Rollercoaster

George Newton, the man who contributed  much of the material regarding the interpreting heart rate recording during atrial fibrillation (AF) on the afibbers website [1], had left an interesting comment on my previous post on 27th June questioning whether my Polar RS800cx was a boon or curse.  As illustrated in my post on 28th February, some of my chaotic recordings had raised the spectre of AF, but due to various inconsistencies in the data, I was left in a quandary.  George’s initial conclusion was ‘Your data clearly looks like afib’. 

AF is widely regarded as enigmatic and unpredictable, but in his own experience, George had found that systematic monitoring  using various different methods ranging for simple manual recording of the pulse to recording the full ECG, can provide a large measure of control over the condition  He has virtually eliminated his own AF by adjusting intake of electrolytes and other supplements according to the frequency of premature contractions, which at least in his case, are a fairly reliable indicator of imminent AF.  

Although he has acquired experience of many different recording devices, he largely uses a Polar S810 (similar to my RS800cx) to record the rhythm abnormalities.  By comparison with full ECG recordings, he has established the R-R tachogram signatures of the various relevant abnormalities, including premature atrial contractions (PACs), premature ventricular contractions (PVCs) and AF itself. He has also assembled a body of useful information about the artifacts that can arise from poor electrode contact or movement

I myself have had several reasons for continuing to doubt whether or not I truly had AF. The most important piece of evidence had emerged during a recent relaxed run in delightful countryside in Leicestershire with my friend Marie (who had run in the London marathon with her husband a few weeks after she had been diagnosed with cancer, and has subsequently recovered well from surgery).  During our run through the Leicestershire country-side I was feeling quite relaxed, but when I glanced at my Polar monitor I noted that it was displaying a heart rate around 125 whereas I would have expected a rate of around 110 at that pace.  I immediately stopped to palpate my pulse.  It was regular apart from the decreasing  rate expected on cessation of running.  There was certainly so evidence of AF, so we continued on our way. 

When I got home I was dismayed when I examined the beat-by-beat record of my hear rate (the R-R tachogram).  It indicated a horrible chaotic rhythm throughout much of the run – though frustratingly, it had failed to record the data for about half of the duration of the run,  including the time when I had stopped to examine my pulse manually.  The only absolutely certain conclusion was that my Polar RS800Cx was not storing data properly.  It was impossible to determine if my heart was also malfunctioning.  Nonetheless, the normal manual assessment during a run in which the recorded segments of the tachogram showed a chaotic rhythm raised serious doubts in my mind about the reliability of the evidence for AF.

I had also been puzzled by two other features of my chaotic tachograms.  In the recording I had posted in February, careful inspection reveals that interspersed with the chaos are many brief periods (typically 5-15 seconds in duration) of what appears to be fairly normal sinus rhythm (figure 1).  In fact the heart rate is a little higher than expected for the pace.  Within the periods of apparently normal sinus rhythm, the average rate was 122 bpm compared with an expected rate around 115, but in the icy conditions on that December day, I would not have been surprised if my average heart rate was a little higher than usual as I struggled to remain upright.  However, the heart rate variability is also somewhat greater than usual. At this pace, I would normally expect a value of RMSSD (root mean square of successive R-R intervals, a measure of high frequency variability) of around 5 ms, but RMMSD is in the range 10-20 ms during the periods of apparent sinus rhythm.  I would usually compute RMSSD over a longer period than 10 sec, so this value should be interpreted with caution.  Nonetheless, it suggests excessive parasympathetic activity.    Thus my provisional (and very speculative) interpretation of the rhythm during this period is of a series of premature atrial contractions occurring against a background of sinus rhythm with excessive parasympathetic activity. 

R-R tachogram showing apparent premature atrial contractions interspersed within sinus rhythm

Secondly, on several of the occasions when I had recorded apparent AF, the average pulse was as low, or lower, than that expected for the pace.  It is hard to imagine that a chaotic rhythm could pump enough blood to allow me to continue to run comfortably without any increase in overall rate to compensate for the inefficient ventricular filling.

