Atrial fibrillation and Kardia

[Spj57]

I was wondering if anyone else had wide discrepancies in their hr reading between Kardia and their smart watch? My Garmin is usually reading the same as my blood pressure monitor but when I am in AFib the reading from the Kardia is often much higher than my watch. I am wondering which would be more accurate?

[Czech_Mate]

Would it be that it's difficult to measure a heartbeat when it's irregular?

[Eddybear in reply to Czech_Mate]

Personally I would trust any reading from my Kardia Mobile above that of an Apple watch, the former is widely acknowledged by cardiologists as being the most accurate, the latter being more for convenience at a glance.

[Henry20]

When you measure your pulse rate the answer is given as beats per minute (bpm). It is calculated by measuring the number of beats for a certain number of seconds.

Let's say in 10 secs, 6 beats are counted and this becomes 60 bpm. If the measurement time is 20 secs, it might count 21 beats, then your heart rate is 63 bpm. This is a small error and is inevitable as the counting of the beats is asynchronous with your actual beating heart.

This measurement time is unknown for both devices. So some difference is inevitable. If the afib lasts for 10 seconds, say at 120bpm, allof the beats might be captured in the 20 sec measurement but the rest of the measurement time will be made up of a normal heart rate. So you will get an average between the two rates (10 secs @ 120bpm = 20 beats; 10 secs @ 60bpm =6 beats; total beats =26; therefore heart rate =26x3 = 78 bpm)

Depending on how the afib burst and the measurement overlap, you can get very different answers. So both might be right BUT with the Kardia you can see the trace and calculate the bpm during the afib burst for yourself, as you can ensure that only afib beats are in the measurement.

I hope this helps

Henry

[Spj57 in reply to Henry20]

Thank you, that's very helpful.

[fishonabike]

Henry has explained how the difference between readings can happen and I hope that helps, but you might also need to ask yourself why you need an accurate reading?

in most cases it's the overall patterns which are important rather than the actual numbers - for example how much faster your heart rate is in reaction to exercise, how quickly it recovers, how often you have irregular beats, how long the irregular beats persist etc

very few commercially available devices record everything to the accuracy which might be used by a medical device used in a clinical situation, for monitoring and/or diagnosis - so what is it you want from your device? and have you got the right device for doing what you want?

[Spj57 in reply to fishonabike]

Thank you, it was really just I was wondering why during AFib my watch might read 80 but the Kardia 120, although the Kardia reading can jump about during the 30 second reading. I'm not sure how I could track how often I have irregular heartbeats.

[Henry20]

An additional comment if I may:

I have wondered about the way we characterise the heart with basically just the beat per minute; it's easy to measure and does give information.

However, when we are at rest and our heart rate should be constant, for many here that is the last thing we have - a constant heart rate. We could now measure and record the time between heart beats and build up a histogram. I know that when I get ectopics (which is quite a lot of the time) I can feel the difference in time between beats but I cannot measure it.

I just wonder if a histogram could be used used a diagnostic tool. Does anyone know if there is any reported investigation in this area? Or perhaps, it's just wishful thinking.