Who's creating the rate?

So I'm a bit confused about how my rate is being determined. I have a dual chamber PM (Medtronics XT DR MRI SureScan) with leads in my RA and RV. According to my interagation my RA pacing in nearly 100% and my RV pacing is 70%, AP-VP is 70% and AP-VS is 30% with both AS-VP and AS-VS at essentially 0%. So my question is how is my actual rate determined. I know this PM has a Rate Response feature that uses an accelerometer to sense motion and adjust your rate based on that, but I've noticed that my rate is responding to exertion, like going up a hill or progressively liftng heavier weights, which has notihng to do with any kind of motion. My rate during exercise actually appears to be normal for the most part and even during normal activity it's about right. It will also will go up when I get anxiuos, stressed or simply angry, which again has no motion associated to it. All of this is great considering that two weeks ago I couldn't get my rate above 50 no matter what I was doing. So to me it seems like the pacemaker is taking my hearts generated signal and using it to pace me. I have AV block, so I think the pacemaker is taking the signal that's being "blocked" and sending it to where is was suppsoe to go, thus giving me a normal rate. But then I see that my Atrium is "paced" at nearly 100%, which confuses me a since it leads me to believe that the rate resonse (accelerometer) is setting my rate all the time ... this makes no sense based on what I explained above. Any thoughts would be great!


two different issues

by Tracey_E - 2020-05-18 10:01:39

Ventricular pacing for the av block is simply making sure the ventricles beat every time the atria does. It's not setting the pace, it's playing follow the leader.

Atria is a combination of your lower limit that you can't get below and rate response that gets your rate higher when it senses you need it. Sounds like your last adjustments helped? The pacer will always give your heart a chance to beat on its own before it kicks in. If you are pacing atrial 100%, then the pacer is always setting the pace. However, it's possible that you aren't  pacing 100% since the last adjustments so sometimes your sinus node is working. It'll be interesting to see what your next report says. Some people with SSS don't always pace on exertion. They need the pacer to give a jump start then the heart kicks in and keeps going on its own. 

To Tracey

by tapeterson - 2020-05-18 10:52:59

So I think you're excatly right!! As I was typing that post I noticed my beats feeling heavy and noticed that I was at my lower limit and not moving, of which seemed very odd since I was drinking coffee and typing away. Thats exactly how I would feel before the PM ... my rate wouldn't change but my beats would feel heavier. So then after I moved around a bit, it came up off the low limit and has stayed above it. So I think I was in the sick sinus mode with my atria being paced until I "jump started it" by moving.


Oh and after the adustment I still am having two issues that are bothering me. One is that my rate will drop suddenly when I start to exercize, but seems to only do it when I do the stairs. What I think is happening is the MODE is changing to DDDI due to my atrial rate increasing rapidly and posiibly hitting the tacky limit. The mode switch will slow the ventrical rate unitl the atrilal rate drops. So my thought is that when I'm doing the stairs, my rate skyrockets since it's an intense exercise using your biggest muscles, and my PM is thinking I'm going into tachycardia and reacting.  ... at least this is my take on it anyway. All is good with less intense routines ... I creep up to my max rate (130) whicj is way too low, and will cruise there with no issue. The other issue is still the increase on bumpy roads or the latest is from my lawn mower bouncing around. It's obviously not a huge issue, but I really don't like my rate zinging along for no reason.


by Tracey_E - 2020-05-18 15:16:49

If we are active, we are a lot more challenging to fine tune the settings than someone sedentary. Add more than one issue going on, and it gets even more tricky. No two of us are alike so all they can do is an educated guess and see how it goes. They like to make changes in small increments so if it doesn't work, they know what to undo. Sounds like progress, tho.

The   lawn mower and bumpy roads issue is a trade off. I have the same thing. I like my rate response super sensitive so it shoots me right up when I work out. Which is awesome. Rate going up when I walk across the room? Not so much. It's my choice to live with it as it is now. Not struggling to work out is a priority for me so I'll deal with the breathlessness when rr kicks in inappropriately.

If you are hitting your max rate regularly, ask them to turn it up. The max we get to working out should be 10-15 under the upper limit so we have a cushion. I try to stay 150-160 but get to 170 so my upper limit is 190. We figured all that out on a treadmill in the office. 130 is pretty low if you are active. 

Upper limit

by tapeterson - 2020-05-18 15:36:03

Yep the 130 is MUCH too low for me, but they wouldn't change it at that first visit since I was only a week out of surgery. I also had asked to get on a treadmill so they could see the rate drop issue I'm having, but due to thr COVID thing they aren't doing any work on the treadmill. I'm guessin that's because they don't want people breathing hard and potentially spreading germs more so than they would at rest. That's just my take on it anyway. But getting on it when things are clear, is definitly going to be a top priority for me! My next visit isn't until June 10, but I have a feeling that once they see my 24hr monitor results, I'll be getting a call to come in ASAP. I induced that rate drop several times and also included a couple of good steady workouts where I maxed the rate. We shall see !! 


by PacedNRunning - 2020-05-19 03:41:25

With exercise since you pace in the ventricles, they need to calculate your TARP heart rate. This is when your heart rate will drop abruptly and cut in half. If they don't have it set right you can hit that drop before you hit the max track rate. Once you exceed your max track you can have Wenckebach which is dropped beats. So again if they fix your TARP You won't get that either. My Max is 185bpm but I don't hit my TARP rate until 222bpm. Which is never. 

your tachy rate settings shouldn't be kicking in at 130 bpm. That rate should be much higher. So I don't think it's that. See what  They say. 

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