Pacemaker Unipolar

Hi

My mum is recently operated to fit a unipolar pacemaker. She has been a pacemaker patient for the last 20years. Recently she experienced a continuous thumping in her chest for 4 secs and it never happened after. When examined the doctor says there is a small hair line crack in the wire...but he also says that this is never affect the functioning of the machine. The only disadvantage he states is the lifetime of the machine might be reduced. Can you please advice me on this case? I am not aware of the working system of a unipolar or a bipolar machine.

Thank you
Valli

8 Comments

Uni-bi polar leads

by donr - 2012-07-12 04:07:55

Valli - Currently, most all leads that are used are Bi-polar. (If your Mum got a uni-polar device, that is unusual.) That means that the leads are connected to the "Can," "Box,' whatever you call it with an outside electrical conducting sheath surrounding the main conductor inside. It is just like the lead feeding your TV set - a "Coaxial cable." There may be an insulating cover to the lead, but that is immaterial to the question.

The inside conductor carries the electrical signals from the PM to the heart where they are delivered through the tip of the lead into the muscle. There is a small distance between the tip of the inside conductor & the outside conductor. The electrical signal is conducted from the inside conductor via the heart muscle to the outside conductor where it returns to the PM. The small distance between the two conductors is enough for the signal to stimulate the heart muscle into action.

IN a uni-polar design, like Gellia describes, there is but ONE conductor - the inside one. The return signal uses body tissues & fluids to return the signal to the PM case, which is Titanium, a reasonably decent electrical conductor.

Since the advent of Bi-polar, they have used Uni-polar as a backup (Fail safe) design, so if anything happens to the outer conductor, the body fluids can assume the purpose of getting the return signal back to the PM.

Now, this is a guess on my part. What has happened to your Mum's lead is that the INSULATION has cracked & there is a small leakage current out of the single lead back to her case. This means that if the PM is functioning at all, it takes more energy out of the battery to cover the leakage. It will just wear down the battery faster.

I had that happen to me when one of my leads failed. It was uncomfortable & felt "Funny." I got a new wire when the lead separated completely. Not a big deal - except to the person it's happening to.

Don

leads

by Tracey_E - 2012-07-12 08:07:06

I always get confused the difference between uni and bipolar, so I'll leave that part of the question to someone else. When a lead goes bad, often they can still get it to work. This happened to me, too. They programmed around it and kept it working until the battery died, then we replaced both at the same time. The programming fix often drains the battery faster, which is why the life of the device will likely be shortened. The analogy they gave me was running the air conditioning with the window open. The house will still cool but your power bill will go up.

Hi Valli_m

by Gellia3 - 2012-07-12 08:07:49

My PM wires are unipolar because they are old (32 years now). It is my understanding (and someone can correct me) that a unipolar wire uses the pacemaker body (called the "can") to complete the circuit. In a bipolar wire the electric charge will go down the wire and travel back up a second wire all encased in the insulation. In unipolar, the charge goes down the wire and finds it way back to the PM via anyway it can. Many times the electric charge will hit a nerve and cause the muscles to jerk.

Mine does it all the time. When they check the wires during interrogation they should be able to tell if it's cracked or not. The muscle jerking happens frequently if a bipolar wire gets a crack in it. Much more frequently if the wire is unipolar.

It is possible that your Mom's wire has a small break in it and the dr is right that they can increase the voltage to work around this. This would use up the battery faster and necessitate more frequent battery changes. But, if the wire is unipolar, it may be nothing more than the charge hitting a nerve and affecting the closest muscle.
The 4 sec thumping could also have been the "impedance check" which uses a higher than normal voltage to complete its check. I had to have mine reduced to once daily at 4a.m. because it would make my whole arm jerk violently in a fling four times! Not good if you're holding coffee.

Hope this helps! Good luck to your Mom. I've had a unipolar PM for 37 years now and except for some minor problems that could happen to anyone (wires that scar over or break), I have done well and not missed a thing.

My very best to you both,
Gellia

How soon will it drain the battery?

by valli_m - 2012-07-12 10:07:01

Thank you all for the informative input. With the details provided here, I understand that pacemaker battery will drain due to the current leakage caused by the wire crack.
Is there a panic level leakage? Which case my mum needs an operation soon to fix it. Or can she hold it off as far as it goes?! As of now mum sometimes feels a tingly thumping on the surface yet she can still perform everyday normal activity.
Can you please advice me in this case?

Thank you
Valli

How long is a piece of string?

by donr - 2012-07-13 10:07:13

Valli - that is the question you are asking. It really depends on how bad the leakage is. The PM will tell her Dr. that after a few months in its prediction of battery life. The program that does the predicting is pretty accurate, so give it a month or two for that data to develop.

The REAL issue is what it is doing to her quality of life. If the tingling is not beyond an annoyance, she can wait it out. If OTOH, it becomes bothersome to her functioning, I'd press for a replacement PM.

Also depends on how old your Mum is - if she has been a PM Host for 20+ yrs, she must be in her 70's. If still in good health, why wait & be miserable in daily living? I don't know what your healthcare system will allow/support in these cases.

One thing to take mind of - the crack & leakage will NOT get better, only WORSE with time.

Don

asfasfas

by boxxed - 2012-07-14 05:07:55

There's an easy, common way to tell if you have either an insulation breach or a lead fracture. It applies for most situations (the Riata being a kind of odd-ball).

Techs regularly check the impedance readings of the leads.

If the Impedance of the lead has dropped significantly, below 200 ohms, then it's an insulation breach. (300-1500 are considered normal values.

If the Impedance of the lead has gone up significant, like the programmer saying >3000 ohms or something along those lines, then it's a lead fracture.

Your mother's physician and pacer tech is keeping an eye on this. It sounds like the problem isn't emergent and the doctor isn't feeling compelled to rush her to the hospital. Regardless, they're going to keep a careful eye on impedance trends, trends of capture threshold, and trends of sensing. If it suddenly rises they may re-assess.

Both leads fail at same time...

by donr - 2012-07-17 09:07:12

...not necessarily. I had a lead fail at the 4 yr point - absolutely no reason ever identified. The body internals are a highly unfriendly environment for metals of any type - Titanium is one of the few that can survive in there for any length of time. Stainless steel is another.

Unfortunately. Stainless & Titanium are not especially good for electrical conductors. Those they encase in a polymer. All you need in a polymer is a SUB-MICROSCOPIC leak through an insulating sheath & the interior metal will corrode & fail.

Don

Switch from bipolar to unipolar mode

by Sailor108 - 2012-07-17 12:07:16

asfasfas posted that "If the Impedance of the lead has gone up significant, like the programmer saying >3000 ohms or something along those lines, then it's a lead fracture."

That makes sense especially if it went up fairly suddenly.

Can anybody comment on this case :

The increase in impedance of V-lead took place gradually over a period of 1 year (during the 12th year), while the A-lead of the same age remains constant. Both leads are now 13 years old.

Would a lead (the outer coil) fracture happen so smoothly ? Has anybody heard of fibrous tissue growing over the return ring or any of your doc's spoke about mineralisation or corrosion ? As that would happen gradually.

But then wouldn't it happen to both A and V-leads at the same time ? And did it started after year 12th ?

Thanks for your feeback.

You know you're wired when...

You fondly named your implanted buddy.

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