Lead Noise

Pacemaker recording of electromagnetic radiation.

by Selwyn - 2017-11-07 07:30:02

I have a malfunctioning ventricular lead at present. This is shown by increased voltage needed to produce a ventricular contraction ( now 3.75V). Interesting the impedance for the lead remains the same ( normally if the lead is broken, this would increase). I now have 3 monthly checks to carefully monitoring the battery as there is a danger of rapidly exhausting the battery. It is presumed that my problem relates to the implant site and that I will need a new lead once it finally exhausts my battery. 

I have had radiotherapy- the machine caused my PM to malfunction, though it corrected itself once the electormagnetic radiation was removed. The casing of PMs shield us from most of the minor electromagnetic fields. Extreme elctromagnetic fields may wreck PM circuits.

I am not aware of how the PM would record 'noise'. The normal check up  detects sensed and paced events for upper and lower chmabers of the heart, battery, impedance, mode switching, pacing thresholds, refractory periods, blanking, etc. 

I suspect a search of the club site archives would produce quite a bit of information ( upper right corner.

Regards,

Selwyn

lead noise

by Tracey_E - 2017-11-07 11:02:37

When the impedance went up on one of my leads, they called it noise and it showed up on the interrogation report. It was still pacing but over time they had to keep turning up the juice to get the signal through. They compared it to running the air conditioner with the window open, the house still cools but the power bill goes up. The insulation wearing on the lead was the open window. It lasted for more than 5 years like that until it got bad enough to do anythig about it, and then we still waited until the current battery died and did it all at once. In my case, and I hope for your son, it was not a big deal, just something to keep an eye on. 

Let's talk abut ...

by donr - 2017-11-07 11:42:20

...noise as an electrical engineer.  To me, noise is any signal I don't want!  It's that simple.Were I niteerested in listening to noise & I heard a symphony, That would be noise!

Noise can be caused by anything that disturbs the system.  Selwnyn's noise caused by radiation therapy was ocurring at the smallest atomic level events you can imagine.  That rdiation his PM was exposed to was of such high frequency and was so intense that it got down into the tiniest recesses of the atoms making up his PM that they were bouncing around like rubber balls in a very random fashion, causing signal variation that confused the system.  NO!  They did not cause his device to become radioactive (Subject of another small monograph, Watson!)  

As to your case - a small crack in a lead's outer insulation & shielding  couild allow stray radio frequency signals (NOISE) int the main conductor and create unwanted variation in the PM's signals (NOISE).  That happened to me at the 4 yr point w/ my first PM leads.  Took weeks for the Cardio team treating me to figure it sll out.  At one point, we had a Cardio, his head nurse, an EE (me) huddled around an X-ray image trying to find a break in a lead.  It is completely possible for there to be a microscopic crack that rubs the two edges back & forth causing variations in electrical resistance at that point & causing variation IN SIGNAL STRENGTH - NOISE.     

Resistance can change based purely on the condition of the wires - for instance from the constant bending they get inthe heart from the blood flow whipping them back & forth.  Ever break a wire by repeatedly bending it back & forth?   That bending can make the wire more brittle at one spot, increasing the resistance (Impedance).

Believe it or not, the leads are the weak point in the entire PM system.  Far less reliable than the PM & all its pot full of electronic circuits.  so don't be amazed by this problem.  Count me as no. three at having a lead fail out of the three responses you have. 

Donr

Lead Extraction?

by natlat - 2017-12-01 07:49:06

I just had my right ventricular lead extracted.  The R wave was down to 1 and my lead was making alot of noise.  Another smaller hospital originally put this lead in the apex right in a scar there 3 years ago.  I have a scar in the apex and no one could diagnose me nor why.  I had an ablation two years ago in the vicinity of the apex lead which fixed my VT and I have been off meds and running and vt free ever since.  However the lead in the apex was failing and they think that it could be caused by fibrosis and/or the fact the ablation was in the vicinity of the lead.  They are sending the lead to the facility to be tested.  

Is fibrosis a common cause of lead problems?

Lead Extraction?

by natlat - 2017-12-01 07:49:33

I just had my right ventricular lead extracted.  The R wave was down to 1 and my lead was making alot of noise.  Another smaller hospital originally put this lead in the apex right in a scar there 3 years ago.  I have a scar in the apex and no one could diagnose me nor why.  I had an ablation two years ago in the vicinity of the apex lead which fixed my VT and I have been off meds and running and vt free ever since.  However the lead in the apex was failing and they think that it could be caused by fibrosis and/or the fact the ablation was in the vicinity of the lead.  They are sending the lead to the facility to be tested.  

Is fibrosis a common cause of lead problems?