CPET

Does anyone know if a cpet is accurate if you are paced.  I'm mostly curious because they did not change my settings for the test so I went into pacemaker weinkebach before I hit anerobic threshold.  I am pretty sure they use you max heart rate to calculate you VO2max, and mine would show an artificially low heart rate due to the wienkiebach(I am sure I prob misspelled that twice). I had to show it to the nurse post test and explain because during the test she exclaims "wow your heart rate went way down now, your doing great". I had already explained upper rate limit with her prior to test and she had already forgotten.  Or course my atria were going twice as fast likely putting that rate between 200-220bpm if it was true 2:1.


6 Comments

Wenkebach

by Julros - 2021-03-17 02:14:24

Many of the Wenkebach rhythms I have seen are more like 3:2. Typically, you will see a P wave (atrial contraction) followed by a normal interval then a QRS (ventricular contraction). Then another P wave with a longer interval before the next QRS, and then a P wave with no QRS. Then it goes back to a normal interval, longer interval, then missed QRS. 

2:1 sounds more like a second degree type 2 block. 

Wenckebach and other arrhythmias

by Gemita - 2021-03-17 05:23:26

Asully, 

With due respect to the nurse on duty, whoever is finally responsible for the analysis, interpretation and accurate reporting of your CPET tests, will be highly qualified in this area, will have seen many examples of rhythm disturbances during this complex procedure and will be able to give an accurate assessment of your exercise ability based on what they actually see.  He/she will understand the effects of pacing and arrhythmia on your final results and will no doubt report all the relevant findings to your EP. 

In many ways I would say it was a blessing you had the disturbances present when you were actually tested (how often does that happen) to show them clearly what you are up against.  This will surely help with any settings adjustments?

Also, if they had changed your settings before the test, would this have given them a more accurate picture of how you perform with the settings you do have?  I don't think so.  I would be reassured that the test was valuable and will have given them vital information about your heart and your capacity to exercise with your current device settings.  If they need to, they can always re-test using different settings, asking different questions.

I hope your new EP will be able to help you.  I would be very interested to hear the results of your CPET when these are available. 

Accuracy of CPET

by Selwyn - 2021-03-17 07:00:05

CPET ( cardiopulmonary exercise test) tests the cardiovascular system  and lungs during exercise if you are physically able to use your limbs effectively. 

Of course, the accuracy of the test is limited by the sensitivity and specificity of the measuring apparatus, your psychology, and your physical ability. 

Having said that, then you have to ask yourself why was the test requested, and what are you hoping to find?  Rubbish in - rubbish out!

The maximum heart rate on exercise ( 220-age) is not likely to be reached unless a pacemaker is set up for that upper limit.  An arrhythmia , such as you describe, will limit the attainment of maximal heart rate.

This arrhythmia will produce a lack of oxygen ( presuming the person is able to physically exercise the limbs ), breathlessness, and an inability to continue. Any failure of cardiac output produces a similar scenario.

Similarly, lung disease will limit the amount of oxygen available for exercise and the person will desaturate their blood of oxygen and be unable to continue. 

What is measured?

Heart rate
ECG
Blood pressure
Oxygen saturation
Respiratory rate
Minute ventilation (amount of air that the patient breathes in a minute)
Exhaled carbon dioxide concentration
Inhaled and exhaled oxygen concentration

Your maximum oxygen uptake ( VO2 max) can thus be calculated.

The CPET is not a mountain to climb ( pass or fail?), rather a look at how efficiently your engine is performing. All components must work together for the best 'performance'.

I trust you were suitably exhausted by the test and could no longer continue? If so, it has been a successful test ( I don't see accuracy being relevant)t. I hope the effort was worthwhile.  I would suggest your outcome is limited by your heart ( arrhythmia) rather than your lungs from the information you have supplied. This would then explain your problems on exercising. . As I say, rubbish in- rubbish out.

 

 

Calculated VO2max is just that - calculated

by crustyg - 2021-03-17 08:58:41

Perhaps I'm missing the point here, although Selwyn does a great job of explaining the factors.

