Help me understand pacing percentages

Ths is an interesting word problem, so please give me time to set it up.

I recently went to my electrophysiclogist (EP) because I continue to have ventricular tachycardias, sometimes three a day. Luckily my ICD paces me out before it delivers the horse kick. They looked at my intrinsic heart rate and decided the  low  rate of my PM was too high, so they knocked it down from 60bpm to 45. They also dialed down my atrial tracking. My intrinsic resting rate wants to be 48-50. after this change, I never felt better. I had the best nights sleep. It didnt' solve the VT problem. But that's not what this post is about.

On a subsequent visit after it was clear it didn't solve the VT problem, I was anxious to see how much I paced in the upper chamber since they knocked the low rate down to 45bpm. They told me 30%. I was shocked. I had been at 75-80% before the change and that was because the 60 setting never let my intrinsic resting rate take over. With the new setting, I was expecting 0% pacing.  I know my heart rate. We all do if we have pacemakers, right!? I have never broken the 40-bpm yard line. And if I do during sleep, there is no way it could reach 30% of the time because even on my best nights sleep I sleep 6 hours. And 30% of a 24 hour day is 7 hours and change. I questioned my EP.

Well, if i crossed the 45 bpm threshold and was paced, at what rate would my intrinsic HR have taken me if I didn't have the pacer. He said it looks like in the 30s. That's impossible, I told him. Absolutely impossible because I never feel dizzy unless I experiene a VT. I'm as strong as a 16 year old (58 now). Also, I'm testing my pulse all the time in all situations. I track the pulse rate and then I track how quickly it goes back to resting after exercise. Furthermore, I am counting and recording any erratic rates (very few).

How can my HR be in the 30s  or at least below 45 bpm 30 percent of the day and me not know it? I don't even sleep 30% of the day. And that's when he said something I had never heard.

He said the 30 percent is not a percent on the whole day but rather moments during the day. Don't know how to process that but Ok. Good to know. But I NEVER reach the 30bpm either, how do you explain that. He would point to the computer and say it says here.

WRONG.

Here is what is happening, I think.

When I was in hospital's telemetry ward being monitored for a possible PM. My finger never left my pulse and my eyes never left the heart rate monitor. I wanted to know every move my heart made. During calm times my pulse would be at 60 bpm suddenly it would jump down to 30 bpm. That corresponded with a skipped beat that I felt on my wrist. But the pulse went back to 60. The computer recorded a HR of 30bpm, if only momentarily. It didn't raise concerns among nurses on telemetry because they all know hearts skip beats and these computers also show whether it was sustained. In my case it was not.

Fast forward to a tech in a doctors office with a machine. He may or may not have medical experience. But today he represents a company that manufactures pacemakers. He is trained not to give medical advice. But he does give information if asked. How low did my HR go, I ask.  He says, it went into the 30 bpm range. I know that was wrong. My EP said the same thing.

We with pacemakers know our hearts better than even the doctors. Today I am getting a watch that will record my every beat and provide accessible, historical data.

Does anyone have any light to shed on how measurments are communicated. And don't tell me to get over it. I won't. LOL. All the best to everyone.

 

 


6 Comments

pacing

by Tracey_E - 2019-08-14 13:52:09

If you are set at 60 (using that as an example because the math is easier) , the pacer isn't going to sit around and wait to see if you are doing 60 beats in a minute. It's going to make sure you beat once a second. Every time the heart goes a second without a beat, it kicks in with a beat. This is happening 30% of the time for you. 

Don't get too caught up with the monitors, they are not that accurate with us. Pacing tends to throw them off. And watching it all day long will make you crazy. 

If you are feeling good and your icd isn't going off, then you are pacing the right amount. There is no magic number that is considered good or bad.

Wrist monitors not accurate for us either

by Theknotguy - 2019-08-14 14:14:09


Those wrist monitors aren't accurate for us either.  Mine will show me dropping into the 30's when I know the pacemaker is keeping me at 60 BPM.  So wrist monitors are like using the old compass.  It points in the general direction but don't expect to come out to the nearest foot when using them.  
 

Percentages

by Keithwhelpley - 2019-08-14 16:20:54

Thanks for your prompt response. Tracey_E. To be clear then, the percentage is relative to the number of beats your heart puts out and not the time your heart is beating. So a more accurate way of saying it is: one is pacing at 30% of the beats and not 30% of the time? Right? And I’m not sure if there is a difference. 

Thanks for the tip on wristbmonitors. My nurses have always said the most accurate pulse measure is your hand on wrist.

numbers

by Tracey_E - 2019-08-14 20:36:38

I always thought it meant percentage of time, but since we beat all the time wouldn't it be the same thing?  The pacer doesn't count our beats, only when it paces. 

It's always best to count. Second best is a pulse ox that goes on your finger. 

more numbers

by jcb - 2019-08-15 13:53:07

During sleep our heart rate is usually much slower. Not sure why you find it difficult to believe your rate drops below 45, when your normal resting rate is 48-50.

add a number of skipped beats and youŕe pacing 30%.

Also can't imagine you're always feeling the diiference between a rate of 48 and 44.

Monitors are notourios unreliable. A lot of them work with moving averages to compensate for errors, wich means they won' t detect single skipped beats.

 

 

Numbers

by Keithwhelpley - 2019-08-15 16:27:35

JCB,  I get what you’re saying. And I think you’re right. I was thinking that if I was getting that low, I would feel it. But apparently not.  My heart has always functioned at a low rate.  At my last EP visit, we talked about going even Lower and disabling the pacemaker function all together. That made me nervous and pushed my renewed interest in heartbeats  and percentages — wondering if I had anything to fear.

Disabling  the PM arose because I am having repeated VTs, which started three weeks ago for no apparent reason. The EP said he didn’t know why.  He sent me home with anti arrhythmic medicine but I’m still getting 2or 3 VTs a day, which are being paced out by my ICD. both he and my general cardiologist realize I have a functioning pacemaker but I have no diagnosed reason for it. It was put in originally under a misdiagnosis of sick sinus syndrome. It is set to protect me from SSS even though I don’t have it.  When asked if they thought I needed the pacemaker, both said they didn't know.

I think I’m going to have my EP disable the pm and see what happens. Maybe my VTs will stop. 

Thanks all. 

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