Capture Threshold

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by AgentX86 - 2022-10-04 23:41:19

I call it the "elevator test". It's not a threshold test. The (capture) threshold is the voltage where the pacemaker just makes the heart muscle contract or the voltage the pacemaker senses the heartbeat.  This is what the auto-calibration does (understand that you don't have it turned on).

As you note, this test is to find a floor where your heart will take over from the PM.  Yours doesn't, at least above 30bpm.  There is a possibility that there is an escape rhythm under 30bpm but they're not allowed to go lower to find it.

I wouldn't feel like that without my PM.  I'd be dead. My ventricles are completely detached from my atria and I don't even have an atrial lead.  My atria don't do anything at all.

They are looking for our own Intrinsic heart rate

by Gemita - 2022-10-05 00:55:15

They check what our own natural heart rate/rhythm is (called intrinsic heart rate) to see how reliant we are on our pacemaker.  It is important to set the pacemaker to a level at which it can ‘see’ the intrinsic activity of the heart (see first link) which is why they need to do that awful magnet test at each check.

They usually like to encourage as much intrinsic activity as is possible. This ensures more physiological cardiac performance, less drain on the battery life, and may make the individual less pacing dependant. This has to be balanced with the patient’s degree of electrical conduction abnormality and potential chronotropic insufficiency. Encouraging intrinsic activity is usually possible by altering parameters such as the atrioventricular (AV) delay or lower rate limit.  A number of algorithms have dynamic AV delays that aim to maximise intrinsic conduction.

The pacemaker should be able to clearly detect the intrinsic heart rhythm without picking up any additional signals that may occur, so that awful test we all hate will be vital for our technicians to make sure that all our pacemaker parameters are optimised for us individually.  This can change over time, as a result of a change say in our heart condition, medication, or an acute illness which is why they need to continue checking our intrinsic heart rate/rhythm.

Have a look at the following two links for more info on pacing functions.  So to answer your question, that awful magnet check is doing a lot more than just causing a bad feeling.  It is vital in making sure that our pacemaker remains optimised for us personally.

I am getting my pacemaker check today Lavender too.  Train strike over here so travelling into London will be a nightmare so I have to leave early.

https://cdn.ps.emap.com/wp-content/uploads/sites/3/2021/11/211117-Pacemaker-therapy-2-pacing-functions-and-their-role-in-patient-care.pdf

https://heart.bmj.com/content/heartjnl/91/9/1229.full.pdf

Add comments to your medical practice's notes

by Persephone - 2022-10-05 01:24:08

I really appreciated recent remarks made here that said essentially "let them know you are sensitive to this and need warning that it's coming and perhaps time to regroup before whatever other things are involved in the appt" (like rising from a seated position or supine position, for example)

Also

by Lavender - 2022-10-05 10:06:49

Agent-the tech told me it was a threshold test and I was sensitive to the RV part. I don't know why I don't have auto calibration done-the tech just said it's not done. It's quite sobering to know how dependent we are on our devices. Then again-every breath is a gift. In my parents' and grandparents' time-I would be a goner already. 

Gemita-let us know how your interrogation goes today. Thanks for the links. I read both. Very helpful!  

Persephone-yes! Getting that info here and then relaying it to the tech this week caused her to add the note to my pacemaker and also let me know and be supportive to me during the down part of the elevator ride  

Here's the thing-I know I need the device but also am concerned about it making things worse. What choice do I have?  I noticed on my report that the voltage is increased as well as the pace impedance and pace threshold since implantation and even more since the last interrogation. 
 

From Gemita's article:

"However, with increased amounts of ven-
tricular pacing, such as with a patient who
has a complete heart block, further cardio-
vascular complications can occur.
With increased amounts of ventricular
pacing, there is increased risk of condi-
tions such as atrial fibrillation (AF) and a
quicker progression to heart failure"

That is what concerns me. But again, what choice do I have? There's nothing I can do to create intrinsic activity. 

Lavender

by Gemita - 2022-10-05 13:44:18

I feel I haven't helped you at all, only created fear.  That is not what I intended by attaching those links. 

You have a CRT pacemaker so your ventricles are synchronised.  I don't see why you should be concerned about ventricular pacing, unless you were solely paced in the right ventricle (RV) which you are not.  Even then most do not go on to develop Atrial Fibrillation (AF) or heart failure.  So many members here are paced in the RV and have been paced in their RV alone for years and will never go on to develop heart failure.  You seem to have the best pacing system to prevent this in any event.

