Sudden drop in HR

Okay, Almost a year ago I got a pacer due to heart naps where my heart would go 'asleep' for up to 10 seconds at a time. This caused at least two syncope episodes where I went down with NO warning and once ended up on the floor and once had my wife sure she was going to need to start CPR (she is a health care professional). After the pacer things were going well but twice in the last month I had cases where in the middle of vigorous exercise I suddenly saw my HR drop from about 150 down to the low one teens. Both times It stayed down for about 15-30 seconds and then started back up. Both times when it happened I felt like crap. Sudden fatigue, light headedness, tingling in the extremities but no chest or other pain just the sudden rate drop. 3-5 minutes later felt fine but a little concerned about what had just happened.

Anyone else experience this? My pacer is for Sick Sinus/Bradycardia/Heart block but up to recently never had a drop in HR when exercising and usually it cratered when I was sleeping or at rest. It is set only to kick in at 50 bpm and has rate response turned off since I often get my HR up to or beyond my theoretical max during hard interval workouts.

Other facts, 51 year old male with no other heart disease except a screwed up electrical system.

Thanks

5 Comments

Doesn't sound like my issue

by COBradyBunch - 2010-06-11 02:06:50

From what you say this should be a trigger that would happen any time you got to or beyond a set HR. If you take a look at my workout stats from this morning:

http://connect.garmin.com/activity/36459906

you will see the drop in question happened at 01:24:00 in the ride. Now my HR would normally be coming down at this point but the thing that was weird, and the graph unfortunately doesn't show, is how rapidly it came down in this case. Also I routinely go into the mid to high 160's on some of my more aggressive workouts and haven't seen this up there and I have even been into the mid 180's once in the past month on a killer hill push.

I did some research and it is possible this could be some sort of a vasovagal response but just seems strange that I had never had them before.

drops

by Tracey_E - 2010-06-11 05:06:42

Regardless of the cause, they should be able to program it to prevent sudden drops. It's called rate drop response, I think, and it can be set to control how fast your rate comes down.

If your atrial rate is higher than your max rate and you are in a block (on your own, not pacer induced), you will not be able to tell by checking your pulse. It would be possible to go to 180 on your own one time but your heart to go into a block on its own the next time you try so your atrial rate is at 180 and your pm is only pacing you to 160 in the ventricle. Very weird that it could happen when it should be coming down, tho. I dunno! Good luck figuring it out and getting a solution.

Hooking you up to the pm computer while on a treadmill might be useful. Push it while they're watching and see what happens on the ekg.

programming

by Tracey_E - 2010-06-11 12:06:09

Something that can happen during a vigorous workout when you have a heart block is your atrial rate gets higher than the pm can pace, the pm thinks you are fibrillating so it puts you in an artificial block which will make your rate suddenly drop. I had this problem. My pm's max was 160, my atrial rate would jump to 180-190 (diagnosed on a treadmill), the pm would only pace me up to 160 which doesn't feel so good (sudden fatigue & dizziness), then as my atrial rate got higher the safety feature would put me in the block and my hr would drop to 80 (half of 160, a 2:1 block) and I'd feel like I was going to pass out. Since I've never been in afib, they turned the feature off so no more sudden drops, and I'm on a beta blocker to keep my atrial rate from getting so high.

Until you figure it out, it's probably best to not push it too much when you work out. If you need a much higher rate than what your heart is going, it's hard on the body. Good luck! This should be a simple programming fix.

Thanks

by COBradyBunch - 2010-06-12 06:06:30

Interesting info... I do use a Heart Rate Monitor for all my exercising and have done so for the last 10 years. Right now I use a Polar for my indoor workouts and a Garmin Forerunner 305 for my cycling and running outdoors (no use using up GPS technology for treadmills, stationary bikes, trainers or elipticals). I am not scheduled to get a pacer check for another 9 months or so even though I am coming up on my one year check. I figured it might be a heart block episode but I didn't drop all the way to 50 like I thought I would had I gone into the issue that gave me the Pacemaker to begin with. Anyway, this has only happened a couple of times and if it happens again I will give my doc a call. The thing that bugs me about it is the sudden wave of fatigue that it brings as well as the lightheadedness. Not that I don't understand the physiology of it, but I hate the fact that it takes a while to recover from it and if it hits in the middle of a big ride it will really suck.

BTW, did a Zone 2-3-4 workout today for 1.5 hours and even with a cold I felt good. But kept myself no higher than 90% TMHR (although my max is higher than than my theo max by at least 12 bpm) and I did keep my effort pretty level with no sudden pushes or recoveries.

Thanks again for the info. At least it gives me something to go on.

Without reading all the responses...

by Pookie - 2010-06-15 10:06:17

just thought I'd mention that my EP told me that not all pacemakers have the rate drop feature.

mine does not have it. i have a Medtronic Enpulse.

Pookie

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