Any proper test that measures O2 consumption is actually capable of measuring VO2max as opposed to the common *calculated* or derived VO2max estimations.  So if you were wearing a proper gas-exchange rig whilst exercising then your VO2max was measured.  If not, then it was just estimated from other numbers.

Was it truly maximum?  Probably not.  Most of these tests (like the dreadfully non-physiological Bruce Protocol) are designed to be open-ended within an acceptable timescale.  Bruce takes you up a steeper and steeper effort gradient to ensure that everyone has to stop within the booked timeslot.  A truly physiological test approaches max-capability in ever smaller steps, as even a 1% increase in required effort can push the body over VO2max and into anaerobic metabolism.  Even a bleep test gets tougher as it goes, again to be open-ended (there is no set limit that some Olympians might be able to sustain).

OK, so it wasn't a true maximum: does it matter?  Depends on what the question was being asked that made a CPET worth the effort (yours and theirs).  Tim Noakes summarises a lot of VO2max against time and age in his bible (it goes down, and the higher it was the steeper the decline against age!)

Much more important is what your performance was against any previous data for you.  Slightly less important is your numbers against the expected for age/sex.  And as Selwyn explains so well, lung function is just as important as cardiac output, and for *some* folk with heart problems there may be associated and related (or not) lung condition.

Sewlyn and crustyg

by asully - 2021-03-17 12:46:04

I am so glad you jumped in, I didn't want to call you out in the post but hoped you would respond.  As for what they are looking for it was done as a prognostic test for my advanced hf/transplant/LVAD doctor.  The possibility of going on the UNOS list came up at our last appointment, and I have not had a prior CPET test.  I have done a standard Bruce protocol test in the past but that was ordered in error by a cardiologist I no longer see (he was supposed to order a cpet).  So I really don't have any comparative tests (the Bruce protocol test obviously couldn't be completed due to the inability to reach max predicted heart rate, and terminated due to near syncope after holding 14 Mets for two min).  This was the standard CPET, with the mouthpiece, ekg, and blood pressure monitoring.  The nurse choose not to do the "modified" slower version on me due to my age (34) and overall decent physical fitness despite several systolic HFREF. I lasted 6.5 minutes and reached 9 METS.  When it was done I asked the nurse if I had achieved anerobic threshold during the test, she said I did (however I am not sure how reliable her answer was).  I wanted to know because in the papers I have read if you don't reach anerobic threshold the test is suboptimal and then is generally based on peak VO2 instead of true VO2max.  I have since yesterday read a paper that explains that using the standard protocol instead of the gradual increase one can lead to overestimation of peakVO2 in HFrEF patients (which is mildly concerning, although they can always test me again).  I am still waiting for the full test results but a medical assistant from the doctors office who called last night was able to see that some numbers had been entered and she told me they had entered peakVO2 at 20, which I believe she said was 56percent of predicted value (I may be off by a percent or two).  The VE/VCO2 slop had not been entered yet so I clearly have to wait for the entire test results.  I have also read that this can be of better prognostic quality than peakVO2.  If my peakVO2 is 20 this is well above listing criteria for UNOS (which could be considered good or bad depending on how you look at it).  I suppose I don't really have any specific questions, but I personally like to review all my tests and make sure mistakes aren't made.  This has helped me in the past, for example when my mitral regurgitation was severely underestimated because it was an eccentric posteriorely directed jet with low velocity, and helped me get to the appropriate specialists who were able to to asses things better and luckily act in time.  Knowing what all the test results mean and how they work also help me have much better conversations with my cardiologists, since they do not have to just give basic answers.  I will probably be back on here asking more questions about the results once the full test is released, hopefully y'all won't mind answering some questions.  Thanks for all the responses!

CPET?

by AgentX86 - 2021-03-17 22:44:41

I'm wondering how CPET works for those of us with CI?  Obviously it's done but how?  I suppose it makes sense but beats me how.  Maybe you can help me out, Crusty.

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I've seen many posts about people being concerned about exercise after having a device so thought I would let you know that yesterday I raced my first marathon since having my pacemaker fitted in fall 2004.