The better in shape, the more PM I need?

Hi,
I am a 33yr old active male with a PM since 1 year, due to dizziness attacks caused by AV Block III. I have it only kick in with a heartbeat lower than 45. Other than that I am healthy.

I am planning to train for a marathon and was wondering:

Usually if one is getting in better shape, the resting heart rate goes down. For instance a healthy amateur marathon runner can have resting heartrates of 40 easily. So does that mean that my heartrate will go down too and I will use my PM more then? So in this case, the PM would be working against me?

Or once I am in better shape, should I ask my doc to adjust the pm to kick in at a lower heart rate?

Not sure if I am getting my point across. Any help here by other athletes would be appreciated.

thanks,
dave

4 Comments

PM Settings

by SMITTY - 2011-09-19 10:09:27

Hey Dave,

I think I understand what you are asking. I also think you are trying to add apples and oranges here.

Third-degree AV Block is a medical condition in which the impulse generated by the heart's natural pacemaker is unable to travel to the ventricles. The inability for the that impulse to get to ventricle can happen at any heart rate. Just because excellent physical condition gives you a resting heart rate below the low set point on your pacemaker does not necessarily mean the heart block will no longer rear its ugly head. When it does the pacemaker has to step in to keep your heart pumping blood.

But I'm not a doctor so for an answer you can rely on, you need do need to see your Dr and let him explain your pacemaker settings and the reasons for them.

Good luck,

Smitty

yes and no

by Tracey_E - 2011-09-19 12:09:10

With av block, the atria and ventricles have an electrical disconnect so the pm is simply completing the broken circuit. The SA node in your atria works perfectly normally and is setting your hr, the signal is blocked on the way to the ventricles. Any time the atria beats, the pm will pace the ventricle if it doesn't beat on its own. So, ventricular pacing doesn't have a lower limit because it's following a lead, not setting the pace.

The lower limit of 45 is atrial pacing. With av block, we almost never pace atrial because we don't have an atrial problem. If your atrial rate would happen to drop too low, then it would kick in and pace atrial to bring you up to 45. It's unlikely with any amount of training that your atrial rate/natural resting rate will drop below 45. Yes, some athletes have very low rates but they also have hearts with normal electrical systems.

Typically when we have a block, the atrial rate is faster than it should be. I've never heard a medical explanation but it's common and here's what I think happens... in a normal heart, the SA node monitors the oxygen level in the blood, when the oxygen drops the atria sends the signal to the ventricles to beat faster. With an untreated block, the SA node is sending out these signals to beat faster but nothing happens, the ventricles are still slogging along at their lazy, random pace because they never got the memo. So, the oxygen level is still low and the SA node is probably thinking it needs to go even faster and this is why I think we just end up with a faster resting hr. I do at least an hour of high impact exercise 5 days a week, my resting rate has never changed.

Sorry to be long winded! My point is, exercise and do what you want to do. If per chance your hr drops below 45 and you think it should be lower, talk to your dr. It's unlikely they'll take it any lower than that (normal low setting is 60 so you're already very low) but it can't hurt to ask. Lower limit isn't really your issue with av block, however, keeping your rate up when you exercise is why you have the pm. The pm will never work against you, your own heart is setting the pace only now your pulse is finally at the pace it should be because that broken circuit is fixed.

Thanks!

by talldave - 2011-09-20 03:09:03

Thanks! Great answers!

Exercise Rate

by jkatcl - 2011-09-26 07:09:48

Great info. My setting is:50 and 140. When i exercise i wonder if my pulse goes to 140 or above what happens? I get it up to high 130's Thanks
Ist time. 2nd degree probably went to a 3rd degree after a afib zap. 76 yrs old. Had pm 3 yrs.
Thanks for any info.

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I am 100% pacemaker dependant and have been all my life. I try not to think about how a little metal box keeps me alive - it would drive me crazy. So I lead a very active life.