With these uncertainties in mind I sent two of my tachograms to George – the one showing interspersed periods of apparently near normal sinus rhythm, and one showing a net decrease in rate.  He was kind enough to search through his own records and produced a similar record which included periods of normal sinus rhythm interspersed within chaos.  On account of the fact that his AF episodes are symptomatic, he was quite confident that this was not AF.  He was also able to reassure me that overall rate would certainly increase rather than decease during true AF.  Meanwhile Henry Szwinto, who had commented on my post of 5th June, had also sent me some traces of his experiences with AF while racing – confirming the dramatic increase in HR during AF.  As an aside, Henry achieved 2:41:11 in the London marathon this year and was 3rd placed in the 50 year old veteran group.

So in this roller-coaster experience in which the evidence has swung to and fro, the pendulum is now swinging away from a diagnosis of AF, though I think that the evidence does suggest that I am prone to premature atrial contractions.   There are still a few puzzles.  Why did the early evidence indicate a strong association with use of the salbutamol inhaler which I use to control my asthma?  As the evidence of chaotic rhythms has continued to accumulate, it has become clear that salbutamol was only associated with chaotic rhythm in winter. On some occasions when I had used salbutamol, I had noted in my log that the paths were icy, as in the run depicted in figure 1.  Perhaps freezing temperatures increase the risk of both wheeziness and poor electrode contact; or perhaps salbutamol increases the risk of premature atrial contractions.   

At this stage I am fairly optimistic that I do not have AF.  I am still on the waiting list for a 3 weeks continuous ECG recording and I will await the outcome of that before attempting to reach a definitive conclusion.  If the picture is still ambiguous after that, I will happily accept that some uncertainties in life are inevitable, and it would be foolish to limit ones activities for fear of vague uncertainty.  The simple fact that elderly men have a substantial risk of AF already places me in a high risk group, and ambiguous evidence from a heart rate monitor scarcely adds to the level of risk.

With regard to the question of whether or not my HRM is a boon or a curse, I am fairly sure the answer is that  a trustworthy HRM with the capability of recording R-R tachograms is a boon – although my unreliable RS800cx has been something of a nuisance.  I did not send it back to Polar last week because I was eager to acquire as much information about both the behavior of the monitor itself and the behavior of my heart before relinquishing it, but I will send it back this week.

The important issue that this episode of chaos has brought home to me is the fact that for an elderly runner, the risk of AF is appreciable, and the consequences potentially serious.   Furthermore, the experiences of George Newton, and others who have learned how to monitor their heart rhythm in an intelligent manner, is that paroxysmal AF is not necessarily an enigmatic mystery, but might be amenable to control. 

And finally, while the association between endurance training and increased risk of AF remains a subject of debate, it seems to me very plausible that the sustained autonomic imbalance associated with over-training is likely to play a large role in determining whether AF becomes an intractable problem or resolves relatively harmlessly.  I will return to a more detailed discussion of this issue in further posts, but meanwhile, I am more impressed than ever by the importance of avoiding over-training.  So far, the evidence suggests that systematic monitoring of autonomic function by recording both HR and HRV is a useful way to minimize the risk.

So the answer to the question posed in my last post is that my particular Polar RS800cx was indeed something of a nuisance, but despite this, it taught me a lot, and I have little doubt that a reliable HRM with R-R recording capability is a worthwhile investment for any ‘serious’ elderly athlete*.  

* For monitoring autonomic funtion via measurement of HRV to minimise risk of over-training; not for diagnosing AF, which requires  a clinical-quality ECG recording interpreted by a qualified person.

 References

[1] http://www.afibbers.org/conference/session52.pdf

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16 Responses to “Rollercoaster”

  1. John Bedson Says:

    Your latest chart does not look like Atrial Fibrillation to me. If it is showing premature atrial contractions then I would observe that they are a long way from the sinus rhythm and therefore your atrial refractory period must be rather short, which is not a good thing. It needs to remodel to get those vertical peaks a lot shorter. The longer your refractory period the more ectopic beats will be prevented from causing heart beats at the wrong time because the atria will not be able to conduct the beat and it will not be able to sustain a re-entry arrhythmia.

    If we are looking at a chart produced by a faulty polar monitor then all bets are off and we need to see what a replacement model will show. George Newton is the expert on these things; I have never seen a chart like the one you have just posted.

