Update on new pacemaker settings

I have 2nd Degree AV heart block.

It has been a week since I have moved from minimal pacing (13%) set at VVI40 (my ventricles will not beat any less than 40bpm) to DDD 100% pacing.

My heart thuds stopped immediately. The long wait before pacing (1.5 seconds on blocked beats) is now gone. So that is really good.

I feel a little less fatigued but not a step change so let's see how that progresses.

Exercise is more complicated. I have now done three runs at these new settings. When I ran hard on VVI40 settings I would get to to 180ish bpm but almost certainly would have ben skipping beats. Running was much harder and I am about 20% slower than normal (normal being before bmy heart block started in 2020)

the three runs on DDD and full pacing are definitely showing that my heart rate is not reaching 180bpm on these harder runs. I have got to about 150ish.

I find this fascinating. I do not have any issues with my natural pacemaker yet only a few days after this setting my heart rate does not seem to need to climb to 180bpm for the same efforts.

This has got me pondering, has my high heart rate in the past been compensating for my heart block and I just did not know it?

In other words beats were being missed so my heart rate increased to meet the demand. if so I am expecting that once these new settings have bedded in I may notice my heart does not need to work as hard for the same effort.

Any thoughts on my logic?


4 Comments

It sounds as though you needed that mode change

by Gemita - 2023-10-03 02:13:54

John, 

Thank you so much for the update.  I hope you got some of your questions answered and that you are happy with the results of your settings changes so far.  I am so pleased the thuds and long pauses have been eliminated.  Was your relief instantly felt?  I hope this setting change will allow you to achieve so much more during your activities and help you to sleep better at night too. 

You mention when you ran on the VVI 40 bpm setting you would get to around 180 bpm and notice skipped beats.  Running seemed much harder you say.  Although the odd skipped beat is often said to be benign, if they are prolonged and frequent, they can cause a deterioration in the heart’s pumping function very rapidly.

From your comments with 100% DDD pacing support your heart is clearly no longer struggling and that can only be a good sign that this setting is more appropriate for you John.

I think your logic is correct, in the presence of skipped beats from electrical disturbances like heart block, the heart has to work harder to compensate and to maintain adequate blood flow.  Perhaps your higher heart rates in the past were a sign of your autonomic nervous system kicking in to provide support as your disturbances worsened?  Now that your heart is adequately supported, pacing in DDD mode at 100%, you are noticing less effort is required to reach your goals during exercise?  

Finally, you ask whether your higher heart rate in the past could have been due to compensating for your heart block and you just didn’t know it at the time?  I think I know what you mean.  I appreciate not the same condition, but I recall with Sick Sinus Syndrome when my heart rates started to fall suddenly due to electrical disturbances, my heart rate and blood pressure would often become noticeably “volatile” going from one extreme to another.   It felt like a protective mechanism to help "reset" my heart rate and to bring it back up.  

I am expecting too that once these new settings have bedded in you will notice that your heart will not need to work as hard for the same effort.  I hope you can now relax and move forward with confidence John that your heart is being "adequately" supported? 

makes sense to me

by Tracey_E - 2023-10-03 11:26:22

I'm no doctor, but that certainly makes sense. When we are in block, our heart works extra hard because the atria doesn't know that the ventricles aren't keeping up. It just thinks it has to work harder and harder. 

second degree Heart block problems and settings

by Selwyn - 2023-10-04 05:50:14

 VVI ( that is ventricular paced, ventricular sensed and inhibition of anything else)  means you are relying solely on your SA node ( physiological pacemaker) to conduct a sensed impulse from the atrium to the ventricle. It would seem that perhaps your own SA node is not quite as good as the timing cycles of DDD mode ( dual pacing, and sensing, dual response ). 

The thuds you experience are likely to be atrial sensed ventricular paced beats whilst your atria are doing their own thing. There is then some mistiming  with the relationship between atria and ventricles which has been corrected by DDD pacing ( where there is sensing of both atrial and ventricles and pacing of both of these chambers, with sufficient blanking ie periods of electrical  insulation safeguards to stop mistiming). The blanking periods are there for this reason, the downside of this is that when you increase your heart rate, there is an upper limit, that relates to the blanking. Hence you cannot raise your heart rate on exercise as high as before. 

Of course, these parameters are adjustable ( I had mine shortened  to give me more heart rate) However, a reduction in blanking time, may well increase your upper rate limit and put you at risk of mistiming and as you raise your heart rate to a fast beat you can get electicity flowing backwards to the sensors ( so called cross talk that can result in terrible problems of a very fast circular electrical current and heart beats out of control).

I hope this answers your queries. It is better to have proper coordination between the atria and ventricles in the long run of life than to have a fantastic upper rate limit.

I will keep you updated

by quikjraw - 2023-10-04 06:12:11

Thanks for your thoughts both.

I will definitely keep you updated on how this progresses for exercise. it is already a bonus that the heart thumping has gone if I can run more easily then I will be over-the-moon!

EDIT

Selwyn your post came in as I had posted. Thanks for that detail. I will read it again to try and get that clear in my head :)

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