What can cause broken leads?

iT WOULD TAKE...

by donr - 2017-11-18 13:45:06

...one heck of a crushing chest injury to break a lead.  The lead is surrounded by soft tissue, which would cushion the lead against anything short of a penetrating wound by something sharp.  There is no way that you could sever it by your physical motions alone - it would take the assistance of other parts of the body & it would take repetive action - f'rinstance getting the lead trapped between the collar bone & the top rib.  That, plus repetitive motion by your shoulder abrading the lead between the two bones could cause it to sever.

A common cause of lead failure is caused by metal fatigue.  That's bending the lead back & forth at the same spot till the metal in the leads hardens to the point it becomes brittle & then fractures at that spot.  I had that happen at the 4 yr point w/ one of my first leads.  The leads are NOT a single strand of wire.  They are "Coaxial" with a single conductor at the center - the signal carryng conductor, & an outer braided sheath for flexibility.  Between them is a polymer filler to insuate them from one another & give the lead a decent amount of stiffness.  Suppose whie being installed the outer sheath gets squeezed to the point the polymer gets flattened at one spot - possible by a sloppy surgeon, or even a very narrow space between the collarbone & rib.  If that portion of the lead gets flexed enough times, it could easily cause such a frature. That's called a "Fatigue Fracture" Common in everyday situations with metal subject to flexing - like airplane wings, tails, etc.  Another item subject to such brittle, fatigue fracture is pressure vessels - like air tanks or welds along seams in ship's hulls.

This is part of what makes leads the weak link in the PM system.  Look at how many times per day a heart beats - about 100,000 times!  That's nearly 3 MILLION times in a month.  Those leads see reversals in flow that many times per day and are subjected to a lot of dynamic forces that can cause these sorts of problems.

Donr

Donr 

Breaking leads

by Rhythmstorm - 2017-11-18 14:45:08

Makes sense, Don, thanks......

Broken Leads

by Sylvia1 - 2017-11-19 17:55:41

My husbands lead broke when he slipped getting out of the bath, and apparently he broke his collarbone on falling and the sharp edge sliced through the lead like a machete.It took 3 months when having a routine device check on his ICD to notice as he miraculously had no symptoms so they decided to remove the leads and also put a new ICD in as the other lead was also damaged.Damm baths - had a shower fitted straight after.