Leads

How long is a piece of string?

by donr - 2019-01-31 12:42:40

Can't say precisely, but here's a short discussion:

1)  Depends on how big you are - leads come in several different lengths.

45, 53, 52, 58 cm. 

2) They are very small in diameter, not much bigger than a millimeter, so you can place three of them in the same vein w/o crowding.  I am 5'6" tall and have three leads in one vein.  Many women have three leads in the same vein, so it is not an unusual situation.

3)  How much of the lead is within the heart?  Obviously it is less for the Atrial lead because that is where the leads enter the heart.  The business end of the lead  - the part that is implanted in the wall - is only a couple mm long, and the remainder of the active electrical part is but about 9 mm long,  so ther is not much more in the heart - just the lead going tothe entry point.  THey leave some slack in that part of the lead, so there is peobably 5 cm of lead for the atrial lead inside the heart.  The lead is not initially pulled tight through the vein, but with time, the lead becomes afixed to the vein wall & is immobilized all the way back to the entry point into the vein.  The vein length dependds on how tall you are.  The lead is afixed to the entry point by a gizmo that is sutured to the vein & the lead, so the lead does not slide in and out of the vein.  All excess lead is coiled beside the PM case, so you are hard-pressed to pull on the lead outside the entry point into the vein.  MOF, it is darned near imposssible to pull al the slack out of the lead by pulling on the PM case.  Inside the vein, the lead becomes tightly bound to the vein, so you cannot pull that slack out w/o pulling on the vein. 

4)  There is a bit of slack inside the heart because the tip is usually a helix - screw - that is twisted into the heart wall and holds that end quite tightly.  How tightly, you ask?  I had an auto accident with a new lead 12 weeks old.  The impact was so great that it caused an aneurysm in my aorta - but the lead did not budge! Consider the blood flow through he atria - surrounding the loose, floppy lead - that lead - about 5 cm long - gets whipped around pretty violently every time the blood flows & then suddeenly stops flowing when the valve at the wall between the atria & ventricle closes.  That's about 100,000 times per day!

5)  Now for the Ventricular lead.  The heart is about 5" long (12 cm).  The ventricular lead is usaually implanted at the far end of the hearrt, so there is about 4.5 " of unattached lead between the entry vein and the implant point.  All the details about  the atrial lead between the PM case & the entry point into the vein apply.

Hope this helps your understanding of what goes on inside your body w/ a PM installed.

Donr

Lead dislodging .

by Selwyn - 2019-02-01 09:13:24

The leads have a small screw that attaches itself into the heart muscle. For correct pacing the tip of the lead needs to be placed against heart muscle ( a bit like connecting any battery).

The longer the lead has been in the muscle the less chance that it will come out. There tends to be scar tissure formed with the pacing processs. Rates of detachment vary with age, and where the lead is situated- perhaps 3-5% detach, and 0.1% or so totally perforate the heart muscle.

Personally, I have tried to put out leads ( on the dead) and find it is quite traumatic. ( PMs explode in the cremation process!).

The cardiologists have special catheter lasers, and/or drills etc. to remove leads if required.

The vein used plays very little part with regard to stopping lead detachment- a little fibrous tissue forms around the lead once it is inserted into a vein, this can be easily be broken down with a little movement.