Back with a question (of course)

I'm baa-aaack! I have been feeling great and happy with life lately, and decided that I should just get on with life. I'm still doing well--eating better than ever and exercising more etc, etc. My cardiologist continues to reassure me that all is looking wonderful. I just happened to go onto my health network patient site for something or other and saw that the most recent report sent by my monitor was posted for me to view, so I thought I'd just take a look. It's mostly medical speak and way over my head, so I just look for battery life (over 11 years), "episodes" (0), and the description of my PM as "properly functioning" (yep). Something else caught my eye though, under a heading of % Pacing: The line for RA showed 75%. I vaguely recalled seeing this as much lower on past reports, so I went back & looked. Sure enough that line showed 56% about 8 mos ago. I tried a tiny bit of research into what that means, but I still don't really get it. Can some one dumb-it-down for me?? As a reminder, I had afib that was not well controlled with meds, cardioversion failed, ablation also not good, and shortly after that I began to have presyncope and was diagnosed with Sick Sinus Syndrome. Pacemaker took care of that and allowed me to take more effective meds (Metoprolol AND Dofetilide). Not thrilled with such heavy duty stuff, but no afib for 2 years now! So what is that percentage and why is it apparently increasing? I'm just curious as opposed to being worried enough to call the doc.


Nice to hear from you and welcome back

by Gemita - 2023-09-02 14:19:09

TLee, how nice to hear from you and to know that you are still well and with zero episodes of Atrial Fibrillation (AF).  Tikosyn and Metoprolol must be doing a good job.

Our pacemakers work on demand.  They give our hearts a set amount of time to beat on their own before they will intervene to pace us.  That means that if my heart rate goes below my lower set rate limit of 70 bpm and doesn't beat for a second or so, the pacemaker will send a signal to pace the right atrium. Then it gives the ventricles a fraction of a second to keep up.  If it doesn't, then it paces the right ventricle.  The pacing percentage is a reflection of how much each chamber is being paced.  How much we pace depends on our condition.  With complete permanent heart block we usually pace 100% in the ventricle, with sick sinus syndrome we usually pace more in the atrium.  If we have both sick sinus disease and heart block we could also pace up to 100% in both our right atrium and right ventricle.

What is your lower rate set at?  For example my lower rate limit is set at 70 bpm and I am 100% paced in the right atrium. My own natural resting heart rate is something like 30-35 bpm, so you can imagine with a lower rate limit set as high as 70 bpm, my pacemaker is working all the time, hence 100% right atrium pacing.  Reduce my lower limit heart rate setting and my own natural heart would be forced to do more of the work.

You have Sick Sinus Syndrome.  A pacemaker will keep your lower rate limit setting stable so that you can continue to safely take rate control/anti arrhythmic meds for your AF without your own natural heart rate falling to dangerously low levels.  

Why has your Right Atrium percentage pacing increased?  It could be due to several factors.  Your sick sinus condition could be progressing and you are requiring more pacing support.  Your medications could be reducing your own natural heart rate below your lower set rate limit and your pacemaker is therefore pacing more frequently in your right atrium to prevent your heart from beating too slowly.  It could be due to settings changes like an increase in your lower rate limit which means that you are pacing more.  It could be because you are exercising more and requiring more pacing support to keep up with your new energy demands.  So many things could affect your pacing percentages but as we always say, it is not the percentages that matter, but how we feel that matters and based on your post, it seems you are feeling extremely well.  

Out of curiousity, do you know how much you are pacing in your right ventricle by chance TLee.  Please have a look and let us know?  

Right ventricle pacing

by TLee - 2023-09-02 15:12:45

Right ventricle pacing is .03%. I assume that is good(?). Maybe once the atrium gets the nudge the ventricle knows what to do? You can see how I simplify, simplify! Yes, I am feeling really well--even my arthritic hip has benefitted from exercise and weight loss, and it had become a lot more physically and mentally draining than my heart issues. I even show a tiny improvement in lung function, so COPD is stable. It does sound like I have a lot that is "wrong" with me, but I don't feel that way!

Excellent - better than mine

by Gemita - 2023-09-02 15:41:45

TLee, .03% Right Ventricle pacing percentage is even better than mine.  It is more than good.  Actually you rarely need Right Ventricle pacing support so that tells me your arrhythmias are stable too.  I am pacing minimally also Right Ventricle around 2% but can be higher during a flare up of my arrhythmias.

Yes the right atrium being paced 75% of the time needs a bit of a nudge but still your own heart is able to keep up for 25% of the time based on your current settings, heart condition and other factors.  You don't have any block problems so the signals from the right atrium are getting through okay to the ventricles.  Everything seems to be working really well based on those percentages.  

Does that mean that you won't need a hip replacement?  And an improvement in lung function too is good to hear.  Weight loss and exercise may be helping the COPD.  Amazing progress and I hope it continues

RA pacint percentage

by AgentX86 - 2023-09-02 16:46:08

THe RA pacing percentage is almost a useless number, particularly just as a number standing alone. It's possible, at least theoretically to go from 0% to 100% RA pacing by changing either the heart's intrinsic pacemaker or the implanted pacemaker's rate by 1bpm.

Pacemaker work by using a timer to measure the time between two heartbeats. If the pacemaker is set to 60bpm, the timer is set to 1 second.  When a heart beat is detected, this timer starts counting down to zero.  If the heart beats before 1 second, it's rate is above 60bpm, so the pacemaker resets its counter to 1 second and starts counting again. If this were maintained, it would be a 0% pacing pecentage.

If the heartbeat doesn't come before 1 second, the pacemaker starts the heartbeat and resets the timer. The heart's pacemaker is now less than 60bpm so the pacemaker is in carge. This would be a 100% percentage.

Let's assume the intrinsic heart rate is 61bpm.  That would be 0.98 seconds between beats. From above, the timer would never expire because the 1 second timer would expire 0.02 seconds before the pacemaker started the pulse. If this continued, we'd have a 100% pacing percentage.

Now set the pacemaker to 62 bpm (0.096 seconds.  The pacemaker counts from 0.096 seconds to zero because the heart's natural pacemaker would have paced in another 0.02 seconds but the pacemaker got there first.  This would be a 0% pacing percentage.  We went from 100% to 0%, just by altering the pacemaker's settings by 2bpm.  Reverse this for the heart changing rather than the pacemaker.  The point is that it might not take much to change this number in a big way.

The LV percentage means more.  This is the numbe of atial paces (either generated by the SI node or the pacemaker) that don't make it through, or or too slowly, from the atrium to the ventricles. This indicates the condition of the AV node. This doesn't depend (much) on the heart rate. It is sensitive to other settings but these should be pretty constant. 0.3% is nothing.


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