AF Association

Fitbit better than a hospital HRM - yes really!

I am in permanent AF - a largely asymptomatic condition for me. Recently I went into an emergency department in Australia on a non-AF related issue. While there I was hooked up to the hospital heart rate monitor, the type they clip to your finger. It recorded a very high heart-rate, then plunged suddenly and set off the alarm at intervals as its programming tried to figure out what was happenning. Eventually the nurse took my pulse the old-fashioned way using her fingers, and the value was pretty close to what the Fitbit Charge HR on my wrist said. She was quite an experienced nurse and said that the monitor had trouble with AF patients.

I was used to taking my heart-rate long before I had AF using the old heart rate monitor chest strap, which was useful when I entered my AF, but did over-record during exercise. My Fitbit seems pretty accurate at rest but, as with many non-AF users, it records a slightly too low value when exercising.

The reason the Fitbit (and maybe other wrist wearable devices) work for AF users seems to rely on its programming which has a distinct lag in recording trends in the rate. So while a super accurate device reads a couple of seconds of beats together as a sudden rise in heart-rate, the Fitbit ignores it assuming that the less reliable method it uses (of a pulsed light) has made an error, and averages out over a much longer period.

So in a way the same thing that makes these wrist wearable devices less suitable for non-AF athletes actually makes it more suitable for those experiencing AF.

9 Replies

Interesting - will look into that. Thanks for posting.


Don't know much about Fitbit are there different types if so which one do you use.


There are many different types - though not all measure heart rate. I use a Charge HR (replaced recently by a Charge 2), but have just bought a Blaze. Other companies who make wrist wearable HR trackers largely use the same technology as well, though each has its own particular features.


Thank you I can have a look at some now.


I love my Fitbit HR Charge. Works well as a light weight watch also.


A little warning.

Just over a year ago I had a severe attack of AF and had to fight to keep conscious, was sweating and felt sick. I'd taken my pulse manually and all appeared ok. An ambulance was called and on paramedics checking my pulse manually it still appeared ok. However, they discovered my heart was indeed racing but was going too fast to register in my wrist. This is what put me off buying anything that recorded from the wrist.

I bought a stethoscope instead.


1 like

Really interested to read this thread. I had a Fitbit Charge 2 for Christmas and am still evaluating it.


The chest strap shows your real heart rate. The fititbit underestimates your heart rate if you have afib, because the fitbit measures the pulse rate. In normal case the heart rate and the pulse rate value is equal, but during arrhythmias pulse rate is usually lower. The difference is called pulse deficit and it has diagnostic value. Means that although the heart is contracting, but some contractions not pumps blood. If you let say biking and you have both fitbit and chest strap when you experience that the two rate is different it means that you got arrhythmia.


Fitbit picks up the pulse in the radial artery(wrist). If the a fib is too crazy, the pulse wont be detected. When I go into a fib my fitbit goes blank. I like my fitbit as its reassuring to see my pulse and know its ok. On the rare occaisions Im in a fib, I dont need a fitbit to tell me that, the giant fish flopping in my chest lets me know, lol


You may also like...