Sensed AV Delay

Hi 

Just wondering if anyone might have any idea as to why a 'sensed' AV delay might be programmed longer than a 'paced' AV delay and what effect this might have?  I've always had the reverse programmed e.g. the sensed AVD value is always less than the paced AVD - seems odd! 

Also re: length of AVD. Is 350 msecs a long or average AVD to prevent v.pacing for 1st degree AVB? 

Many thanks 


7 Comments

AV Delay

by Gemita - 2022-12-27 08:25:18

Hi Penguin,

https://www.cardiocases.com/en/pacingdefibrillation/traces/pm/abbott/difference-sensed-av-delay-and-paced-av-delay

https://www.pacemakerclub.com/message/22019/av-delay

350 msec seems rather long so that your heart will be doing all the work.  Might be okay if you have normal AV conduction, but with signs of AV Block, something doesn’t seem quite right.  Have you by chance found the source of your difficult symptoms I wonder Penguin?

Have a glance at a Pacemaker Club link above on definition of AV delay.  golden_snitch gives an excellent definition and also check Cardiocases on difference in sensed AV delay and paced AV delay.

My Medtronic pacemaker AV delay sensed in (ms) is at 150 and paced at 180 but this seems to be a common factory box setting for Medtronic pacemakers, so perhaps not much help.   Hope other members can throw more light?

Thanks for links

by Penguin - 2022-12-27 12:02:23

Thank you for these links Gemita. 

I had read that the PR interval for 'marked' 1st degree AVB is approx 300-350 ms, so 350 ms seems like a pretty aggressive AVD, particularly as the AVD extension element of the AVD can be applied up to 3 times.  

A 370 ms sensed AVD on top of this seems strange having read those links. Can anyone shed any light on why a sensed AVD may be programmed longer than a paced AVD? 

I also have programmed parameters for 2:1 block. This sounds like 2nd degree AV block rather than 1st degree AV block programming. Does anyone know whether this type of programming is used for 1st degree AVB which is defined as 'marked'? 

 

Hi.

by PacedNRunning - 2022-12-27 21:26:43

Usually the sensed delay is shorter than the paced.  Not sure why yours is longer. Could it be they are really trying to minimize pacing? How far apart are they? If your sensed is 350ms. What is your paced? A normal PR is 200ms. If they want to minimize pacing they suggest going no further than 250ms but I've had mine out as far as 350 ms.  So it can vary from Person to person. Just depends on the goal. 2:1 block is just when the pacemaker will track the atrium every other beat. But this should be for higher rates. I hope I answered your question or at least helped. 

AV delay

by Dixie Chick 65 - 2022-12-28 09:18:39

I have Medtronic Azure dual chamber PM and 2:1 AV block. My paced  AV is 280ms and sensed AV is 250 ms. I've had my PM about 2 1/2 yrs. And it's been set the same almost the entire time.

I feel good and this is apparently working well for me, although my ventricle pacing percentage has been increasing, shown in the last 2 transmissions.

Following this thread...

Thank you

by Penguin - 2022-12-28 12:03:29

Hi PacedNRunning & Dixie Chick 65, 

PacedNRunning

Thank you for the info re: the 2:1 block setting.  Is this setting for a specific type of AVB do you know?  I wondered if you could expand on what you said about it being programmed 'at higher rates'?  

I note what you say about the sensed AV delay being set higher as a strategy to limit v.pacing. It seems like a strange way to go about it but plausible.  My paced AVD is 350 ms. and approx 20-30 ms higher than this for the sensed AVD. 

Re: PR Intervals - as I understand them.

Normal - up to max 200-220 ms (age dependent);

1st degree AVB - up to 300 ms.

'Marked 1st degree AVB' - up to 350 ms (with AV conduction beginning to deteriorate). 

'Marked' seems to be where I am, with intermittent dropped beats.  This is why the increase in sensed AVD needs to be explained. Happy to discuss further via private message. 

Dixie Chick

Like you my VP% is creeping up but very slightly (below 5%.) VP was v.high in the past and unlike some fortunate people on this forum, I really struggled with it. Conversely, I tolerated long AVDs pretty well before, but not so well now. 

I'm happy to discuss long AVDs vs an increase in VP with you by PM if you want to send me a private message and if you feel it would help to talk privately.

I'd gather opinions via a range of people if you want to discuss longer AVDs vs higher %VP and obviously talk to your doctors too. Experiences vary quite a lot and research doesn't always reflect what happens in real life.

AVD

by PacedNRunning - 2022-12-28 21:25:09

I see you say you tolerated long AVD's at one point. I will say our electrical system can flip on and off or "short" so if you tolerated it before and no longer tolerate perhaps your experiencing more block. This is EXACTLY what happened to me. We tried to reduce V pacing and it worked for a while. Felt great then suddenly started having block more frequently and didn't feel well. Shortening my delays worked! I don't like pacing so high (100%) when I started in the 35% range. So I understand the less V Pacing. But they may need to shorten it some to relive symptoms. 
 

2:1 is a normal function of PM's it's when the atrium can no longer track faster rates and the device will only see every other p wave causing the HR to cut in half. They just have to raise the HR limit so this doesn't happen. I interestingly enough to a PM due to exercise induced 2:1 block. My HR would suddenly drop from 180 to 90 BPM. 

 

My guess is they have your senses delay so long to allow your heart more chance to work. It will follow A Sensed beats. I'm guessing you only A Pace when resting so that timer will be the 350ms. Could be why so your not waiting to long for a pace d beat. 
 

timinf cycles with pacemakers are very difficult to understand. I had to do a lot of reading and asking questions to understand 

PacedNRunning

by Penguin - 2022-12-29 09:06:34

Hi again, 

Thank you for taking the time to reply and for thinking about these issues so thoroughly for me.  I appreciate it.  A change in device has challenged what I thought I knew about pacing and your thoughts are helpful. The two devices are so very different and I'm having too many problems which appear to have no solution with the new one. 

I'm unsure as to what's going on with AVB and that's probably the crux of the issue. I've had variable info provided and your explanation re: the 2:1 setting has helped.  I'm sorry that I can't really provide you with solid info in return as to what my pacing team may be trying to achieve.  I really need to see the EP. 

Your comments re: 'tolerance' of AV delays and reducing them are interesting. Reducing AVDs hasn't been suggested before, but I'd certainly like my current ones reduced. They're too aggressive.   I'm not sure that I understand how reducing AVDs could reduce v.pacing - seems counterintuitive - but it clearly worked for you. Worth a shot perhaps?

Re: A.pacing - Giving my heart a longer chance to work when resting is a suggestion worth considering as my AP was v.high for years. It's been reduced with the new device by approx 20%, mainly because RR can't be increased as it sets off atrial arrhythmia. RR accounted for a lot of my AP previously.  

Not sure if my AP has reduced any more since the sensed delay was increased above the paced AVD but I'll check. It's certainly a Q. to ask. 

Overall the new device provides less AP, less RR, increased AVDs and undetectable AT / AF. All of the above contributes to frequent PMT.  

The benefits of people like you and a specialist forum like this really come into play when a pandemic causes long waiting lists.  I know that peers can't answer everything and obviously you have limited knowledge of my medical history, but it's really helped to get some suggestions which provide a bit of light in what feels like a very dark place atm. Thank you. 

Its given me some food for thought. 

 

 

 

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