How Apple Watches Detect AFib? Key Difference!

Apple Uses Two Distinct Ways

To put it simply Apple Watches depending on which kind of series you are using deploys two different methods to measure the AFib:

• Using greenlight aka PPG method.
• ECG monitoring (this one is not available in earlier models).

For those who are aware of working of these two methods, you don’t need to read this bit, but if you don’t then here is little more context for you: Both PPG method and ECG method works in parallel to detect your heart rate. However, since ECG method is not widely available (You must have Apple Watch Series 4 or later) and you require the application for it as well your smartwatches’ go to method of BPM monitoring is always PPG. This right here is both reliable and in many cases quite accurate too. Of course, in battle of precision ECG holds an upper hand, in context of AFib detection both of them can be sufficient – to an extent.

But What Is AFib In First Place?

Atrial fibrillation (AFib) is a form of irregular heart rhythm characterized by the upper chambers of the heart beating out of synchronization with the lower chambers.

As per the CDC, approximately 2% of individuals under the age of 65 and 9% of those aged 65 and above are affected by AFib. The prevalence of irregular heart rhythm tends to increase with age. Some individuals with AFib may be asymptomatic, while others may experience symptoms such as a rapid heartbeat, palpitations, fatigue, or shortness of breath.

If you are still having hard time understanding it you can follow this analogy:

Imagine your heart is like a clock that goes tick-tock, tick-tock. Sometimes, in a condition called Atrial Fibrillation (let’s call it AFib for short), the upper part of the heart doesn’t follow the tick-tock rhythm properly. It’s like the top part of the clock is doing its own dance, not matching the bottom part.

Now, some people, especially older ones, may have this happening. Some feel normal, but others might feel their heart beating really fast or get tired quickly. It’s like when you play a game and your energy goes down.

The good news is, people with AFib can still be healthy and play and do all the fun things. They can exercise, eat healthy food, and go to the doctor to make sure everything is okay. The doctor might check how much of this special dance is happening in the heart.

AFib Tracking By Apple…

Since there are two ways in which Apple Watches detect AFib, it would be appropriate to learn the difference between the two to understand what is actually happening:

PPG Tracking For AFib

Consider your Apple Watch is like a little health detective on your wrist. It has special sensors and lights that can check your heart by measuring the blood in your wrist. This helps the watch know how fast your heart is beating and even if there’s any irregular rhythm, like a special dance your heart might be doing.

The watch doesn’t watch your heart all the time because that would use a lot of energy. Instead, it checks every two to four hours by making a kind of chart called a tachogram, which shows the time between heartbeats. If you decide to turn on a special feature, the watch can also look for signs of an irregular heart rhythm, like when your heart might not be dancing the usual way.

If the Apple Watch thinks something might be wrong with your heart rhythm, it starts checking more often, like a detective looking for clues. But it only does this when you’re not moving too much, so it can get a good reading. If, in two days, it sees five out of six times that your heart is dancing irregularly, it sends you a message to let you know. You can also see more details about it in the Health app on your iPhone.

But here’s the cool part: if it sees two times in a row that your heart is not dancing irregularly, it goes back to checking every two hours. It’s like the detective taking a break and saying, “Okay, everything seems fine now!” So, the smartwatch is like your little heart guardian, keeping an eye out for anything unusual and letting you know if there’s something to pay attention to.

ECG Tracking For AFib

Now imagine your Apple Watch as a smart gadget that can check your heart in a really special way. It has a cool feature called the ECG app, and it uses some special parts to do this.

Firstly, there’s a tiny metal part in the Digital Crown (that’s the little button on the side of the watch) and a super thin layer on the back of the watch. These work together to create a circuit, kind of like a loop.

When you want to use the ECG app, you open it on your Apple Watch and put your finger on the Digital Crown for 30 seconds. At the same time, the back of the watch is checking your wrist. This creates a little loop that helps the watch read the electrical signals controlling your heart.

After that, the watch does some smart thinking with its special computer brain (algorithm) and decides if your heart is in a regular rhythm (they call it SR), if there’s a type of irregular rhythm called AFib, or if it’s not sure (inconclusive).

If you have a newer version of the ECG app (they call it ECG 2.0), it can do even more. It can tell if your heart is irregular and beating fast, and it can also figure out if the recording wasn’t very clear.

All this information, like how fast your heart is going and if you felt any weird symptoms, gets stored in the Health app on your iPhone. You can even turn it into a PDF and show it to your doctor if you want. So, the ECG app is like a super-smart heart checker on your wrist that can help you keep an eye on your heart health!

How You Can Set Up It On Your iPhone

In order to set up your Apple Watch for AFib tracking you must have your iPhone and Apple Watch synced. After that you must make sure that your smartwatch as well as smartphone is both updated to the latest available OS version. Heart Rate and Wrist Detection must also be turned on but that is like secondary priority. In any event check for all of these things before you head to your iPhone to follow these steps:

• On your iPhone, open the Health app.
• Tap Browse, then tap Heart.
• Tap AFib History.
• Tap Set Up, then tap Get Started.
• Enter your Date of Birth.
• Select Yes to indicate that you have been diagnosed with AFib by a doctor, then tap Continue.
• Tap Continue to learn more about AFib History, the results you may see, and life factors.
• Tap Done.

It should be noted that for accurate and precise AFib monitoring you must have your Apple Watch on your wrist on you for prolong period of times. According to Apple the minimum requirement is 12 hours a day for 5 days a week.

Is Apple AFib Tracking Accurate?

In December of 2020 Apple published a document stating different aspects of AFib tracking using Apple Watches. One such factor was also focused on the accuracy of these little devices. According the document Apple’s AFib tracking features, including the Irregular Rhythm Notification Feature and the ECG app have shown promising accuracy in detecting irregular heart rhythms, particularly atrial fibrillation (AFib).

For the Irregular Rhythm Notification Feature, the Apple Heart Study demonstrated a high concordance with AFib identified by an ECG patch, suggesting that the notification was accurate in representing the presence of AFib in the majority of cases. However, it’s mentioned that in some instances, a notification might indicate the presence of a different type of arrhythmia.

Regarding the ECG app on the mentioned Apple Watch series, the passage states that the electrical heart sensor, along with the ECG app and algorithm, demonstrated a high sensitivity of more than 98 percent and specificity of more than 99 percent in identifying AFib. This means that, in the study, the Apple Watch’s ECG feature was very good at correctly identifying the presence of AFib and distinguishing it from other heart rhythms.

For your ease we have added the link of published document below. You can check it out yourself. Moreover it’s our advice that while these results suggest a high level of accuracy, any health-related technology, including Apple’s, should be used as a tool to complement professional medical advice and not as a definitive diagnosis.

Important Things To Keep In Mind

If you are already using the AFib tracking in your Apple Watches here is what you should know: turning on the power saving mode can disable the heart rate tracking in background which could lead to disjointed results. Another thing to keep in mind is your Apple Watch will never be able to forecast or predict event like heart attack or stroke. These devices despite what they can achieve are neither reliable nor accurate enough to reach those conclusions.

Users are always advised to be aware of the educational information provided by Apple and the limitations of the algorithms, as mentioned in the passage. Additionally, individual experiences may vary, and any concerns about heart health should be discussed with a healthcare professional.