Malfunctioning Pacemaker?

Hello all! I am having issues with my pacemaker that was implanted in December 2019. 

A little background on me: I was diagnosed with a complete (3rd degree) heart block in August of 2016 during a sports physical EKG. I was generally asymptomatic other than a low HR (resting at about 50, max about 120). I am a 21 year old Division I athlete, and had no prior issues completing vigorous workouts such as weightlifting, interval training, and long runs. 

After the pacemaker was implanted, my max HR was set at 170. When I was well enough to resume exercising, I wore a Polar H10 heart rate monitor. During a 1 hour bike ride, I was shocked to see that my HR plummeted from 170 to 115 within 10 seconds. I repeated a workout with an Apple Watch, and got the same results—my HR was consistently plummeting very rapidly during steady state cardio. 

I contacted my cardiologist about this issue and they thought it had to do with the max HR setting. They (supposedly) reset my max to 220 on March 16th. However, I have have HR data from four different workouts after that date all showing that my HR hangs around 170 for 10 minutes, and then plummets to 115 within 10 seconds. I have a strange feeling in my heart when this happens, though it's sometimes hard to distinguish if the pounding sensation is from the plummeting HR or exercising. I am always able to finish the workout, but am becoming increasingly concerned about how quickly my HR is dropping in the middle of workouts. My friend who studies exercise physiology suspects that my pacemaker is "turning off" for some reason, and that my HR is dropping to what it would be if I didn't have a pacemaker.

My doctors office seems to be pretty unconcerned with this issue, though I have yet to find anyone online who has a similar problem. Surely this is not how a pacemaker is supposed to function—does anyone have any ideas or similar issues?


your not alone

by Skeet - 2020-04-08 23:39:56

This has happened to me many times. Techs dont't know the answer and they dont't know how to fix it.My tech did the same as yours and upped my max rate to 170, didn't help. I have discussed this at length with "Crustyg" who has probably already read your post. He knows much more about it than I do. I have a Garmin when riding bike with a Scosche arm band. I think it is very accurate. Riding in Colorado from Durango  to Purgetory I saw my pulse drop from 165 to 110 within 10 seconds. Wish I could give some advise, but wanted you to know others of us have same problen.


It warrants proper investigation at your age

by crustyg - 2020-04-09 04:37:15

As Skeet says, we've discussed this at length elsewhere.  I had something similar happen to me near the very end of a tough ride up the mountain in March - Garmin chest strap (good quality Lead I HR monitor which measure QRS complexes) showed a rapid drop from MaxHR to about 100.  I felt sick and unable to continue and stopped immediately.  After 2min rest I restarted and finished the last 1k. I've had an interrogation since then and fully expected an arrhythmia log event for that date/time, but nothing (although my log wasn't entirely clear from a different ride).  Disappointing, but the point is that my PM (in AAIR) isn't great at recording some events.  Other PMs are the same.

For you, I *suspect* that you're having some form of temporary tachyarrhythmia - perhaps a run of AFlut or perhaps AFib which spontaneously resolves.  It's relatively common in athletes and it's certainly what was happening to me in the years before I dropped into established AFlut.

Solution: get your EP team to implant a reveal device - very good at recording *all* cardiac rhythm events, stays in for 1-3months and then the evidence will be clear.  Yes, a *second* device in your body (no leads in the heart): it's not that uncommon and it will show everyone what's going on.  Your PM is doing what it's been designed/programmed to do which is to not prolong the tachy event (there's a phenomenon called pacemaker-mediated tachycardia which modern PMs are designed to avoid) so it eases back on the pacing => your HR drops like a stone.  I very much doubt that there's anything wrong with your current PM.

Once you and your EP team have reliable data to show what's going on you can work on a plan to fix it: may be drugs to reduce arrhythmias or it may be an ablation, or something else.



by Tracey_E - 2020-04-09 10:38:23

I also have 3rd degree block.  When we fixed the block so the ventricles beat when the atria does,  we found out the atria wasn't always behaving itself. Sounds like yours is doing the same.  It's not the pacemaker malfunctioning, it's just a matter of getting a complete picture of what's going on beyond av block and programming to fix it. 

Turned out I had two different things going on. Sometimes my rate would plummet during exercise for no reason. This was fixed with programming. I think it 's called rate drop response or something similar? My rate can come down gradually but if it drops too quickly the pacer will kick in with atrial pacing to keep it level. 

The other thing that was happening was sometimes my sinus rate would get over what the pacemaker was programmed to let the ventriclese do. So, my sinus rate would get to 180 but my pacer only went to 160 so that's as fast as the ventricles could go. That caused two problems. First, the pacer saw the fast rate, thought I was in afib so started pacing every other beat to make an artificial 2:1 block so my rate would drop in half.  This is great if you're in afib but like hitting a wall if you are working out. I have no history of afib so they turned this off.

Second thing was even when it kept pacing at 160, if the atria is going along at 180 it doesn't feel good. That was as high as that pacer could go so I went on a low dose beta blocker to keep my rate down. When I killed that pacer and got a new one, they gave me one with a higher max, so now my upper limit is 190 and I never get close to it and I went off the beta blockers.

Btw, we figured all of this out on a treadmill. The cardiologist and St Judes rep were both there watching what was going on and making adjustments to the pacer. It took more than one try but eventually they got it so that I can work out without issue. 


I had wondered about that

by crustyg - 2020-04-09 10:48:41

It's a very plausible mechanism Tracey: I'd be surprised if it's the root cause with a max rate of 220bpm - athough Striana1004 puts it in such a way that there's doubt about whether it really has been adjusted that high.  Reasonable enough maxHR at 21years.

Whatever the cause we can agree that this warrants some focussed attention - whether a treadmill session or a reveal device - perhaps both.

Pacer thinking too much

by Skeet - 2020-04-09 13:33:30

I have always thought what Tracy_E posted about pacer thinking it is Afib when it is only exercise related high pulse. When tech tells me I have had episodes on a certain time and date it always coorelates to a hard ride. I have a good nurse tech that works with me now but we haven't really hit on the right adjustments yet.


You know you're wired when...

You have rhythm.

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