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  1. #1
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    Heart rate monitor with atrial fib

    I have had an irregular heartbeat (atrial fibrillation) for many years. My cardiologist does not put any restrictions on physical activity and I like to ride. When I use the stationary bicycle at the gym it has a heart rate monitor built in, but it cannot seem to accurately monitor my heart rate - the display goes blank after a while.

    I wanted to buy a heart rate monitor to wear when I am out riding. But I am concerned that it will not be able to properly monitor and display my heart rate due to the atrial fibrillation (a-fib).

    Is there anyone here who uses a HR monitor when they ride that is also has a-fib? If yes, what brand and model works for you?

  2. #2
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    The ones at the gym get beat up pretty good. Was it the type that measures it via touch or a chest strap?

    If you know someone that rides with one ask them if they would loan it to you for ride. That was how I was first introduced to them years ago. Short of someone responding here that may be the best test.

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    Yes it was the type that measures by touch.

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    I think the answer is "maybe" and the only way to find out is try some of the better heart rate monitors (Polar is one of them).

    The electrical signal from your atrial fibrillation is generally smaller than the one from your two ventricles (responsible for most of the heart's pumping) because the muscle mass of the two atria is much less than that of the two ventricles. The magnitude of the electrical signal from the ventricles contracting, called the QRS complex, varies depending upon where the electrodes measuring it are located. This is one reason they use twelve leads for a standard electrocadiogram. Heart rate monitors only use two electrodes. You should try wearing the heart monitor's electrode strap in different locations to see if you find a location with satisfactory readings.

    This seems to be the experience of users with atrial fibrillation. At this LINK they state:
    However, there are a very small number of cases in cardiac rehabilitation
    where the heart rate monitor will not work, for example: low voltage R-wave
    signals, atrial fibrillation or bundle branch blocks. In your case we would
    recommend to check the operation of heart rate monitor during ECG
    measurement at rest and during exercise. Polar has developed the
    transmitters to detect a normal ECG and the issues you described (on
    earlier UK records) may have have an effect on your ECG. Thus, cause the
    transmitter not to detect the heart rate.

    Should it be that the transmitter cannot detect the heart rate being in the
    "normal" position (on the chest), where the signal is normally the
    greatest, it could be possible that signal of your heart is greater
    somewhere else. Could you try to move it around e.g. wear it on your back,
    on your stomache, on your sides?

    Thus as another poster suggests, if possible borrow one or more models, try wearing them in different positions, and see if you get satisfactory results. I suspect the better, more expensive models may have low and high pass frequency filters and perhaps even auto gain adjustment that may let them detect the larger QRS signal and ignore the smaller fibrillation signals.

    Do let us know how this works out for you. Best of luck.

  5. #5
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    Quote Originally Posted by ARider2 View Post
    Yes it was the type that measures by touch.
    I've often found those gym-based handle HRM's to be quite useless, for exactly the reasons you cite. I don't have a-fib, but never have any issues with my Garmin chest-strap. If your concern is just because of the exercise bike experience, then I wouldn't worry too much about that translating to a chest-strap based system.

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    Thanks everyone. I will just have to try out a couple of them to see what works.

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    My experience is that HRMs don't give good readings with A-Fib. It gives you some idea of the general level of effort, but you will see lots of numbers going up and going down as the unit tries to make sense of your heartbeat.

    I tried several models, including some rather expensive Polars, and nothing worked.

    Fortunately for me, I've been successfully converted to sinus rhythym, so I don't have this issue any longer. (and like you my cardiologist encouraged exercise, even with a-fib)

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    Senior Member SouthernGirl's Avatar
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    Another thing to consider, even though the rate changes rapidly and seems that the monitor is not picking up, it is possible that it's accurate. I am not talking about the touch ones. I don't trust those for anyone. The ones that you strap on around your chest though I trust much more. If the A-fib is uncontrolled, it's an elevated rate. Many people with a-fib flip in and out between sinus rhythm and fib many times during the course of a day. So, that can actually account for the fluctuation in readings.

    The monitor should be picking up on the ventricular contractions (I believe another poster mentioned this). The a-fib normally shouldn't be too much of an interference in and of itself. Now, yet again as another poster said, if you have low voltage QRS complexes it may make it difficult to pick up and then you'd be back to square one with the unreliability.

    The up and down, up and down, may in fact be accurate if you're flipping in and out is basically what I'm driving at in a round about way!

    Hope that was somewhat clear(ish)?

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    According to my cardiologist I do not go in and out of a-fib. I was cardio-verted twice, but each time I returned to a-fib. And this was many years ago. Now I am just in a-fib.

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    I also have a irregular heart beat and use an old Polar wrist model mounted on my handlebars but it needing a new battery which has to be replace by Polar.

    So have been looking at upgrading to single computer unit.

    I need to see my heart beats like the little heart symbol that flashes on my Polar. Looked a Cateye and it does not flash.

    So Polar has a c100 that if I read the manual correctly, the outside of the symbol does show the actual heart beat.

    Can anyone confirm this?

    Bob

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    Quote Originally Posted by bobzam View Post
    I also have a irregular heart beat and use an old Polar wrist model mounted on my handlebars but it needing a new battery which has to be replace by Polar.

    So have been looking at upgrading to single computer unit.

    I need to see my heart beats like the little heart symbol that flashes on my Polar. Looked a Cateye and it does not flash.

    So Polar has a c100 that if I read the manual correctly, the outside of the symbol does show the actual heart beat.

    Can anyone confirm this?

