Afib and Apple Watch - Correlation between Afib detection algorithm and HRV

[AAAA223344]

Hi, do you know how long do you need to be in Afib for Apple Watch to detect it? I had two recent episodes where the algorithm didn’t pick anything up, However, according to the watch, during my sleep I was for 30/45 minutes with HRV above 200 ms… which doesn’t look good… but I didn’t feel anything and didn’t wake up… Has anyone done any research on this? Thanks!

[BobD Volunteer]

As far as I am aware, Heart Rate Variablity is not a measure or indication of AF which is easily seen by lack of a P wave on the ECG.

[AAAA223344 in reply to BobD]

👍Thanks for your reply

[kitenski in reply to BobD]

It's definitely an indicator of "something" (could be ectopics, PACs etc) on the Apple Watch especially when it's so high. Speaking from personal experience as an AW user and Afib, big thread about it here healthunlocked.com/afassoci...

[mjames1]

A number of variables have to be met before the Apple Watch will notify you that in you are in afib. I have documented a fib via EKG many times and often the Apple Watch misses it.

Indeed your HRV of 200 may have been afib, as I'm assuming it's significantly lower normally. Also, if you have the sleep function activated, it will tell you your heart rate during sleep, which may be another indirect clue that you were in afib.

Of course if you happen to catch the episode with the Apple watches, EKG function that would be conclusive.

Jim

[AAAA223344 in reply to mjames1]

Many thanks for your reply. Really appreciated.

[Ennasti]

I’ve not had any AF that I’m aware of for at least 12 months. My HRV regularly spikes upwards up to about 250. I believe it is when I’m suffering arrythmia clusters (my personal term). So when I have sinus arrhythmia, a heap of PVCs and PACs and especially when my left bundle branch is playing up. It can happen at night or during the day.

This was a few days ago at night. I mostly sit down around 15-30 but have regular spikes like this.

HRV graph

[AAAA223344 in reply to Ennasti]

Many thanks for your reply 👍

[Jonathan_C]

The apple watch (and other watches that measure your HR on wrist) measure your pulse.

A-fib is an electrical thing - to accurately detect a-fib you need to measure the electrics in your heart. That is why they put 18 different patches on you when you have an ECG.

[Poochmom in reply to Jonathan_C]

My apple watch determined my AFib but you have to use the ecg function which requires that you put your finger on the dial while using the ecg app. I never had a problem with it picking up my AFib and my ep accepted the reading as accurate.

[OzJames]

I get the odd ectopics and I believe that’s what my Apple picks up when HRV can hit 100-400 for a minute or so. The watch does constant checks via its algorithm when it picks up AF it continues to check and I think if it picks up 3 in a time frame you get a notification. My notification often says possible AF at 1.02pm, 1.20 and 1.40. In other words one episode of AF at say 1.02 and no further detected after that then you will not get a notification

[AAAA223344 in reply to OzJames]

Many thanks Ozjames, that makes sense, I have checked, and when when Apple Watch detects high HRV starts checking every 15-20 minutes… when I got the AF alert, I always had 5 of them (so more than 1 hour)… in the high HRV with no AF alerts I had only 3 or 4… so it could have been a short AF episode, but not long enough to trigger the AF alert…

[OzJames in reply to AAAA223344]

I forgot to mention I’m 66 and have had AF on and off due to triggers mentioned since 35. I was lucky only once every 4 or 5 years till 2022. So maybe only 7 or 8 episodes in 31 years. I attribute to healthy lifestyle eating well and exercise every day. The medication route started at 66 when my body maybe couldn’t adapt as quickly. Stay positive you never know you could be a lucky one

[babs1234]

have got the setting in history? Which only tell you once a week what % of AF you were in that week.

[Ppiman]

I think the Apple Watch looks only for the kind of heart beat irregularity that is typical of AF and only checks this intermittently, thus missing "micro-AF". Also, the heart rate monitor is also more easily affected by physical factors and might not measure heart rate always very accurately. The ECG function is very different and far more accurate.

Steve

[Thomas45]

You did not feel anything. AF in itself won't kill you. Go to bed and sleep. If I were you, I'd take your apple watch off, put it in a drawer and forget about it. As for your AF, respect it. When, like me you have permanent, though asymptomatic, AF, respect it and live with it.

