Kardia Mobile and Low Heart Rate

Anyone out there using Kardia Mobile with a resting HR under 50? As you know Kardia Mobile needs higher then 50 to test for A-Fib. How are you dealing with this? I try to move around while taking a reading to get the HR up but that at times it gives "unclassified" results. If I sit still while taking a reading, I'll get "Your heart rate is less than 50 beats per minute which is slower than normal for most people. Atrial fibrillation was not detected". With that result I guess I can assume I'm ok with respect to A-Fib.

Anyone other Kardia Mobile users have experience with this too?

It's unlikely you're in afib with a rate under 50, but if you want to make sure, just measure the distance between the R wave peaks (R waves are the tallest peaks). There will be some variation, but not much. Or simpler still, just feel your pulse and see if you can tap your foot in time with it. If you can, it's not afib.

{edit - Carey posted while I was composing this} I've used a Kardia since 2014 and I can have resting HR less than 50, but average afib rates are never that low and usually much higher. I assume you don't have a subscription, which will plot out a heart rate vs time graph for the reading. You can do this yourself, as afib beat to beat heart rates are normally highly variably variable. One way to do this is to count small boxes (5 small boxes to a large box - 1 second - on the chart) between the R peaks on the the waveform. A heart rate of 50 would have 6 small boxes between beats. If you do this for your reading & either plot or just look at the values, you should be able to see the whether it is variably variable, indicating afib. If the values are +/- 5 or so BPM, likely normal. Afib can be +/- 50 BPM, but everyone is different. Mathematically, to convert small boxes to beats per minute: BPM = 60/(number of small boxes/5). So in the case of 6 small boxes: BPM= 60/(6/5) =50.

I'm attaching a 5 minute section of an afib episode heart rate (BPM) vs time graph and then a 1 minute zoom in of the 5 minute graph (1 minute is as small a window as I can use with this software). These were recorded with an ECG quality chest strap with an app developed for research.

Another thing would be to look at the PDF of the ECG and see if the waveforms have a "p" wave. The absence of a p wave can be indicative of afib. However, with the normal right & left finger/thumb on the Kardia (a Lead I presentation), the p wave can be obscured. A Lead II presentation, such as right thumb & left knee can sometimes give a better image of the p wave.



Edited 1 time(s). Last edit at 02/23/2025 05:47PM by GeorgeN.

Thanks, guys, for that info.

Taking a pulse may be the way to go for me. While taking it for 1 minute I think I'll feel 2 or three beats out of rhythm from all the rest, Not sure if its A-fib or not. The majority seem to be in consistent rhythm. This is why I'd like to confirm with Kardia.
As for the numbers and counting boxes on the EKG, I think I understand but the thing about Kardia Mobile is the convivence and speed of not having to do all that. I want to know quickly and move on.

As a side note, I've been dealing with persistent A-fib for 20+years that gets corrected every 9-12 months with cardioversion. My HR has historically been low. I'm fortunate I don't get the high HR kind, and I am asymptomatic. This is why I do KM daily. It's only been recent that the HR has now gone below 50 while resting.

My main question is if KM can't do less than 50 BMP can I at lease feel somewhat confident that the positive bradycardia results along with the phrase "A-fib was not detected" mean I'm in Sinus?

You don't need to feel your pulse longer than 15 seconds. Afib isn't subtle and it's never just a single odd beat here and there. If you're in afib, your pulse will be obviously irregular and it will be like that continuously.

If KM isn't even trying to detect afib with a pulse below 50, I don't think you can interpret "afib not detected" as proof.

One workaround is to get your heart rate above 50 with exercise, then sit down and take your ekg. In any event, the Kardia interpretations are not as accurate as a good electrophysiologist, so you can show any questionable EKG to an ep for analysis at any heart rate.

Jim