You appear to be paced in your right atrium (RA) too from your comments, although your RA is still able to function for a good deal of the time without support so you do have intrinsic activity.  You say yourself that your Sinus Node is okay, just disconnected from your ventricles because of your block.  An easy fix with your pacemaker.   That suggests that you have a third lead to the RA too and since you have no atrial arrhythmias, your atrial signals can safely be transmitted to your ventricles.  

How can you make things worse by having a pacemaker?  You are doing the opposite, making things better for yourself by making sure that all atrial signals are getting through your AV block to give you a steady ventricular rate.  Untreated block would be dangerous and cause more symptoms.  

Voltage, impedance and threshold increases since implantation and even more since your last interrogation hopefully will stabilise Lavender.  CRT can be difficult to get adjusted and perhaps the vibration you experienced has adversely affected your voltage/impedance and the adjustments will help.

I will do a separate post on my pacemaker check 

Thanks Gemita

by Lavender - 2022-10-05 16:13:58

I've been a bit upset because there's so little explanation given by doctors etc in my world. The pacemaker tech took more time and actually  printed my report and gave it to me for the first time. It's a learning process and I learn here more than anywhere. Learning allays my fears. 
 

I appreciate you teaching me more about the CRT. I do try and educate myself but the drs give so little time. As usual, I went into my interrogation with about five questions written down. The cardiologist does answer but also is always in a hurry.

I'm more and more comfortable about things but was told this week by the tech at the interrogation that I have no escape rhythm. I had one before. I know my wiring was flickering which led to the device. I know it's permanent and I need it. I guess I was concerned about increasing heart issues.

I am the type who calms more by understanding more. To me-if they know they can't find the escape rhythm by going down to 30bpm-why put me through the experience...I had tears in my eyes from fear. The tech came and hugged me. 
 

Now after what you and agent said-I know they will do this and hopefully the settings will stabilize as you said. 
 

I also had one event-never had one recorded before. It was nonsustained v at 197bpm. It lasted only 14 seconds so they weren't concerned. When I came home, I checked my calendar for the date and time it happened. I realized it was after I had gone up three flights of stairs in a medical office bldg. 🤪 

I wasn't too winded for very long, and thought not much about it. I know my heart was pounding. I'm claustrophobic and don't do elevators. Especially alone. Got stuck for a long time in one. Then again in another location. 
 

I am eternally grateful that I can speak freely here about my concerns, be heard, and get good feedback and support. Whew! I'm relieved!😘

every time

by dwelch - 2022-10-14 02:05:58

I started the pacer journey at 19 years old and for a long time (couple of decades perhaps) got angry at techs that wouldnt warn me.  Perhaps age and wisdom I dont get upset anymore.  

It is always the same experience, they speed you up and slow you down, not necessarily in that order.  For the first time in over 30 years of doing this the last one she asked if I am prone to passing out or falling over.  Currently where I go it is like a normal exam table with a small seating spot and a flat back, not very comfortable, and if you were to get dizzy nothing to hold you up (note I had one doc that they bought recliners so you sat back kicked your legs up, never saw that before or since, had to move a way so stopped seeing that doc).  

I would tell them that you are prone to get dizzy during the test and might fall over so they can be prepared for that.  I doubt they will skip the test, but even if you do not know the names of the test or not or what they do it is the same routine every time.  The test each lead, and then the what if the device turns off.  Which for me, as  tech described quite well, feels like someone is sitting on your chest.  

Even after three decades and even though these tests take seconds, I still feel like my pacer is at the wrong settings after they finished and while I talk to the doc and as long as getting to the car go go home.  But the report showes they put it back, it is likely just mental not physical for me at that point.  

Whether they do this turn it off one then do the jack the rate up one in that order or the other way around it is still a roller coaster, turn me off then jack me up and I start breathing heaver or the other way around jack me up then hit the brakes.

If you get hurt physically during that test, that is on them so warn them, and I would be curious to know how they handle you to keep you safe, physically.

Anyway, we all have that test, and you defiinitely feel it, we may have our own ways to describe it...This is one of those get used to it things, but if you feel like you might actually pass out and fall off the table, tell them before that.  Maybe in a few years after you have been through a few you may or may not feel better/safer about it.