    I note that there are some places where the line is horizontal for a while. In an R-R heart rate chart you should not be getting horizontal lines as each beat should be at the very least slightly different to the previous one, so horizontal lines are impossible. This might suggest a fault on the polar monitor or perhaps a lack of conductivity between your skin and the wearlink strap? I have seen loss of connection give all sorts of weird readings. – Sometimes the curve goes horizontal, sometimes it drops to 35 BPM and stays there and sometimes it gradually slows down to 35 BPM over a prolonged period of time. I have also seen the line jump about with lost connection, but not to the degree on your chart. You could experiment by deliberately breaking the connection in different ways and see what sort of reading you get on the chart when you know for sure that the connection has been interfered with.

    Maybe try using ECG gel to improve the conductivity or use tape to increase adhesion to your chest. Shave the hair on your chest to expose more skin to the strap electrodes. Keep the strap uncomfortably tight. If it is comfortable it is too loose and you are going to get artefacts. Perhaps that is what this scare has been all about, either artefacts or a faulty monitor?

    • canute1 Says:

      John,

      Thanks for your comment.

      As you imply, the first issue is establishing whether the abnormalities in the recording are due to the abnormalities of my Polar RS800cx. Even if the abnormalities are not due to an intrinsic fault in the monitor, it is also necessary to consider that they might be due to poor electrode contact, despite my efforts to ensure good contact.

      I do not think the apparently horiziontal sections in the parts of the trace which appear to be sinus rhythm is a problem. In fact there are only three instances in that trace where the intervals between consecutive pairs of beats differ by less than a millisecond. On the contrary, there is actually more variability than I would expect. I was above the first ventilatory threshold at that time. Usually parasympathetic input has been almost entirely withdrawn by that stage, and RMSSD is typically around 5 ms. However, the observed value of RMSSD of around 15 ms indicated more high frequency variability than would normally be seen above first ventilatory threshold, suggesting more parasympathetic influence than is usual for me at that heart rate.

      But the major issue is the nature of the spikes. If they are premature beats, then, as you say, they indicate a short refractory period which would be a significant concern. Fortunately it is rare for me to get so many short beats so I hope this is not an enduring problem.

      Thanks for your addtional suggestions about ways to ensure good electrode contact.

  2. Jerry Griffin Says:

    I’m 70 yrs old; run between 5 and 50 mpw; do intense hill and steps work; row (indoors); bike; swim; and do kettlebells.

    My experience with the RS800X is extremely mixed.

    To me, the operative words in your post are “a trustworthy HRM with the capability of recording R-R tachograms is a boon –”. After five years of experience with Polar — several different models — I’m simply convinced that the device is not trustworthy. I get reading such as you’d had, with considerable frequency. Returning the device for servicing hasn’t helped. I’ve resigned myself to getting bad data at least once a week, sometimes more. And when I added the GPS capability, things only got worse.

    I seriously doubt you have AF. But if you do — and I hope not — I wouldn’t expect the RS800X to give you reliable data about it.

    Jerry Griffin

    • canute1 Says:

      Jerry,

      I hope I am still as active at 70 as you are.

      I suspect you are right about the unreliability of HRM measurements. Although my particular HRM clearly has some faults, I suspect that even after it is fixed there will always be a problem of ensuring good electrode contact. Therefore I do not think the HRM is a good device from making a definite diagnosis of AF. At best it is provides a warning of a potential problem. Further investigation is required to make a reliable clinical diagnosis

      However, my experience so far is that the quality of resting state data is usually quite good. Resting state data can provide potentially very useful data about level of recovery.

      The intriguing question is whether the data collected while running is a useful guide to adjusting training intensity – and I do not have an answer to that yet.

  3. John Bedson Says:

    I’ve managed to produce a chart very similar to the one posted above. I did it by deliberately breaking the contact between the wearlink belt and my skin after a night’s sleep when my skin and the belt was dry and contact could not be re-established. I’ll email it to you.

    • canute1 Says:

      John,
      Thank you very much for your experimets on my behalf. I will look forward to examining the data you send me.

      Although I always moisten the belt thoroughly (and sometimes use electrode gel) it is noteworthy that the crazy trace that I had posted was acquired on a freezing cold day. It is likley my skin was much drier than usual.

  4. John Bedson Says:

    One way to establish if you do or do not have AF would be to get hold of an Omron portable ECG. I have my own and they are quite inexpensive to purchase. Many doctors will lend you one for a few days. When you suspect that you might be in AF take a 30 second trace and look for the P waves. If they are absent you are almost certainly in AF. If the P waves are there you have nothing to worry about. P waves can only be seen on your computer screen with an Omron, the charts on the LCD are too small to show P waves.

