Rate Response/Beta Blocker

Background: Had a Medtronic Azure implanted in October with a lower rate of 50 bpm and upper track of 160 bpm. Rate response has been turned off. I'm an endurance runner (I do a few trail ultras a year and have two road marathons planned in 2023) and also do CrossFit a few times a week. The pacemaker was implanted for bradycardia/sick sinus syndrome/marked first degree AV block and a suspected exercise-induced left bundle branch block. There were a lot of AVNRT episodes captured on a Holter monitor prior to implant and there continue to be a lot since implant.

I'm back to running and doing CrossFit, though both are definitely at reduced effort. If I get on an exercise bike at CrossFit, it's awful. I feel like I have no oomph. Ditto a ski machine. I'm easing back into weightlifting and that seems to be going okay.

On runs, I can go long and slow and have plenty of endurance, but I feel draggy for the first couple of miles. I feel MUCH better after the first mile or two. If I get going too fast, especially in the later stages of long runs, OR if I do a double workout (two workouts in one day), the HR jacks up too high. The EP says once it gets over 180, I should assume I'm experiencing an arrhythmia and back off. Fortunately it does come down again when I slow down or stop running.

The EP and I talked it over. To address the oomph problem, we're going to try turning rate response on. At the same time, to lower the number of arrhythmia episodes, we're going to try a beta blocker (slow release propranolol 60mg.) Has anyone who's an avid exerciser tried this? What was your experience like? Suggestions on things to look out for as I experiment with this? I go in to the lab tomorrow to adjust the rate response. Haven't started the beta blocker yet.


Beta Blockers

by Gemita - 2022-12-28 18:38:47

Mtn Grl. We have a few things in common:  arrhythmias, Sick Sinus Syndrome and the need for a beta blocker.  I take Bisoprolol which is a cardio selective beta blocker (mainly targets the heart at low doses) unlike Propranolol which is a non selective beta blocker, so affects the heart, lungs and other organs, so potentially could cause more side effects although I see your dose is very low and slow release.  

I have to admit that a beta blocker can really slow me down, which is what they do, so exercising to full capacity while taking a beta blocker may be difficult to achieve.  My best advice is to start on the lowest dose possible and gradually build up if needed and not to push too hard with exercise until you get the balance of arrhythmia control/exercise/beta blocker dosage right for you.

You may get symptoms initially from your beta blocker like increased fatigue but side effects should ease as you get used to the medication.  As a matter of fact I had to have my Rate Response turned off in October because I had an increase in arrhythmias with it turned on and I will need to work with my technicians to get this sorted.  I hope you do better.  Be patient because it takes time to get Rate Response adjusted to suit each one of us.  I wish you lots of luck tomorrow and in the future

it's a challenge but it can work

by Tracey_E - 2022-12-29 10:08:52

10 years of CF, 5x a week with extra runs before class 3 days plus long run on Saturday. I switched to OT last year because my joints hate me but I'm still running. I've been on and off a beta blocker several times. 

It sounds like you have a responsive and supportive doctor. That's half the battle.

The beta blocker is going to hold your rate down when it wants to race, but unfortunately it's also going to hold your rate down when you work out. It took me about 6 weeks to adjust. That six weeks felt like slogging through the mud but then one day my legs felt good again. I found it helped taking it at bedtime. Experiment with time of day and when you work out, ask your doctor for recommendation.

Rate response will help you get your rate up when you work out. Mine was initially off but turned on later, like you. There are different settings and it took a few tries to get it right. I got on a treadmill and they adjusted the settings that way. That saves a lot of trial and error.

I ended up with fairly aggressive settings so my rate goes up very easily. This is great at the gym. It was just now annoying when I had a client on the phone and walked upstairs to get to the computer, was huffing and puffing for a minute. I'll take it if it means easier workouts, but it can be annoying at times when my rate goes up so easily. 

