basic question about rate-response pacing

av block and rate response

by Tracey_E - 2020-12-18 21:14:27

If all you have is av block, you will not use rate response. However, it's possible to have both av block and sinus issues. If you haven't used rate response yet, there's no reason to think it should factor into your decision. Even if you were to someday use rate response, it is really only an issue if you are an avid cyclist, swimmer or other sport that the chest doesn't move enough to trigger rate response. For the rest of us, any rate response will do. 

Thanks Tracey

by michaelk - 2020-12-18 21:54:02

Thanks for the fast and clear response. A follow-up question: How does my EP know that there is not a sinus issue in my case? I've done two ECGs, a 48-hour Holter monitor test, and an echocardiogram. In all cases the EP said my heart function was normal, except for the AV block issue. But do you know which one of these in particular shows that the sinus node function is okay (or to reverse it, how do they typically know that sinus node function is not okay)?

And I guess one more follow-up: So if the pacemaker is just following along with the natural sinus node signal, what are the relevant settings/tunings that come into play? I saw other posts of yours talking about maximum rate, so there's that. (I actually don't understand why there needs to be a maximum rate setting, because the PM is just following the sinus node, and the sinus node has a built-in speed control just like in a person who doesn't need a PM, right?) Is another setting the time between the sinus node signal and the ventricle firing (this is the PR period?) or is that just fixed at 200 ms or whatever? Any other relevant settings?

diagnosing

by Tracey_E - 2020-12-18 22:46:40

For me, I was having trouble working out so we did a stress test to see what was going on. It probably would have shown up on a holter. If you are feeling good and nothing showed up on the ecg or holter, and you aren't pacing atrial, it's safe to say you do not have sinus issues. The echo would pick up structural issues and it measures how hard the heart is working (EF).

They can adjust the delay, how long the pacer gives the ventricles to beat before it kicks in. I don't understand the nuances of why they would change that. I believe they might make it a bit longer if the heart sometimes beats on its own to reduce pacing. When we never beat on our own, there's no reason to have a longer delay. That's a guess, I've never questioned why that one is set where it is. 

Maximum rate is how fast the pacer can go, that's a limit from the manufacturer. Many of them go to 180, a few go to 220. Upper limit is how high the ventricular lead is programmed to pace, that's a setting. If it's only set to go to 120 and the atrial rate goes to 150, the pacer will pace the ventricles at 120 and stay there until the sinus rate comes down. The ventricular lead will follow the sinus rate, but only until it gets as fast as it's programmed to go. So, my pacer can go to 220, my upper limit is 190, which is a nice cushion above the 160-170 I stay at when I work out.  Does that make more sense?

Those are the main settings specific to av block.

Thanks

by michaelk - 2020-12-18 23:50:55

So what I'm hearing is that the upper limmit is just a safety limit. Like, a person without a pacemaker could decide theat they want to work out at 160-170, and they have to be careful not to overdo it (although in reality it seems like most people don't have too hard a time knowing when they're overdoing it?). But with the pacemaker you set the limit at 180 or 190, and then it just acts as an automatic safety for you. Does that sound right? And then some people set a lower limit (like 120) not just as a work-out safety but for other reasons?

yes and no

by Tracey_E - 2020-12-19 08:51:21

Yes the upper limit can be set for safety. If your doctor doesn't want you getting your rate over say, 120, then they'll set your upper limit at 120. For some people, working out hard isn't safe for them so they will set it at a lower number whether they're capable of getting their rate higher or not. Some people have a lower upper limit because that's all they need, their rate never goes higher. In my case, a low limit wasn't enough and I kept hitting a wall when I tried to work out. I passed a stress test and my doctor feels I am perfectly safe working out at the higher rate, so he sets my rate to accommodate my needs, so however high I get, my pacer will keep up. 

Thanks

by michaelk - 2020-12-19 13:09:03

I guess I will see what upper limit they set me to, and whether we have to adjust it over time. Back in the before times I was a squash player and I hope to be able to do that again.

Upper limit

by AgentX86 - 2020-12-19 15:01:14

Mine's set at 130 and it's been fine.  I don't to heavy exercise but walk 10mi/day (just got back).  130 is fine for that.  Since I'm in AV dyssynchrony, it takes my ventricals longer to fill so I'm sure that has a bearing on where they keep my max HR, too

Your doctors will surely set your upper limit low until your heart heals and the leads embed themselves.  Then they may adjust it upwards slowly as they see how you progress and your needs.  They're usually quite conservative with this, as noted above, for safety reasons.  It may take some negotiation to get this raised very high.

They can tell by a histogram of your heart rate how much time you're at or near the maximum so can use that as a guide for how much you demand a higher rate.  They're not going to adjust it higher than needed.

Hmm...

by michaelk - 2020-12-19 22:46:31

I don't know what the right pace for me would be (safety issues aside). I'm 53. Using the standard fomula my max is 220 - 53 = 167, and a good but not extreme workout at 80% of that would be about 134. So presumably a setting of 135 or 140 would be okay. I played squash before, but I don't know what my heart rate got to.

I guess with the safety issue I'll just have to wait and see what they say the factors are in my case, and whether they need to limit it for some safety reason I'm not aware of at the moment.

formulas

by Tracey_E - 2020-12-20 09:17:34

Those formulas are sketchy at best, completely irrelevant once we are paced. Your doctor will decide where your upper limit will be to start. It's common to start it low because many are like Agent who never need it higher. Once you are healed, ask what your limits are and how hard you are allowed to push. Have a discussion about squash. Your upper limit will be set to accommodate whatever level of activity your doctor is ok with for you. 

RR is not always needed.

by jds66 - 2020-12-20 20:40:18

I got a new Bi V pacer, third lead to the LBB a week and a half ago. Had a traditional two wire setup for nine years. The V pacing with the two lead setup was going into the 90 percent range, up from the 30 percent range only a few year ago. So, naturally, I was worried about cardiomyopathy, and the Bi V will help that in the long run. 

I had tried Rate Response a few times with my old 2 lead pacer. Each time, in less than a week, told the EP to turn it off, it was a bad thing for me. 

My heart, in spite of Sick Sinus Syndrome, a fairly bad AV node, still does just great when I exercise. I can walk miles and miles, get the heart rate up to 150 or more naturally walking really hard up some hills, and have no issues. 

The EP told me when I got this new device 12-9 to give RR a chance again, since the device was different. 

Same bad results. I know RR has sensitivity settings, but if your heart responds to exercise well, then keep it off, it doesnt help you, in my case, was making my heart over respond to simple things. 

Riding in the car after the surgery was pretty funny, just the bumps of the road were making my heart beat at 120, the accelerometer in the pacer was thinking I was moving. 

Maybe when I am 80 I will need that, but until then, Rate Response, for me, not needed. 

Riding in the car

by AgentX86 - 2020-12-20 22:50:13

That's timely.  Wednesday I went to the device clinic for my semi-annual check (and get my clock changed*).  The night before I was hauling our Christmas tree out of the basement and up a hill to the front door.  I was really panting and feeling it.  I mentioned this to the device tech.  She said she'd make it more sensitive and decrease the ramp timing but that if I didn't like it come back and she'd set them back to my original settings.  Why wouldn't I like it, thinks this dummy.

Driving home was a trip.  I was light headed and it took a minute to sink in.  I remember Tracy_E (I think it was) talking about the same thing some time back.  The motion of my truck was running my PM's rate up.  I decided to give myself a couple of weeks to adjust.  It's been less than a week and these symptoms are mostly gone.  I think it does help on my walks though I'm not sure it's helped climbing stairs.