[AAAA223344 in reply to Thomas45]

Many thanks Thomas, I really appreciate that answer… my GP also said that, but then the cardiologist said that I don’t need any medication / procedure yet… however, if the episodes start getting more frequent I should start considering it…. How can I tell if they are getting more frequent if I don’t wear the watch at night??? But yeah, completely agree with your comment… I’m in my late 40s, and after nearly a year since the first Apple Watch alert, the anxiety created by sleeping with the watch, checking all the metrics and lack of proper sleep has impacted much more my life than the AF itself… not to mention that some of the AF episodes could have been triggered but this same anxiety / stress… Thanks 👍

[Thomas45 in reply to AAAA223344]

I am 79.

[Buzby62]

The watch cannot conclusively show AF without doing the ECG electrically. What it does is alert to signs of irregular heart rate (HRV is excessively high) which could be AF, then you do the ECG to check and confirm. In my experience it can take 5 hours or more to alert and sometimes not at all but like you I can see episodes of high HRV which I am pretty sure were AF episodes that the watch did not alert to.

Also the instantaneous heart rate reading is meaningless when in AF and best ignored. The average HR on the ECG is good though.

I have learned to ignore everything except the ECG while having an AF episode.

Apple links for info

support.apple.com/en-us/120277

support.apple.com/en-us/120276

Best wishes

[AAAA223344]

Many thanks for all your comments, it’s great to have this community, really appreciated. 👍😀

Yes, it looks it’s about duration.. when Apple Watch detects high HRV starts checking every 15-20 minutes (instead of the usual 2 hours)… when I got the AF alert, I always had 5 samples of them (so more than 1 hour)… in the high HRV with no AF alerts I had only 3 or 4 (45 minutes max)… you are right ECG is best, but in my case it usually happens during my sleep..

So two options, to activate AF history (then Apple Watch checks every 15-20 minutes when at rest, but it only shows if above 2% per week (3Hours 22 minutes), which wouldn’t work for me) or AF alerts (checking approx every 2 hours, but you need more than one hour to trigger the alert, so it could be easily missed)…

[Buzby62 in reply to AAAA223344]

Neither mode, AF Alerts or AF History will capture all your AF, or to put another way both can miss episodes. Apple say this on their support pages. It’s definitely not a substitute for a Holter monitor which catches everything. I find it really useful but you need to understand there will be some anomalies or it can cause more anxiety which can trigger more AF.

Another link for AF History mode support.apple.com/en-gb/HT2...

Best wishes

[Buffafly]

I think you should ask your cardiologist to explain more clearly what his criteria are. In the meantime I would take your watch off at night and don’t check or measure anything unless you have AF that you are aware of for more than ten minutes. If you can’t manage that lock the Watch away and give the key to a friend to look after.

[Halfheart]

The Apple Watch algorithms are complicated. If you tell Apple Health you have been diagnosed with afib, then it does not alert you for afib anymore, instead it just gathers stats on how much afib you are having and tells you every Monday what percentage of time you were in afib the previous week. It does keep measuring HRV, once every 15 minutes if you are on the latest watch software.

If your HRV goes above 150 - 200mS its extremely likely (100% correct for me so far) that you are in afib, but its not good enough for a diagnosis, so they can't use it for that. On your iPhone you can use the Health app to give you a chart of your HRV over any time period you like, and it's usually an accurate chart of all your afib episodes. They all show up as spikes in HRV.

[JezzaJezza]

Hi there are 2 ways to detect AF with the Apple Watch.

1. You capture an ecg with your finger on the crown of the watch and then the algorithms determines if it detects AF

2. If you have been diagnosed with AF there is another setting in Apple Health where the watch monitors in the background your AF level. This is reported to you every Monday at 8am and allows you to track over time. It never actually says 0%, for regulatory reasons it says ‘2% or less’ but if it is more it will say (example) ‘4% of the time’.

Another good way to check your ecg results is with the app Qaly. It is subscription at 4.99 per month but takes your ecg reading and gives a full report on the PQRST readings and can detect in excess of 20 different arrhythmia such as (example) AF, PAC, PVC, SVT, bigeminy etc.

[kitenski in reply to JezzaJezza]

there is a third method where it will flag it if detects episodes automatically, only when option 2 is switched off. JezzaJezza

[Gumbie_Cat]

I now have permanent AFib, so that my HRV always shows as around 200, so I just ignore it these days. When it was still paroxysmal, it was indeed an indicator of each bout of A Fib. It went straight back to a normal level when I converted back to sinus rhythm.