Ventricular v atrial pacing

Hi all,

Hope you are having a good week so far.

I have had my call with the cardiologist today. Not much to say as they did not have my records to hand but hey ho.

My settings were changed in December from a lower heart rate of 60 to 40. They also changed the PR interval wait time to 500ms (I have a long PR as well as 2nd degree heart block).

In December my percentages were Atrial 23 and Ventricular 46.

Now with the new settings for a few months it has now gone to <1% Atrial but 80% Ventricular.

I thought they said that in December the pacemaker would wait for a few dropped beats before pacing but maybe I have misunderstood and it is still waiting an amount of time and then pacing.

I know I should not worry about amount of ventricular pacing but is there still any point in me trying to have the settings tweaked again to reduce the V%? 

If all else fails would it be worth me asking them to increase the atrial back to a higher level which will increase Atrial but lower Ventricular rates? I assume there has never been any issues reported with pacing of the atrial?

It would appear that at higher heart rates during exercise I still have 1 to 1 beats so that is good news.

Thanks John


My thoughts

by Gemita - 2021-02-24 16:29:59

John, I would ask myself do I feel better with my present settings?  If the answer is yes then I would respectfully leave well alone.  I think we sometimes worry too much about our numbers when all we really want is to feel better.  Supposing you start adjusting those settings, get really outstanding results with lower ventricular pacing but you feel absolutely awful, what would the benefit of that be ?

Either your condition has worsened (progressed) or your changed settings has made your heart more dependent on ventricular support but if you feel well with your current settings, then does it really matter?  Isn't that what we aiming for:  a symptom free life and support when you most need it.  

If however you are not feeling well or you still feel that something is not quite as good as it should be then yes go back and start a dialogue of understanding where adjustments could be made.  I wouldn’t necessarily be happy with those numbers either if you are having symptoms.  Your PR interval - what was it initially set at?  It does seem too long.  I still think your heart rate is too low as well.   It sounds as though you don't want any support at all from your pacemaker, as though you are still questioning the need for it, but perhaps I am mistaken.  Forgive me if I am.  It seems to me with those settings a block is more likely to occur, triggering an increased need for ventricular pacing.

Did your doctors offer any explanation for the increase in ventricular pacing, John, although I note they didn't have your records to hand.  That doesn't sound very reassuring. 


John the above link (don't know if there is anything more recent assessing atrial versus ventricular pacing benefits?) might help to answer your question.  We all clearly know about the potential dangers over time of increased right ventricular pacing and potential for it to lead to heart failure in a (hopefully) only minority of individuals due to dyssynchrony between chambers, but I really don't know what the potential dangers are of increased atrial based pacing over time.  Maybe there is a risk?  I am paced (and have been since early 2018) almost 100% in my right atrium now, with only minor ventricular support - maybe up to 5%.  My AF and other arrhythmias are certainly better controlled so it has been a very positive improvement for me.  With your block however, you will always need ventricular support, so I wouldn't worry about those % too much.  If you need support, you need it 

Ventricular pacing

by Selwyn - 2021-02-24 16:39:54

Pacing with two leads ( atrial and ventricular) ensures coordination of your heart. The problem of an uncoordinated heart is a decreased tendency to the  maintenance of  adequate cardiac output, increased  mortality, occurrence of atrial fibrillation, strokes, heart failure and pacemaker syndrome. Dual lead pacing  particularly helps  in those  with some intact AV conduction, and improves exercise capacity.

I think I would be happy to have normal pacing (Dual lead sensed and paced) . This is most likely to ensure your well being. 

Ask for a copy letter of your  telephone consultation ( GP letter), in that way you will ensure proper records are kept and better luck next time!



by AgentX86 - 2021-02-24 21:52:59

Normally this stuff doesn't matter much.  To paraphrase Therese, "Do you feel good, punk?  Well do ya'?".

Seriously, the numbers themselves don't matter much.  It is odd that reducing your pacing rate that your atrial pacing rate went down.  It's normally the other way around.  You don't say whether your PR interval was increased or decreased but that normally tracks too (higher delay = higher percentage).  Again it doesn't really matter that much but your EP will probably want to do an echo more often (as should you) but problems aren't the norm.  I wouldn't worry too much about it.  Many here are V-paced 100% of the time.

I wouldn't ask to have it changed back but would ask why it was done and what the long-term effects will/might be.  I'd not second-guess my EP's settings but I would certainly ask what to expect and why they were changed.