    • canute1 Says:

      Thank you, John.
      I agree that identifying the presence or absence of p waves if the crucial test. The problem (or perhaps good thing) is that my possible AF is so elusive that it is extremely rare that I have any inkling it is occurring until after I upload the R-R trace to my home computer. The only occasion when I detected an apparently abnormal high heart rate at the time, manual palpation of the pulse revealed no abnormality. I think the best hope of a definitive test is the 3 week recording, but I am still waiting for that.

      So far the only fairly clear conclusion I can draw about my heart rhythm is that I do get at least some premature atrial and ventricular contractions. I occasionally detect short inter-beat intervals (probable PACs) and even more rarely, missed beats (probably PVCs) on manual palpation. But these irregularities are generally very rare, perhaps even less common than in the average man of my age. On the other hand if the sharp spikes shown in the recording I posted recently on my blog are PACs I think I do have a problem that needs addressing, since many of the spikes appears to represent inter-beat intervals around 250ms and I think even occasional episodes of frequent PACs as premature as this would probably place me at risk of AF. Some of these spikes look like PACs; other look more like artifacts. So at this stage I am eager to clarify the nature of the sharp spikes. Maybe the Omron would allow me to do this, though even the episodes of frequent spikes are rare, so I am inclined to wait for the three week recording.

  5. Ewen Says:

    Canute, I hope you eventually come up with an answer – and hopefully it’s a problematic HRM. On the cold weather readings – I get the same thing with my RS200. I’ve taken to soaking the belt in warm water on cold days (and wearing it tight) which seems to help.

    I’m thinking now I wouldn’t buy a monitor for HRV use if it’s only usable in the resting state.

    • canute1 Says:

      Ewen,

      Thanks for your comment. My experience is that a HRM with the capacity to provide measurements of HRV provides a wealth of intriguing information, both at rest and during exercise. However the interpretation of that data is treacherous. First of all, there is the problem that readings might be unreliable if electrode contact is not good or there is external interference, but even when it appears that electrode contact is good and there is no obvious external interference, there are many enigmatic observations.

      The evidence from research reveals that current theories regarding HRV during exercise are inadequate. The question of whether or not a large amount of high frequency heart rate variability (HF HRV) is healthy or unhealthy is unanswered, though on the whole I think that the available evidence indicates that a large amount of HF HRV during exercise is generally an unhealthy sign.

      My own observations suggest that an increase in HF HRV when exercising in the upper aerobic zone is an indicator that I am developing a viral illness or some other problem. On balance, I personally find the HRV data from my Polar RS800CX is a useful training aid, but it must be interpreted with great caution, and I would be very cautious about recommending it to anyone else.

  6. Ross Says:

    Very interesting reading. i have recently had to upgrade from the Polar Vantage NV to the RS800CX. I have had a lot of problems with the RS800CX misregistering and giving crazy high readings o the HR profile. With the Vantage NV I got mostly dropouts, but occasionally high readings (round 215-225 bpm). I sent the RS800CX back and after 3 belts and two senders the problem had reduced markedly. In the weekend I ran a marathon with the R-R recording on. The marathon went steady – cruise mode to 30 km, and moderate strain from there in. The pulse file looks smooth, but the R-R shows from 30 km huge variations – from 220 to 30 bpm. I would like to put it down to a faulty product, but have had incidents of AF-type behaviour. I would suddenly feel lousy while running, (like indigestion) and when I glanced at the pulse it would be over 210 bpm. When it happens during a race I am reduced to walking for a few minutes until it goes over. The pulse switches back to normal suddenly, at the same time I feel well again. I can then run on as usual, and have caught again the runners who have passed me. Feeling the pulse manually feels like it is racing irregularly. Although the weekend’s marathon didn’t have any bad feelings, it would be interesting if the RS800CX was detecting incipient AF – even better if it could be a tool to help me avoid it. But I will try again with Polar to see if it is a product problem

  7. Arthur Gibson Says:

    Ross: See my blog at: http://www.network54.com/Forum/669782/ for help in interpreting Polar HRM data. If you send me your Polar file I will give you my opinion on your results. But you must have “Correct data automatically when downloading exercises to software” unchecked when recording so that the ectopic beats show up clearly and are not edited out of the charts before you can examine them. (Options/Preferences/Hardware/Options) Afib is not a benign condition; I have had it for ten years and it must be treated early or it will get progressively worse. Wearlink belts need to be replaced every 1-2 years. They need to be washed often to get accurate results. Electrode gel should be used for conectivity, not water, despite what Polar say to the contrary. Once a week yu need to wash the electrode gel out with dishwashing liquid and water. Otherwise you might get junk on your charts.