    Bob
    All of the Polar models work the same basic way. There is a simple EKG detection circuit in the transmitter that sends a "pulse" at 5 Khz each time it detects a heart beat. The watch unit (or the treadmill, etc) counts the pulses that arrive. All of the smarts on in the receiver, not the transmitter.

    There's a good diagram of this in this patent: http://www.freepatentsonline.com/5632279.pdf (which describes the "coding" process that Polar uses)

    Each time there is a pulse, the heart symbol will light up. In some Polar models, not all of the pulses are counted when they arrive at irregular intervals: this is intended to make the display more accurate in a noisy environment, and it also makes the device slightly more accurate for people with some arrhythmias.

    Even so, you will still see a flash of the little heart symbol every time the sensor detects a heartbeat, even if that pulse is not counted in your heart rate display.

    My experience was that this wasn't very effective: the heart rate numbers still went up and down irregularly. It was possible to get some sense of when I was working hard and when I wasn't, but doing any sort of "zone" training was out of the question.

    Since all Polar transmitters use the same circuit (except that some of them code the pulse with an amplitude modulated signal), I would not expect that any of the Polar models to be any better or worse at counting your heartbeat. I tried a simple one and a fairly expensive one, and the results were very similar.

  12. #12
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    I have had a lot of patients ask about this. The problem with HR monitors and A-Fib is that your rate is constantly changing, so the monitor is only going to show you trends up or down over time, as the rate is not going to ever stay the same. You may be lucky and have a ventricular response rate that is reasonably "tight," meaning it only ranges 10-20 beats per minute difference in conduction time on average, but, you won't know until you try. If your baseline ventricular rate jumps around from the 50's to the 90's, the monitor is going to be jumping all over the place. In the hospital, we run a strip on an A-Fib patient and give a HR range, not a definite rate.

    A strap monitor will work better than the hand-holders at the gym, but whether it will work well enough for you to use and not go insane depends. The bottom line is that you have an irregularly irregular heart-rate. Digoxin (or other medications) may control the ventricular response, but, unless you are in a 2:1 flutter or something, you will always have a number that jumps all over the place on a monitor that is working perfectly.

    Good luck.
    "It turns out that what you have is less important than what you do with it."

  13. #13
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    Quote Originally Posted by goalieMN View Post
    I have had a lot of patients ask about this. The problem with HR monitors and A-Fib is that your rate is constantly changing, so the monitor is only going to show you trends up or down over time, as the rate is not going to ever stay the same. You may be lucky and have a ventricular response rate that is reasonably "tight," meaning it only ranges 10-20 beats per minute difference in conduction time on average, but, you won't know until you try. If your baseline ventricular rate jumps around from the 50's to the 90's, the monitor is going to be jumping all over the place. In the hospital, we run a strip on an A-Fib patient and give a HR range, not a definite rate.

    A strap monitor will work better than the hand-holders at the gym, but whether it will work well enough for you to use and not go insane depends. The bottom line is that you have an irregularly irregular heart-rate. Digoxin (or other medications) may control the ventricular response, but, unless you are in a 2:1 flutter or something, you will always have a number that jumps all over the place on a monitor that is working perfectly.

    Good luck.
    Thanks, I have used this new Polar a few times and its better than my old one as when I am on river along power lines it reads OK. I am 77 so do take it easy. I use to make a long run with by rate around 120 but now I ride a bit slower and stay around 110. Couple of times over the years I ran high rate up to 180 and did not feel well. I stopped and walked around and heart rate returned to normal after a while. So my doc sent me for a stress treadmill and passed it fine. Also before some back surgery last spring I had an extensive treadmill and machine taking pictures of my heart and that was OK. I do have had an arthrima for years so I am careful. Probably the monitor when biking is more of a security blanket, false or not!

    My normal ride is 4.5 down to beach on street traffic. Then on river bike way I go 6 miles but now I stop half way and have a few sips of gatorade and water. Then I have slow ride through the park and home for 16.5 miles total over 2 hours.

    Bob

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    I took a ride today with my new Sigma BC1909 HR computer. It has a chest strap and it was able to measure my heart rate to some degree. The HR monitor seems to reflect my heart rate, but at a delayed pace. It does not seem to be entirely accurate or very responsive, but it does give me a general trend as far as my heart rate. For example, the number displayed on the HR monitor would trend upward as I exerted myself going up a hill, then it would trend downward as I went downhill. So, I have found a HR monitor that works to some extent. It may not be entirely accurate, but it does give me some idea of what is going on with my HR. I suppose the HR monitor cannot be more responsive or accurate due to my atrial fib.
    Last edited by ARider2; 10-01-10 at 07:55 AM.

  15. #15
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    your heart rate won't immediately track your exertion level, some delay is normal and this is why heart rate isn't the best indicator for doing interval training.

  16. #16
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    I just had an episode of afib and was shocked back to normal. I'm still waiting to see a cardiologist. Meanwhile, I strapped on my heart rate monitor and the numbers are going up and down--not bad, but at a variance that I've never had before. However, my pulse feels normal! Help here if you can: is the electrical signal in my heart varying, but my pulse is still steady? Or what. I'm a bit freaked out. p.s. I just ran out to get a new monitor and then checked my readings on yet another brand while in the store; all give an up/down reading.

  17. #17
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    The problem is, as said in other replies, stems from always trying to measure & update heart rate display every beat. All the programs would have to do is switch to an average calc every 10-15 seconds, like the nurse would do, & we'd have a wonderfully smooth display, even with AFIB. But I've talked to Polar Engineer & he just says their system doesn't work for AFib patients.

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