Size of leads??

I'm curious about the actual size of the leads/wires that run down through the vein and into the heart. I was looking at the display of PMs and leads outside the cath lab and those leads look very large in diameter, maybe 1/16" or even slightly larger. I remember seeing one post somewhere on the PMClub that referred to the leads as being about the size of a human hair. That's a lot of difference.

Does anyone know how large these things actually are?




by SMITTY - 2007-12-06 01:12:22

Hi Cathryn,

I know what you are trying to do. You are trying to embarrass me by making me show my ignorance. Well you are succeeding. Why do you think I posted that entire paragraph? It may as well be in Arabic or Chinese for me. Maybe Frank will take pity on us and translate the thing and in the meantime I’ll keep trying to figure out what they are saying.

As for the vein, I have seen the name of the vein used (which I can't recall now) and its location, but I have no idea of its size.

Now to be serious for a minute. You are not embarrassing me just because you asked a question I don't have an answer for and one I have been unable to find. We do have some honest to God medical people that post comments here from time to time, so maybe one of them can answer some your questions.

I'll continue to look for answers because I really enjoy finding answers to the questions I see here. When I post one I hope I'm helping someone and I know I have learned something. And I have to admit, for a dumb old country boy, learning something has always been one of my most enjoyable experiences.

Talk to you later,



by CathrynB - 2007-12-06 01:12:50

HI Ron, I'm no expert at all, but I did ask my EP to show me some electrical leads in his office, and they are much closer to the size of the 1/16th inch you cite than the size of a strand of hair. The lead itself has some sort of insulating sheath (one of you knowledgeable electrical people help me out here please!) around the wire that contributes to its size. I've wondered about this issue before too -- how is it that they can thread several through the same vein over a period of years?

PM Lead Sizes

by SMITTY - 2007-12-06 10:12:44

Hello Ron,

I may have made the comment that a PM lead is about size of a human hair. I said that based on the information I was given during my PM checkup in Sept. I asked about the size of my leads and was told they were about 3 mm OD, which I know is about 1/16". The technician went on to say the wire inside the center of the lead which conducts the current to the heart was about the size of a human hair. I have not seen one of these wires, so I'll not try to argue the point. I see now that I should have looked further.

I don’t know how many of you have seen one of these leads at work, but I’ve had some stent implants and I get to watch the procedure on TV monitor. Those leads flex with every heart beat, whether the PM is actually working or not. Considering that at70 BPM the heart will beat 100,800 times each day, or 36.8 billion times a year, that is one tough little dude.

Below is verbiage from a patent description of a lead.

"An implantable cardiac stimulation lead system for use with an implantable stimulation device includes at least a pair of conductors, braided together and extending between proximal and distal ends and co-extruded with flexible resilient insulation material. Each conductor may be a multi-strand cable composed of MP35N or DFT and have its outer peripheral surfaces coated with insulative material. An electrical connector is coupled to the proximal end of the lead system for connection with a stimulation device and includes terminals electrically connected to the conductors. The proximal connector is thereby electrically coupled to a distal tip electrode and to at least one electrode proximally spaced from the distal tip electrode. The lead system may include an elongated tubular lead body of flexible resilient insulative material having a longitudinally extending lumen for receiving a stylet for aid in implanting the lead system. Alternatively, an introducer sheath may be employed for implantation."

Obviously my info was wrong and I'll be glad to refund everyone’s money that has paid for the bad info.



by CathrynB - 2007-12-06 11:12:29

OK Smitty, since you're "on a roll" with coming up with great answers to all our questions as usual; and since English is my first language, and barely passable Spanish is my second language, and "Electrical-ese" is nowhere among my foreign language capabilities, can you offer a helpful translation of that next to last paragraph? So how big is the vein they stick these electrical leads into? Who on this site has the largest number of leads (active and inactive) threaded into that vein? Just curious. And even after having surgery to re-position my PM so it's deeper (that part is completely comfortable by the way), I still have one tender "bump" up near my PM scar and close to the surface of the skin, and it's got to be part of the electrical leads and hardware, and I'm wondering what it might be? A distal tip electrode perhaps, whatever that is??
Thanks, Cathryn

No way, Smitty!

by CathrynB - 2007-12-07 01:12:24

No way, Smitty, you've got it all wrong. And that "dumb old country boy" line won't work with us -- you may be from Texas, but remember I grew up there too, so I know all about you guys who try to pull the "dumb old country boy line". So the real deal is that a bunch of us started a game behind your back. It's called "Stump Smitty" -- and the objective is to see who can come up with a question Smitty can't answer. And whoever does WINS!!! So I just might be on my way to winning the big game unless you come up with a good answer to the questions in this thread by the time the weekend is over. Up for the challenge Smitty?
So Ron, I thought it was the Superior Vena Cava (SVC) we've all got those leads threaded into -- a nurse friend of mine called it that once -- but for all I know the subclavian vein and the SVC are one and the same? Again I'm no expert, but I've read that doctors like to leave leads in as long as possible because extraction can be risky -- so even when we get a new PM, they use the same old leads as long as they're in good shape. And sometimes when the old lead fractures or otherwise becomes unuseable, they just cap it off and insert a new one. I recall one posting on this site where the person said an xray of their vein/heart looks like a set of teeth with braces on, because they had something like 8 or 10 or 12 (I don't recall) leads.
So can any of you medical folks shed some light on this? If not, Smitty will probably figure it out for us eventually. Or maybe Stepford_Wife (Dominique) will return from France and do one of her magical research tricks and turn up something interesting for us?
Take care all, Cathryn


by ronpage - 2007-12-07 11:12:01

Dunno which it is. I thought the doctor said yes when I asked him if the subclavian was the vein used. Since my hearing more or less left me long ago I sure wouldn't swear to anything I thought I heard. I'm much more comfortable thinking they are in the SVC since it apparently is so much larger in diameter.


by ronpage - 2007-12-07 12:12:39

Well, I was really hoping the "hair analogy" would be closer to the actual size. It sounds like the actual wire may be that size but the insulation bumps it up to about what I was seeing on the display. I'm sure this is something that we shouldn't worry about since so many have been implanted. Still, Cathryn's comment/question regarding how many leads, both active and inactive, might be in the subclavian vein is more than a little spooky. I guess I just assumed a dead lead would be extracted instead of being left in place. Seems like that would definitely limit the number of "redos" possible.

Smitty, thanks for doing the research. And, thanks for 'fessing up to not understanding what you wrote any more than we understood it. :-) Still, there was a lot of info there.

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