  8. Ross Says:

    Thx arthur, that was very informative. Unfortunately I had the altimeter on, as it was a 3 lap course with distinctive hills that are more reliable than the km markings. I see now that the altimeter recording reduces the resolution of the R-R recording (I was not aware of that). I plan to send the HRM in to let Polar do a troubleshoot of it again, but can try and generate some more traces when I get it back.

    I turned the autocorrect function off, as I wanted to see how bad it was before correcting
    I noticed also that drinking too little water could be a factor – I drink very little (compared with coworkers who seem to constantly have a teat-bottle to suck on nearby). I’ll try a period with regular drinking

    I got the HRM monitor in august, it malfunctioned from the first use, I changed both batteries at once, and have had the belt replaced three times by polar (and the sender twice. I wash the belt after most trainings, but don’t use gel – as I don’t believe it would last a 3 hr run with sweating.

  9. Ross Says:

    Hi again! a little confused here, that link took me to John Bedson’s blog, and I didn’t find an address for Arthur Gibson. My address is rossinarvik ‘at’ hotmail.com.

    I had a look at the zoomed in R-R profile. Looks like electronic noise to me.

    I had 5 sec averaging, altimeter turned on, and auto correct turned off. I have trouble understanding how the altimeter affects the resolution – I thought it either recorded each beat or it didn’t, or is it recording other information between the beats??

  10. Arthur Gibson Says:

    My email address is: bedson@pacific.net.au

    You need 1 second averaging.

    I don’t know if the altimeter will affect the R-R recording, although I doubt that it would make any difference.

    Sometimes the Wearlink does not “link” with the receiver for a long while and it records garbage. But I can tell if it is ectopic heart beats or garbage. Garbage is jerky lines up and down, but not vertical lines. Send me the file if you want and I’ll let you know what I think.

  11. canute1 Says:

    Ross,
    As John Bedson remarks, AF is a serious matter. When it only occurs intermittently, it can be difficult to diagnose. However your description of transient symptoms accompanied by an irregular fast pulse indicates the need for further investigation. The Polar HRM can provide important clues. I think that John Bedson and George Newton have developed great expertise in interpreting Polar traces in many circumstances, and I am grateful for what I have learned from them. However my experience suggests that the Polar RS800CX is not reliable enough when used while running, to provide a reliable diagnosis of AF in cases where the only episodes occur during running. I think the most reliable device is a device such as Spiderflash which is capable of recording a good quality three lead ECG during vigorous exercise. The Spiderflash is extremely expensive, costing thousands of pounds

    I was able to get a three week Spiderflash recording done under the National Health Service, last year, though I had to wait about 6 weeks for the device to be available. I am completely confident that I did not experience AF during this time, and furthermore I do not think there is any substantial evidence that I have ever had AF. However I am pleased that I have been alerted to the relatively high risk of AF in elderly athletes. Now I know what to look for, I am not worried. I remained satisfied that despite the somewhat increased risk of AF in runners, the overall health benefits of running outweigh the risks.
    .
    The Spiderflash did confirm that I had one brief episode of tachycardia (a flurry of 5 fast beats) during the three week observation period. This is well within the normal range for a 65 year old. I see occasional similar flurries of 3-5 fast beats in my Polar recordings, and I know that these are no cause for concern. In addition I still do get intermittent very sharp spikes in the Polar trace. I think it is almost certain that these spikes are artefacts though I have not been able to exclude entirely the possibility that these are premature atrial contractions.
    I continue to use the R-R recording so that I can keep an eye on the occurrence of the occasional flurries of tachycardia. So far they have remained rare. If they were to become more frequent, I would look into the circumstances that produce them as I think it that increasing frequency of these flurries might be an early warning of unhealthy atrial excitability.

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