If all you want is to reduce your %V-paced...

by crustyg - 2021-02-25 06:19:50

..then get your LRL increased to 50BPM.

Whoever told you that your PM will allow you a couple of dropped beats before it kicks in was talking nonsense.  Your PM applies the rate limits that it's been set with all the flexibility of a stainless steel ruler.  1500ms after the last beat without seeing anything and your PM will activate the vent-lead - because your AV-node might be in complete block.  No deviation permitted, as reliable as night-following-day.

We're all different and I've lived for some years with a resting HR of 40-something BPM, but I'm very happy with my new, paced LRL of 50BPM.  I tried an LRL of 45BPM and had it changed back to 50 the very next day after a particularly nasty Pilates session (insufficient cardiac output).  There is a very small risk of increasing your LRL leading to raised BP but that's easy to check over a week with a home sphygmo - twice a day, same time, morning and evening.

A few things to think about there

by quikjraw - 2021-02-25 09:55:31

Yes I should probably explain myself a bit more.

The things I am worried about are.

1) Long term effects of ventricular pacing. (I'm 45)

2) That my pacing percentages are high not primarily due to my 2nd degree block but my long PR interval. (I have no evidence at all how much of the day my heart block is present, it could only be during sleep, it could be only 1% of the time)

3) If paced beats are occurring during exercise they are less efficient than intrinsic beats. It's early days (4 months after implant) but running is definitely harder.

I think there are arguments for me to have a raised lower limit to see if that can reduce the ventricular load but I did think at the time with a 60bpm lower limit that I was struggling to sleep but i'm still waking up in the night anyway.

Assuming my block has not changed in 4 months (I know it could have but bear with me) if simply dropping my lower atrial rate to 40bpm(from 60) and increasing my PR interval to 500ms (from 400ms),  these two changes have actually increased by Vpacing% from 47% to 80%. This an increase of 33% which in time is about 8 hours of the day which is about the time I spend in bed.

There might be a heart rate that once I go above there is no block - is that possible? It is obviously not 60 but it could be not much higher?

As for how I feel one day I did feel a little light headed when standing for a portion of that day. I also feel like exercise is harder than it has ever felt. How can that be? My heart has not changed just the signal?



Some tuning required

by crustyg - 2021-02-25 13:02:11

I'm 100% with you about %V-paced - if we're talking about an apical-RV lead.  There is nothing wrong with an RV lead that connects to the His-bundle, and, we hope, RV-interventricular septum placing may prove as effective at preventing the harmful effects of LV remodelling associated with long-term RV-apical pacing.  I can't recall if you've shared your RV lead placement?

OK, HB.  There is a rate *below* which you may not see much/any HB. But, even if you get your PM tweaked so that it doesn't pace your RV lead when in that situation, you aren't going to want to live your life at that HR.  Make sense?

You are correct, that beats that are V-driven will usually be less effective at delivering blood flow to the aorta - A/V dys-synchrony.  AgentX86 quotes a 20% improvement in cardiac output from restoring A/V sync, and I can attest that whatever the actual measured amount, it made a *big* difference to me.  A 20% improvement sounds about right.  So, for you, if you can find a way to have most of your heartbeats A=>V you will get better cardiac output for each beat.

I suspect that the most important thing for you is getting your PM tweaked to try and exploit your AV-conduction, whilst coping with your long P-R interval (==slow AV-conduction).

In your shoes I would be pushing to have a session with EP-doc, EP-tech, +/- company rep to get my PM tuned as perfectly as possible.  If this can be done where they have proper resuscitation facilities, then almost any adjustment is possible as they try and optimise your PM settings without worrying about triggering a nasty arrhythmia.


by islandgirl - 2021-02-25 23:05:56

I used to be paced 99+% in the atrium (sick sinus syndrome) and ~5% in the ventricle.  With my last optimization, I am now paced 99.9% in atrium and 99.8% in ventricle.  I discussed this with the EP and he told me that I need not be concerned about the % of pacing but the synchony of the heart.  I have an optimization about every 6 months, when the EP sees indications on the ECG.  It usually takes about an hour with my EP working with the device computer and coordinating with the ultrasound tech.  I know my heart function has decreased.  The last time they did the optimizaiton, it wasn't perfect, but they got it to the best they could.  Good luck.  

Thank you

by quikjraw - 2021-02-26 06:17:28

Thank you both.

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It may be the first time we've felt a normal heart rhythm in a long time, so of course it seems too fast and too strong.