HR is higher than expected during exercise

On-X aortic valve installed on 3 Nov 2017 due to BAV; Pacemaker installed a few days later because of permanent heart block.  I'm naturally paced according to the reports, and I'm trying to determine if the PM is optimized and if there any improvements possible.  I've not had a deep technical discussion with the EP or Boston Sci people, but will in the future.  Next office visit is some months away, though.

Current situation

I've been biking and weightlifting consistently all year, and regained all my strength and stamina. (I have averaged 4 hours of workouts per week since January).   But, I continue to be limited by my max heart rate even at medium intensity outputs - meaning that I cannot push to medium-high intensity levels without getting to 180bpm.  My heart rate is definitely higher now than pre-surgery, when comparing at similar power output levels, perhaps by approximately +30bpm at medium intensity. 

Since I have been pushing hard to get back in good shape, I was expecting that my heart rate at medium or high intensity exercise levels would match pre-surgery levels (or even lower since I now have a functioning AV !).  But it is not the the case, and I'm starting to be concerned about 2 points:

>Is the Pacemaker limiting the heart function somehow?  Is the ventricle being fully actuated with the pacing signal (can you tell that I'm an Engineer?). 

>Am I damaging myself with having my HR at 150-170 for 2 hours a week?


Would appreciate any help / feedback or recommendations on how to approach this with the EP or Boston Sci techs.


Thanks, John



by Tracey_E - 2018-07-30 12:20:58

You've had surgery and are paced now so your rate will be different, at least for a while. Possibly indefinitely. Most of us don't fall into those convenient charts that tell us where our rate should be when we exert. I have congenital heart block so different situation than you, but my rate working out can be anywhere from 120 to 190, same exertion. Yours may settle as you get farther out from surgery. I've been paced 20 years and my rate is still all over the place! If I can talk but not sing, if my legs don't feel like lead, if I'm sweaty and feel strong, I assume my rate's where it needs to be. 

If you are cleared to be working out hard and you feel good doing it, then having your rate that high for 2 hours a week is good for you. Mine gets higher than that for longer than that, my ep encourages it. I do 5 Crossfit classes a week plus 3 runs (2 shorter 2-3 mile after class,  long one of 2-3 hours on Saturday).  The amount of time you spend at a high rate is included in the interrogation report so your doctor knows about it. It also shows up every time you bump your upper limit. 

Are you using rate response? If not, then any high rates are all you and all the pacer is doing is playing follow the leader. The atria beats naturally, the pacer makes sure the ventricles beat a fraction of a second later. They can mess with the delay on how long it gives the heart to beat on its own but that's about it. There isn't a whole lot to optimize there. 

I'm not an engineer so I'm not 100% sure what you mean by the ventricle being fully actuated. A paced beat is not the same as a not paced beat. It's similar and they place leads to get it as close as possible, but it's not exactly the same. 

Is your max 180? My old one was and most of the ones on the market only go up to 180. I hit it often enough working out that I went on a low dose beta blocker for a few years to keep me 150-170. I didn't like taking the meds, but it was frustrating to constantly have to stop my workout because I hit the upper limit, to always be watching my heart rate. The atria is beating on its own so it can go as high as it wants. The ventricles are paced so they can only pace up to the upper limit so it gets to 180 and stays there until the atria comes down again. Not only does it feel awful, but it's not good for us when it is beating out of sync. When mine was replaced, they gave me one that goes to 220. My upper limit is 190 now so it's no longer a problem and I stopped the beta blockers.

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