Fountain of all knowledge

Hi Smitty

I have posted this personally as I feel it is too long to go on the forum.

As you appear to be the fountain of all knowledge I thought you may be able to answer some questions for me?

My by polar dual lead Medtronic Sensia was implanted on the 26th November, I am paced 100%. I have been recovering well. Well enough to take myself off to the Caribbean on holiday. My lower limit is set to 60, I have no idea as to the top limit. During the past 10 weeks I have felt like a well tuned sports car, hardly noticing my heart. The only niggly things were 1). I had a 3 ping sensation around the can area every 3 hours, not painful but noticeable if I was sitting still 2). Depending on how I laid in bed I could feel the little electric shocks in my heart.

On my 6 week check I ask the technicians about these and there answers were
1). Your pm is set to carry out a check just once in very 24hrs, during the night and the sensations you are feeling have nothing to do with the pm!!! – Mighty strange as I never had them before, they started immediately upon implantation and were so regular I didn’t need to carry a watch!!
2). It is just a new sensation and you will get used to it.

In fairness I have gotten used to both and although annoying I did not feel strongly enough to argue the point.

So. For 10 weeks everything has been fine, then last Monday my heart began to beat very hard, so hard and fast that fully clothed and with a coat on you could see my heart beating, it also increased from it’s normal rate of 70-80 up to 100.; at the same time I developed spasms in my left pectoral muscle that beat in time with my heart. Not being one to panic or rush to the doctors; and hoping it would settle on it’s own I endured until Friday when reluctantly I made a visit to the PM clinic.
They checked my leads, did a few more checks and then changed my setting from “using my own tissue to complete the circuit, to using the bipolar leads”. Immediately the muscle spasms stopped. They said that this had no bearing on the fast hard beats and that I would have to be prescribed meds by the doctors to decrease the heart rate. However within 20 minutes of the tune up my heart has returned to its normal rate and so after 2 ECG’s to double check the doctors discharged me. On comparing the pacing spike on the ECG’s the pre tune up spike was about ¾” long whereas after it has reduced to 1/16, the doctor said it showed a large reduction in voltage! Coincidently the 3 hourly alarm has disappeared and I tried every position in bed last night and it appears that I can no longer feel the shocks in my heart.(No not sex, but sleeping positions LOL)

My questions are this:

1). What would change so suddenly to cause this drastic change?

2). If they know that using the bodies own tissue to complete the circuit causes such horrible side effects why do they not use the bipolar leads from the outset?

Thanks in advance



by SMITTY - 2008-02-02 05:02:46

Hello Chrissie,

I think the first order of business is to apologize to you for misleading you and others that I have a significant amount of knowledge about pacemakers. I really don’t.

I do have a couple of things going for me that others may not have. I of course have a pacemaker, one that has gave me and untold amount of misery the first several years I had the thing. Because of my problems, after I found this site and learned that many other s had problems with their pacemaker I started to look for any bit of information I could find about pacemakers. Add to that I am old and thanks to heart disease, my physical activity is now limited. For example I can no longer chase pretty girls - on second thought that could be because I’m old and the fact that my pretty little wife would take a dim view of such activity. The result is I get to spend a lot of time at my computer looking for items of interest. When I see a question about pacemakers, if at all possible I’ll start looking for an answer. I end up commenting on many questions here and because of seeing my name so frequently; some think I may actually know something about pacemakers.

I found you questions especially intriguing and I may have an opinion, but not necessarily an answer. Your question “What would change so suddenly to cause this drastic change?” I really have no idea. But we have to remember that our pacemaker is a very complex electronic device, about like our computers. As we have all seen with our computers they do strange things some times for no apparent reason. Of course when something like this happens to our pacemaker it is much more serious, but no less puzzling. If anyone cold answer your question it should be the tech or a manufacturers rep, but fear of liability too often makes them go into their deny mode.

But all is not lost. We have a member that answers to Electric Frank that does know pacemakers from stem to stern. I hope he sees your question and offers his input.

Your next question “If they know that using the bodies own tissue to complete the circuit causes such horrible side effects why do they not use the bipolar leads from the outset?” is also a mystery to me. The following is a short excerpt I took from an article on leads sometime ago that may offer some useable information.

“Leads can be either unipolar or bipolar. Unipolar leads have a single conductor and a single electrode; the unipolar pacing circuit involves the single electrode and the metal housing of the generator. Bipolar leads have two conductors and two electrodes; the pacing circuit is between the two electrodes. Advantages of unipolar leads include decreased diameter and reduced susceptibility to lead fracture. Advantages of bipolar leads include reduced risk of inappropriate sensing of myopotentials, greater resistance to electromagnetic interference (EMI), less likelihood of pectoral muscle stimulation, and better compatibility with implanted defibrillators. At present, bipolar leads are more commonly used, but unipolar leads are still employed on occasion”.

I would say you will have to get an answer here as well from the tech or the rep. From what I see there is no real good reason to use the unipolar mode it you have a bipolar lead. I always check to see which mode my leads are in and should I ever see “unipolar” I’ll be getting explanation poste haste.

As you can see I have spent a lot of time here and answered nothing for you. I will be watching what the others out there that are capable of answering you have to say.

I wish you the best,


Have you been leading me astray

by Wingart - 2008-02-03 10:02:43

Hi Smitty

thanks for that, maybe you haven't given me a definitive answer but it is just nice to discuss things with someone sometimes??

I know from reading previous answers that you have been there and done that and that us youngsters (tee hee) look to our elders for guidance and support, it is just nice to know you are out there.

Not chasing the girls anymore? Who are you kidding, I've seen your photos and I can still see that twinkle in your eye!! Anyway it's OK to look providing you don't touch. LOL.

I also hope Electric Frank or anybody else for that matter can pitch in if they have any further info.

Oh yes, my friend who is an electrician and a bit of a boffin says that it draws more current to use the pipolar rather than the unipolar thus reducing battery life, perhaps that is part of why they use that setting to begin with?? As much as I do not relish the thought of a pm change to quickly it has to be preferable to what I put up with last week.

Take care

Bipolar vs monopolar

by ElectricFrank - 2008-02-04 03:02:46

Smitty covered the whole thing very well so I'll just toss in a quick comment.
The main reason for using unipolar pacing is to work around a bad lead. If one of the conductors on the bipolar lead fractures or if the lead tip isn't making contact with both wires then the only way to make it work is use the body for the return path. The problem is the the same pacing pulse that stimulates the heart to contract will also stimulate other muscles and cause them to twitch. The pacer is usually implanted very near the pectoralis muscle in the check so it will twitch. It usually takes a higher pacing voltage for the unipolar as well and this just makes matters worse.
Apparently your leads are OK as they were able to set it to bipolar so it was probably not set properly at implant.
There is a good reason why unipolar could lead to fast heart rate. It is a bit complex so I won't try to go into it here. I'm glad they were able to confirm it before putting you on unnecessary meds.
By the way if I don't respond to any questions you post let me know via a personal contact. I still haven't figured out how to know there is a response to one of my comments lurking in some area of the forum


by auntiesamm - 2008-02-11 10:02:58

Smitty and ElectricFrank - You 2 guys never cease to amaze me with your research, knowledge and opinions. Thank you for all the times you have answered these questions or given your opinions, and for all the times in the future we will call on you again and again! Bless you both for your dedication to this club. We are all so much better off for knowing you.


You know you're wired when...

You run like the bionic man.

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I had a pacemaker since 2002 and ever since then my life has been a total blessing.