Recent change in heart rate after extended period with bradycardia

Early in 2023 my resting heart rate abruptly dropped to about 40 bpm (often falling to the mid/upper 30s overnight and sometimes during the day).  I’m currently 63, and for most of my adult life, I’ve had a resting rate in the low to mid 50s, as I’ve been a runner and cyclist since my teen years.

I was diagnosed with sinus node dysfunction, and along with bradycardia, I experienced chronotropic incompetence (heart rate wouldn’t go above 120 during vigorous exercise).  My local cardiology office and the electrophysiologist I was referred to recommended a pacemaker.  I did a fair amount of research (including helpful posts from the site here!) about rate response and preferred pacemakers for cyclists, as my EP was partial to Medtronic pacemakers but came around to the idea of using a Boston Scientific given the importance of cycling in my life.  Despite the low heart rate, I was mostly asymptomatic and put off the pacemaker implant, due to lack of symptoms, along with other things going on in my life.  My plan was to go ahead with the pacemaker early this spring.

This February, however, my heart rate suddenly changed, with my resting heart rate in the 70s, quickly ramping up to about 200 with moderate exercise, including walking flights of stairs (combined with some shortness of breath and heart palpitations).  A 48-hr. holter monitor showed paroxysmal AFib (4.5%).  In the past five years, I’ve twice had bouts of persistent AF, treated by cardioversion (the last one was about two years ago), but cardioversion isn’t an option for paroxysmal AF.

My EP wants me to go ahead with the pacemaker implant, given the likelihood that the bradycardia will return and its resulting limitation on options for treating the AF.  He has put me on Amiodarone (200 mg/day) on a short-term basis, and this has had a moderating effect on the arrythmia.  While my heart rate still spikes with moderate exercise, it doesn’t go above the low 160s, and I don’t feel the shortness of breath or any palpitations.

Has anyone here experienced an abrupt increase in resting heart rate after an extended period of bradycardia or had to deal with the combination of paroxysmal AFib and bradycardia?  While it feels counterintuitive to have the pacemaker implant after a period of nearly five months without a low heart rate, the prior sinus node dysfunction diagnosis would seemingly indicate that the bradycardia could return suddenly, just as when it originally began in 2023, which could be a real danger if I were taking rate lowering medication for the AF.

Thanks for any feedback or advice!

Todd

4 Comments

Sounds all too familiar

by Gemita - 2024-07-01 03:07:49

Todd, you are describing the symptoms of tachycardia/bradycardia syndrome so well (also known as sinus node dysfunction).   I also have paroxysmal AF and many other arrhythmias so I know what you are experiencing.  All treatments are possible for paroxysmal AF, even cardioversion, should a fast AF episode occur and be difficult for the patient to tolerate.   

My Cardiologist/Electrophysiologist recommended a dual chamber pacemaker for me in 2018, so that he could “safely” give me rate lowering medication (anti arrhythmic meds - Flecainide, Digoxin and beta blocker - Bisoprolol) without fear of these meds dropping my heart rate to dangerously low levels while treating my paroxysmal (intermittent) AF which used to occur at rapid ventricular response rates.  My minimum pacemaker setting is 70 bpm and this higher minimum rate certainly helps with my mainly bradycardia induced arrhythmias.   

I am glad Amiodarone is working for you.  It is an effective anti arrhythmic med, one of the most effective, but it comes with some potentially serious side effects and needs to be carefully monitored with regular blood checks.  Rate control meds like beta blockers or calcium channel blockers are usually safer I was told than an anti arrhythmic med.  Have they considered an ablation for your AF?

Certainly by going ahead with a pacemaker, your doctor will be safely able to treat any high heart rates with medication, without fear of triggering worsening bradycardia.   When sinus node dysfunction starts it is usually progressive so if you trust your doctors, I would be inclined to go ahead with pacemaker surgery since there would appear to be a need.   Not sure how to advise you on best manufacturer model for your activities. This needs to be discussed with your team or a rep from their device manufacturer.   Good luck

Pacemaker

by piglet22 - 2024-07-01 05:20:32

Yes, it's a common route as your condition can deteriorate to the point where a pacemaker becomes the best way forward.

With better control of your condition you can take medication like beta blockers - Bisoprolol is popular - without too much in the way of side effects.

There are a few athletes in the club who carry on with their exercise as though the device isn't their.

I certainly was able to do 18 years of cycling without ill effects and with the PM BB combination.

Press on with the PM as soon as you can

by crustyg - 2024-07-01 06:52:35

There's some evidence (I may have the paper somewhere) that vigorous RA pacing for athletes with SSS+CI *reduces* the chance of AFib.  The logic is that with very low pacing impulses from the failing SA-node, clumps in the RA fire off anyway, leading to AF.  Providing a more normal rate of simulated SA-node pacing may prevent this.

I'm a keen cyclist, implanted for 5years, and my EP-doc and I have a bet about whether/when I will end up in AFib.  So far, I'm ahead, perhaps due to vigorous Rate Response settings on my Boston-Sci Accolade.

I'd avoid beta-blockers for as long as possible, given their side-effect profile.

Best wishes.

Tachy-brady, etc.

by VT Wombat - 2024-07-01 12:38:18

Hi all, thanks for your responses!

Gemita - my understanding was that tachycardia-bradycardia syndrome typically involved more rapid alternating between bradycardia and AF or other SVT arrythmias (whereas I've experienced a year of bradycardia with no AF, then 4+ months of paroxysmal AF with no bradycardia).  Regardless of whether my interpretation was correct, it is clearly the case that sinus node dysfunction and AF are strongly correlated, though the exact causal relationship and underlying mechanism aren't yet fully understood, and the likelihood is that I'll be dealing with both for the long term.

I have an appointment with my EP tomorrow and have tenatively scheduled a pacemaker implant for July 11.  The EP previously said we'd discontinue the Amiodarone after the implant, which I'm happy about (no side effects thus far, but I spend a little too much time at Google University and have read about the many long term side effects!).  I expect he'll switch me to rate lowering meds (likely diltiazem, which I took prior to my first cardioversion, as I had problems tolerating beta blockers) and will discuss the possibility of an ablation.

Thanks for the moral support!  I've mostly come to terms with the idea that a pacemaker was likely an inevitability, but it's certainly not abnormal to nonetheless have reservations about it and want to be sure that the diagnosis is correct and the proper plan is in place.

Todd

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