Can Apple watch ECG detect possible signs of stroke?

The Apple watch ECG is a step up from the Apple Watch's existing heart rate monitor that it can now measure a user's heart rhythm, and can notify them when it detects patterns in their heart data that appear to be atrial fibrillation, a type of irregular heart rhythm. The watch is also able to send a wearer's heart data to a physician via PDF.

"FDA worked closely with Apple as they developed and tested these apps, which may help many users identify health concerns more quickly. Healthcare products on smart watches may help users seek treatment earlier and will empower patients with more information about their health," FDA Commissioner Scott Gottlieb, MD, tweeted.

The Apple watch ECG function can detect an Atrial Fibrillation or AFib which is a quivering or irregular heartbeat (arrhythmia) that can lead to blood clots, stroke, heart failure and other heart-related complications.

How does it work?

To understand the Apple watch ECG function, we first need to talk about a traditional ECG.  The ECG or electrocardiogram measures the electrical activity of the heart. In order to measure the electrical activity of the heart we need two or more electrodes that have a vector that passes the heart these electrodes give  information to the computer we can calculate the voltage difference and then based on the vector and those voltages we can diagnose various pathologies of the heart.

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The Apple watch is essentially a lead one ECG. The first electrode is the ceramic  back on the actual watch body and the second electrode is the crown, which you touch with your  opposite hand finger. This lead one ECG is very effective at measuring the rhythm of the heart and that's why this is such a good fit for detecting atrial fibrillation It's important to note however that the ECG function only works when you have the your finger touching the crown and you actually ask the Apple watch to do an ECG.

It can actually prompt you as well, so using the optical sensors on the back of the watch and uses PPG (photoplethysmography) to detect your heart rate. This is a technology that we've seen and the other Apple watches and various fitness trackers and other smart watches. If he Apple watch detects an irregular heart rate it will prompt you to perform an ECG.

How can useful is the Apple watch Ecg?

Certain factors may increase your risk of developing atrial fibrillation, such as Age, Heart disease, high blood pressure, other chronic condition, drinking alcohol, obesity and if you have a family history. Sometimes atrial fibrillation can lead to complications such as Stroke.  In atrial fibrillation, the chaotic rhythm may cause blood to pool in your heart's upper chambers (atria) and form clots. If a blood clot forms, it could dislodge from your heart and travel to your brain. There it might block blood flow, causing a stroke.

The risk of a stroke in atrial fibrillation depends on your age (you have a higher risk as you age) and on whether you have high blood pressure, diabetes, a history of heart failure or previous stroke, and other factors. Certain medications, such as blood thinners, can greatly lower your risk of a stroke or the damage to other organs caused by blood clots. [Mayo Clinic: Atrial Fibrillation ]  

This is definitely useful and there's a lot of promise here, but on a population level, we're not sure what this is going to do no test is 100% perfect. A lot of the functionality and the effect of the Apple watch is going to depend on the ECG sensitivity and specificity. No test is 100% perfect, Apple enables the ECG function and we see a lot of people using this and have more data points.

The concern is that patients may put too much emphasis on the data provided by their Apple watch. For example, if a patient is symptomatic and they run an ECG on themselves and it says no Afib is detected, they may have a false sense of security, and maybe without the Apple watch they would have gotten properly worked up and gotten the treatment that they need and with Apple watch they're more likely to say, “oh I'm ok again.” We won't really know until we see the function out in the wild the second issue is essentially after treatment over screening and over treatment a lot of Afib is asymptomatic or you don't necessarily need to work up but if this is detecting a lot of those instances there will be a subset.

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Some lives are definitely going to be saved by the Apple watch, without a doubt; there are also a subset of patients that will be receiving a treatment that is not necessary. It can add to your stress if you don’t know how to read the results and make you paranoid, as your doctors are obligated to check everything to be sure, you may end up getting a treatment that you don’t really need.

But if you have Afibs, heart disease, or high blood pressure, maybe the Apple watch ECG function may actually be handy to monitor your heart and send the data to your doctor for a reading. Apple may have included this feature to monitor the progress of your heart health, but never consider it as your cardiologist.

While you are here, you may be interested with The "IF's" why the Apple watch is not for you