Pacing percentages and AV block

OK, I admit I'm confused. I am coming up on one year with a dual chamber Medtronic PM...Implanted due to complete AV block and since diagnosed as 2nd and 3rd degree heart block.

My 3 month transmission was sent on 4/30/2021 and I just heard from my clinic on my results. I was told that Atrial pacing - 24.5% and Ventricular pacing- 1.2%.

No arrhythmias.

My confusion is on this..If I have some degree of AV block, shouldn't the ventricular pacing be the highest percentage ? What am I missing here ? Or is the atrium pacing the ventricle ? 

Also I've been having some palpatations and SOB, very inconsistently. I told the device nurse this but she didn't seem concerned.

Can anyone explain, in simpliest terms possible...:)




Pacing percentages v diagnosis

by Persephone - 2021-05-11 00:08:16

Hi DixieC - I don't have a technical explanation to offer, but I do share a fairly similar experience / confusion of being diagnosed with 2-3 degree block yet having significant atrial pacing.  I will try to find out more about what may be going on when I eventually have a cardio appt - it's been almost 2 years due to covid, etc.  However, I feel great with my current pacing situation and so try to keep that foremost in mind.  I hope you're continuing to feel well, also.

Yes all very puzzling but you do have bradycardia as well

by Gemita - 2021-05-11 05:22:15

Hello Dixie Chick 65,

I agree with you, with your original diagnosis of ?complete AV block, your pacing results seem somewhat puzzling and I would have expected to see a higher pacing % in the right ventricle instead of in the right atrium.  However, based on your latest figures, you still needed that 1.2% right ventricle pacing which may not sound much but it was still necessary.  Also this figure, with any electrical disturbance can be expected to change at any time so you have your pacemaker to protect you and support you when you most need it.

Additional thoughts are as follows:

1. AV Block is an electrical disturbance and like with all electrical disturbances, it can be variable and the situation can change rapidly.  I recall initially you had some high ventricular pacing figures, perhaps as high as in the 80% range?  You may find your future results will show a sharp increase in your right ventricle pacing percentage.  Variability can be normal and that is one possibility.  

2. Another possibility is that the original diagnosis may have been questionable or caused by a specific acute condition which has either been treated or has now largely resolved?  

3. Thirdly, Dixie Chick remember that you do have bradycardia as well, so I would expect a fair amount of atrial pacing, depending on your minimum heart rate setting.  If like me for example you increased the rate from 60-70 bpm you could expect a higher atrial pacing figure.  Conversely, reduce your rate from 60 - say to 50 bpm - and your atrial pacing figure might decrease.  Percentage rates are going up and down all the time and really aren't important.  What is important is how we feel.

Either way, I think you need to direct this question to your doctors Dixie Chick. They are best placed to answer this.  I see they have revised your AV Block diagnosis?  I would be asking some questions like if the pacemaker is working properly, if both leads are functioning as they should?  Could that be an explanation for the puzzling pacing percentage figures or for your symptoms - palpitations and SOB?  These symptoms are clearly new and need explanation.

Keep an eye on your SOB and palpitations. The nurse may not be concerned, but you clearly are, and not without good reason.  If your palpitations cause SOB (shortness of breath) this might be significant for an arrhythmia and we all know that an arrhythmia can be difficult to detect without long term monitoring.  (I note no significant arrhythmia was seen or recorded by your pacemaker for the period monitored), but this doesn't necessarily mean that you had none.  It may just mean that the pacemaker is not set up to record certain benign arrhythmias, like ectopic beats or any event (arrhythmia) below a certain heart rate and duration.  

Alternatively I would pop along to see your general doctor for a few health checks if the clinic feels your palpitations/SOB are not pacemaker/heart related?  There are quite a few causes for SOB, so do not delay seeking advice.  

I wish you well, as always Dixie Chick

Pacing percentages

by Dixie Chick 65 - 2021-05-11 07:48:55

Thanks Persephone and Gemita for your thoughtful replies...Yes, for the most part I feel very well and that I am thankful for ! Gemita you are correct that I did have bradycardia and a high ventricular rate at first. At four weeks from implant my VP was 93%. Then amplitude and pulse were 3.5 to get my heart used to being paced, I was told. After that, they were dropped quite a bit and my pacing percentages have also lowered.My low setting is 60 and high is 130. My 1/21/2021 percentages were AP -14.8% and VP 0.2%. My doc did tell me that the numbers will change all the time. I'm just confused about why the atrium has the highest amount of pacing if the SA node is working. 
I remain very grateful for this technology - I'm just trying to understand the basics !

Thanks for taking time to reply !

SA Node and Bradycardia

by Gemita - 2021-05-11 08:02:18

Dixie Chick, I have bradycardia and the SA Node is definitely lazy and not working properly and perhaps you are experiencing this too - hence your pacing figures?  It sounds to me, for the moment, as though your AV block is less of a problem than your SA Node, but these are great questions for your EP.  I would go back for perhaps a revised diagnosis and ask whether the problem is also related to the SA Node?

Yes I agree confusing

by quikjraw - 2021-05-11 09:22:19

Hi Dixie Chick

Looking at the settings you posted in the gallery your pacemaker was set to DDD mode. 

The minimum heart rate is 60bpm in your settings. In the absence of Rate Response being turned on the only way I understand your atrial based lead pacing would be if your heart rate dropped below 60bpm. 