Caveat, it's not going to be much help on the bike because it's based on motion, and our torso doesn't move much on the bike. You might have better luck running or on the rower. Definitely avoid the bike until you adjust to the beta blockers because they're going to suppress your natural increase in rate and the rate response won't pick it up to compensate. 

When you do doubles, are you super overly diligent about hydration and electrolytes? I don't know if it's just my physiology or my heart/meds, but what is enough for most people is not enough for me. Low electrolytes can cause arrhythmias.

Good luck! If it doesn't feel right, don't be shy about going back. And be patient with the beta blocker, expect it to be a hindrance the first few weeks so back off on the workouts a bit until you adjust. 

Exercise experiments

by Mtn Grl - 2022-12-29 12:29:31

Thank you, Gemita and Tracey_E. This is all very helpful information. I suspect that every run and every trip to CrossFit in the coming weeks will be an experiment. It's hard for me to tell when I'm tired or struggling with a workout because I'm having a day that'd make anyone tired, or if it's due to my heart and/or the pacemaker and its settings. A lot of communication with my running coach has been me saying, "I feel so slow, but I don't know why." Training by heart rate zones is a challenge when I'm still figuring those out. Ditto figuring out recovery based on resting heart rate, since mine is where I'm paced rather than going up or down as an indicator of how well-rested I am as it is with other athletes.

I'm pretty diligent about nutrition and hydration, especially when I'm on long runs/doing doubles. The fatigue has me craving sugar and caffeine more than usual when I'm not exercising, but I'm consciously reining that in to focus on protein and good quality carbs in my everyday diet. I suspect I'll need to dial that in even more.

It'll be interesting to see how the rate response changes things. The tech told me she set it to 3 out of 4, with 4 being the most aggressive setting. I figure I'll wait a week or two to start the beta blocker so I see the difference in having the rate response turned on before adding a second variable to the grand experiment. Good to know that the beta blocker will take a few weeks of adjustment before I'll really know how it's working. The EP urged me to take it just before bed to help ease side effects.

The tech gave me a card with the lab number and emphasized that I should call with questions. I always hesitate to bother them with something that may be trivial, so it was a good reminder.

Thanks again for the feedback. There aren't a lot of pacemaker patients who engage in this level of activity, so resources are tough to find!

heart rate zones

by Tracey_E - 2022-12-29 14:01:38

Whatever your zones were in the past are all going to be different now. That's hard for a lot of athletes to swallow because we love our targets. Discuss with your coach and doctor, but I would suggest ignore them for the short term and instead go by how you feel. Take note of where your rate is when you can talk but not sing, where it is when you go all out, how fast it falls. If it's up due to rate response, it will fall fairly quickly when you stop. Re-evaluate target zones in a couple of months once your settings are fine tuned and you've adapted to the meds. 

It's not surprising you're still more tired than before. It's a minor surgery but it's still a shock to the body and 2 months isn't really that long to get back where you were. You're just now starting to work on fine tuning the settings. Sometimes we have to be patient and let our body heal, listen to it until we figure out our new normal. I know I get cranky and impatient when I have to back off or slow down. I'm currently babying a bulging achilles tendon, had to defer a race two weeks ago and the half in Feb isn't looking good, so I do get it. Being patient sucks. But not being patient doesn't pay off, it just causes more trouble down the road. 

There is a Facebook page called Cardiac Athletes that you might find helpful in addition to here. Lots of super active people there with all sorts of conditions to deal with. Not all are paced but there are always a lot of responses to pacing questions, and lots of high level athletes that understand where you are mentally. 

Don't hesitate to call the number, even if it's minor! You aren't bothering them. I've found that when you find someone responsive and helpful, that they actually enjoy the challenge of getting us back to full activity.  Couch potatoes are easy, we make them work for it lol. 


