Apple watch electrodes

[Physalis]

A few days ago there was, in one of the discussions, the assumption that the Apple watch worked on light and the Kardia on electrodes.

However, I have just found this. We live and learn.

"That's where the EKG comes in. An EKG uses electrodes to measure the electrical activity of the heart. A hospital-grade EKG generally consists of 10 electrodes placed on different parts of your body. The Apple Watch Series 4 has two: one electrode on the back crystal and one electrode on the digital crown."

[BobD Volunteer]

I thought UK ECG used 12 leads. All mine have.

[Physalis in reply to BobD]

Yes, but the point's the same. With the Kardia you have two electrodes and you place one finger on each. With the Apple watch one electrode is on the back of the watch on the left wrist, say, and the right finger is placed on the winding mechanism on the side.

[CDreamer in reply to BobD]

I just had one last week for PM check & they only used 4 of the leads. I think it is what they are checking for because normally, for cardiology, I have always also had 12 leads.

[CDreamer]

The iWatch uses green light for measuring heart rate & if you have v6 O2, as do many of the smart watch apps which use in built cameras and green light.

This article explains very clearly how both iWatch pulse meter, ECG and the Kardia band work and the difference between these mobile devices, their uses and an ECG.

The video in the middle of the article is especially helpful at assessing the limitations of the iWatch compared to 10/12 lead ECG.

The Kardia has 2 versions - one which gives a trace = Lead 1 on a full ECG and the Kardia6 which has 3 electrodes and gives a trace = leads 1-6.

cnet.com/health/apple-watch...

[Physalis in reply to CDreamer]

Yes, we are both right. The green light monitors heart rate continually. However, when you do an ECG it uses electrodes.

[CDreamer in reply to Physalis]

As explained in the article.

[Physalis in reply to CDreamer]

I'll read it properly later. I've had my watch for a couple of years now but I had no idea that was how it worked

[momist in reply to Physalis]

And, you can trust the electrodes to graph what your heart is really doing. The green light/photocell approach can't reveal everything going on, but at least the Apple watch doesn't limit itself to a narrow range of rate, and can recognise arrhythmia. Sports watches (e.g. Fitbit) don't in my experience

[Physalis in reply to momist]

I could trust the Apple watch to do an ECG which I could look at when I was in AFib with the rate going up and down over that 30 seconds. That's all I needed. I did an ECG every four hours and put the average rate on to a spreadsheet on my computer.

After I had stopped doing that I realised that I could just have looked at the previous day's heart rate readings and scrolled down and entered the heart rate at 2, 6 and 10 am, 2, 6 and 10pm. I thought they would have been the same.

However, with the ECGs using the electrodes and the hr readings using the green light method, maybe they would have been slightly different.