So it would appear that around 24% of your 24 hour day your heart rate is trying to drop below 60bpm. This is roughly 6 hours so it could be that this is happening during sleep. 

The Ventricle pacing of only 1.2% is more difficult to explain. This equates to roughly 20 minutes of ventricular pacing a day. 

As already discussed by Gemita above your block may have improved by some margin. It may also be possible that your block at this stage is more of an issue at the lower heart rates and as the atrium now will not beat below 60bpm it could be helping you. I am not a medical person by the way so please do not take what I am saying is gospel.

Was your lower heart rate level ever changed to 60bpm or has it always been like that?

I notice you have a fairly long AV delay set on our pacemaker (much longer than mine) I do not know if they have done that to reduce unnecessary pacing or for another reason.

I hope some of that helps

thanks John




Pacing percentages ???

by Dixie Chick 65 - 2021-05-11 09:41:33

Yes, John my lower rate has always been 60. I've also been told I have intermittent heart block, when it was first thought to be complete heart block. My settings have been adjusted several times, trying to optimize everything. As I understand it, the docs like to minimize ventricular pacing. I've noticed my delays as well and they started out at 150 and 180, paced and sensed. They are now considerably higher. Other than a few periods of SOB and high heart rate, I'm feeling very well. Just a little concerned about what those mean for me long term.

Thanks so much for your input !



Picking Up Arrhythmias on Pacemaker Monitor Reports

by Marybird - 2021-05-11 15:20:06

I'm an amateur myself as far as  the technicalities of all things pacemaker, so can't say much about the why's of increased or decreased percentages of atrial or ventricle pacing, though I always learn from reading everyone's input at this forum.

I just wanted to mention, though I'm sure you already know, that you can have tachycardias, palpitations all day long and they will never be picked up on pacemaker monitor reports if the HR threshold is set above the heart rate at which your tachycardias occur. I think the default tachy detection setting ( or alerts, for some pacers) is around 170-180 BPM, and if your tachycardia HR is less than that, nobody will ever see it.

When my EP adjusted my pacemaker settings at the 6 week post-implant visit, he went back to my pre-pacer monitoring reports over several years, and noted that the tachycardia demonstrated on those reports would reach around 140-150 BPM. So he adjusted the tachy alert to 140 BPM, down from 180. He also adjusted the maximum pacing rate down from 130 to 120, to avoid overlap or interference with the tachy alert ( something like that). I used to get higher tachy rates ( around 200) but I think all the medication I take has put a "governor" on my heart rate ( as the cardiologist's PA I sometimes see put it) so it's lower now. They have picked up tachycardia on my remote monitor reports ( some of it afib, they said) with the lowered detection rate.

As Gemita suggested, if you continue to have palpitations or other symptoms suggestive of a tachyarrhythmia, a monitor study ( such as a ZIO patch or another type of event monitor) would be helpful in picking up the cause of the symptoms. And if they can document the heart rates at which those tachys occur, it might be a consideration to have your cardiologist lower the tachy detection HR on your pacemaker so in the future these can be picked up on your remote monitor reports.


Picking up arrhythemmias on PM monitor reports

by Dixie Chick 65 - 2021-05-11 15:45:29

Yes, I do have some settings to monitor AF/AT and VT. But as you say some of these arrthymmias may not be picked up. I’m going to be aware of all this and keep it in mind going forward.

Thanks !


Lower rate limit.

by PacedNRunning - 2021-05-12 04:12:32

Even though you don't have a sinus node issue but mainly heart block your lower rate limit may be too high and unnecessarily pacing you. I'm not sure if your active or Not but I would think unless your symptomatic with bradycardia they could lower your lower rate limit. I have high grade intermittent block and bradycardia but my pacer is mainly for HB since I'm not symptomatic with my bradycardia. They intially had my lower rate limit at 60bpm and I paced 71%. But since I don't need that pacing they lowered it to 45 for about a year and my pacing went down to 37%. I mainly pace at my lower rate while sleeping or sitting/resting.  Im Now at 50bpm as my low limit because my settings work better overall at 50bpm vs 45bpm  I still pace about the same 24-35%. So if your Not symptomatic with bradycardia perhaps they could lower it and limit pacing in the atrium. It's alway best to allow your own heart to work. At your initial paced delays 150/180ms I was pacing high also 100%. Now down to 200ms and much better since my own heart is able To do most of the work. 
But the Atrial pacing is based on how often you drop below 60bpm, which sounds like with sleeping. :) 

Lower rate limit

by Dixie Chick 65 - 2021-05-12 08:54:11

I am not symptomatic with bradycardia and haven't been since I got my PM. I am fairly active and my activity level on my Medtronic app averages almost 8 hours daily, most days. You make some good points ! I haven't even thought about my lower limit being changed. My next device check is scheduled for November and I really don't want to wait that long. I've been having some shortness of breath and fast heart rate off/on since the middle of April. I can't figure out what going on with that but my doc saw nothing too unusual in my 3 month data sent on 4/30. However I think the HR isn't going high enough to to kick in. My Apple smart watch says HR was 158 and low was 59. Don't know how accurate it is though. My AT/AF detection is set at 171 and 150.

I really appreciate your input on this, Thanks !


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