One thing at a time

by Persephone - 2022-12-29 15:19:25

Maybe consider one adjustment at a time. I can only comment on my personal experience - at my one-year-out stress test (I had complaints about not being able to fully resume normal activities) the clinic interpreted my results as tachy-brady and wanted to immediately start a beta blocker. We talked more about rate response and it was agreed to turn it on that day, and I would go home with a monitor but no meds. All went well with the RR only - no tachy episodes on the monitor.


by Mtn Grl - 2022-12-29 17:42:39

Good to know you were doing one thing at a time, Persephone, and that it worked well. That's my plan with holding off a little while on starting the beta blocker. I'd like to see how I do with just the rate response so I can gauge what it does first. Today's run felt very strange. I was loopy for a lot of it. Not dizzy or in any way unsafe, but my head felt odd. The adjustment will take time.

Good luck with the Achilles, Tracey_E. Those are always time-consuming injuries to heal. Fingers crossed for February!

On training by HR zones, that's always been a challenge for me because I never fit a normal range. So going by feel (and, like you say, the talk test) is where we are. I'm hopeful that things will settle down so I can eventually get to a new normal. Thank you for the mention of Cardiac Athletes. I'm going to search that now. It sounds like a great resource.

steve triathlete

by stevebne - 2022-12-30 02:14:27

I agree. The PM is a 'fix' for your heart disease but does not return you to normal! I have found that essentially any Garmin algorhythm that is based on HR is now useless. And that includes HR based zones. I now exclusively use pace for swimming and running, with power for cycling. If you are using training peaks this is an easy changeover. 

When running and cycling, my HR soon moves to my fixed maximum of 150 and stays there. So my Garmin and TP graphs show a flat red line at 150 for almost the whole session. This means that HRV during the session is almost zero and so you get a weird score of -16 for performance indicator. This also means that all the VO2 max metrics are wrong. 

It was strange when I first started on the 150 HR but as I don't think about HR at all in training or races it isn'e a concern. 

Note that I have Garmin set to alarm if my HR gets > 160 as this would be an arrythmia for me and that is a whole different problem.

PS: I checked all this with my cardiologist and the BS tech and everyone seems happy. I also did an exercise test (interval running for 45 mins) and then my appointment to review the results: yep, 150 flat line! And once again, no-one was concerned.

HR zones

by Mtn Grl - 2022-12-30 15:09:02

Oh, yeah, HR zones have definitely been useless for me! I don't get the flat line you do, stevebne, but effort and HR are way out of whack from each other. I go solely based on RPE these days, and have been since before the pacemaker. Trying to use Training Peaks with HR wasn't working. I have a running coach who's good with that. We touch base after every workout to monitor both daily fatigue/performance and trends and adjust accordingly. I'm the coach's only paced athlete so it's a learning curve for both of us.

HR zones and training with Azure Surescan XT MRI

by Bird - 2023-01-15 10:35:36

I took me 6 weeks and 5 setting changes to adjust the Azure PM to let me train somewhat close to pre PM training.   (cycling.. 7,000mi/yr.. weights/hiking).   The key was working directly with the Medtroinic Field Rep who monitored me while I went riding outdooors doing hill repeats simulating riding here in the mountains of Western NC.

Net net Rate Response off, Daily lower limit 50, Daily upper 175. 

We tried differnet settings after I complained that my HR would not go up to zone 4, so the office tech turned RR on set to 145 then tried 165, but we found out that hitting gravel/single track or bad pavement would peg my HR to the setting and stay there...(ie  RR on upper limit 165.  I hit gravel and my HR stayed at 165 for the entire time [55mins] not good when your HR max is 170.  When it was set to 145 it was like a crit race pace but I could tolerate it, however it would not let my HR go higher.).

It takes me longer to warm up before I feel OK to go  usually 20-30mins.  I am being paced a lot ... Ventricle 97%, Atrial 53%, and I have frequent PAC's.  Back to 2+hr rides and doing HIt intervals on the smart trainer. I will be upping distance/time over the next 3 months so it will be a learning/adjusting/expectation process.  




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