fibrillation (AFib).
Background rhythm checks can provide additional heart rhythm information over time alongside manual ECG readings. Follow the steps below to turn on irregular rhythm notifications.
- Open the Health app on your iPhone and head to the Heart section.
- From there, find Irregular Rhythm Notifications and follow the setup process. You may be asked to confirm details such as your date of birth and whether you’ve previously been diagnosed with atrial fibrillation (AFib).
- Once enabled, Apple Watch can periodically check for signs of irregular heart rhythms in the background. If rhythm patterns that may be consistent with AFib are identified across multiple background checks, you may receive a notification.
