Pacemaker interference

Link

by LondonAndy - 2017-03-04 18:50:58

Not sure what the full article says, but a snipet is at: http://circ.ahajournals.org/content/135/9/907 

You need to be an American Heart Association professional, or to pay $35, to see the full article.

Key point from the snippet is: "To date, there is no conclusive evidence for the extent to which sources of EMF may cause harmful electromagnetic interference (EMI) in patients with pacemakers or implantable cardioverter-defibrillators"

Pacemaker interference

by Selwyn - 2017-03-05 07:01:00

What the article also says`;

Patients were exposed to an EMF similar to common exposure, i.e. EMFs at power grid frequencies (50Hz or 60Hz), then increasing the EMF until the researchers noted a pacemaker sensing failure.

They found pacemakers are susceptible to EMF that can occur in everyday life in particular when programmed to maximum sensitivity or so-called unipolar sensing mode. Examples of EMF sources are powerlines, household appliances, electrical tools and entertainment electronics.

"In many cases, holding the appliance, tool or other EMF source at a forearm's length distance (greater than 12 inches) limits the risk of electromagnetic interference. But further measures might be needed in environments with strong EMF, such as engines used in the processing or manufacturing industry", Napp said.

There is no doubt that bipolar pacing is the safer programming option, I suggest 

See also this comment [ from, 'Cardiac device wearers should keep distance from smartphones' Date:June 22, 2015, European Society of Cardiology (ESC)] which also relates to high voltage cables - as when walking under them, between pylons:-

Dr Dyrda said: "There is no significant concern for patients with pacemakers programmed in the usual configuration (nominal settings, in bipolar mode). For the minority of patients with devices in unipolar mode or with very sensitive settings, counselling should be given at implantation or at medical follow¬-up."

Who needs unipolar? I have also recently posted on muscle twitching when I had unipolar settings.

Selwyn

Who needs unipolar setting ?

by IAN MC - 2017-03-05 15:32:56

Selwyn .  I am having a PM check-up tomorrow morning and will ask the question.

My understanding is that bipolar and  unipolar involve different parts of heart tissue to complete the circuit . I think in some situations such as unwanted diaphragmatic pacing a change in polarity ( either way  )  may help to remove the phrenic nerve from the circuitry and resolve the problem.   

But from your comments above it does seem that the increased sensitivity of unipolar is a disadvantage if you decide to get dangerously close to external EMF sources.  I wonder if this explains some of the posts in the past where people have experienced EMF interference.

Cheers

Ian

Let me suggest the following...

by donr - 2017-03-05 20:13:39

...when in Bipolar mode, the pacing current only has to pass across a very short distance - perhaps a Cm, at greatest.  The origin of the electron stream is at the tip of the lead, embedded in the heart wall.  The reception point of the stream is just a short distance back up the lead, in the blood stream, which is a great electrolyte, conducting electrons very well.  Also, the short distance between the two points means that the electric VOLTAGE field does not weaken very much over that distance.

Switch the same lead into the Unipolar mode, which can be done as a backup mode, and the origin of the electron stream is still the tip of the center conductor buried in the heart wall.  Since therre was a failure in the circuit that terminated in the blood stream just a Cm or so from the tip, the distance from the tip of the lead to the collector of the pacing pulse current now becomes the PM case,. several inches away - let's say 4 inches.  That translates into about 10 Cm, or about ten times further from the tip as in Bipolar mode functioning.  Addittionally, the case is about 100 times the surface area as the collector point near the tip of the lead.  Consequently, the voltage field is much lower in intensity, causing the sensitivity of the receiving circuits to be increased in order to sense the return electron flow, hence causing it to be more susceptible to stray EMF's.

Ian's observation about potential for interference causing problems for anyone whose PM is in Unipolar mode may well be valid.  We never hear what mode member's device is working in.  They probably don't know!

PM cases are made from Titanium (Ti), which is very impervious to corrosion in electrolytes - such as seawater & blood.  I cannot recall if it is because the surface of Ti instantly corrodes when placed in the electrolyte, & the oxidized Ti surface becomes highly resistant to furhter corrosion.  (That happens to Aluminum (Al)).  That would lead to lower conductivity, hence fewer electrons getting through the case surface & the increased sensitivity receiver circuits picking up the induce current due to interfering EMF's.

Donr    

Just back from the hospital !

by IAN MC - 2017-03-06 07:30:14

I have just had a treadmill test at the local hospital with a particularly attractive Medtronic rep ( female ) doing the PM adjustments.

I asked her about unipolar v bipolar modes but what was disconcerting was the fact that she would not have looked out of place in a Miss World contest.  I TRIED  to concentrate on her answer and I THINK she said :-

Bipolar is now the default mode setting . Unipolar is hardly ever used and is tried as a last resort in some situations 

I wonder , should I try to get another treadmill test ....  tomorrow maybe ?

Cheers

Ian

bipolar

by Tracey_E - 2017-03-06 11:57:34

They don't put them in unipolar unless there is a compelling reason, bipolar is the norm. They tried mine in unipolar once when a lead was bad and they were experimenting with working around it. I hated the feeling so they changed it back to bipolar. I could feel every beat like a little shock, it was awful. 

My lead is unipolar

by Grateful Heart - 2017-03-06 17:12:22

Well....at least part of it.  My LV lead was pacing my diaphragm something fierce.  Since I have a Bi-Vent CRT-D the LV lead is also the defib lead.  The EP basically spliced the LV lead, leaving the defib part intact and active and capped off the pacing side of the LV lead in order to stop my diaphragm from pacing.  He then inserted another lead (a 4th lead) for the pacing of my LV since I need both ventricles paced. 

My device is a Boston Scientific.  The 4th lead is unipolar and goes back to the PM case as Don explained. 

My leads configuration (Pace/ Sense) is:

Atrial.....Bipolar                    

Right Ventricular.....Bipolar    

Left Ventricular......LVtip>>Can / LVtip>>RV  

When you look at the programing computer in the office... you see the 3 leads functioning.  If you scroll down to the next page....you see the 4th lead.  My device nurse thought I was nuts (I could tell by her face) when I came in after the revision and told her I now have 4 active leads.  The device tech was there (a rarity) and he scrolled down on the computer and confirmed it.     

BTW, I wasn't supposed to know all of this.  The stand-in EP (not my original EP) made sure he told me....he thought it would upset me.....it didn't.  It made me want to learn more about my device and it's workings.  My EP wanted to know who told me and he was not happy.  I asked him if he would have handled it the same way and he said he would.....so that was comforting.                                    

I do feel everything and yes, sometimes like a little shock.  It's been 6 years since the revision.  It will be interesting to see how they handle the replacement when the time comes. 

I have talked about interference with my device on this site in the past re: magnetometers, some store security systems, etc.  Some others have noted interference as well.  There were some naysayers saying it was just not possible.....simply because it did not happen to them.  

I never talked about this in such detail here before because I didn't feel it would be received well (obviously) and I didn't want to frighten or confuse any newbies.  After Selwyn's post it seemed like the right time.

So the next time someone states they are feeling something strange or just not right....maybe we should keep an open mind. 

Grateful Heart 

GH: Thanks for ...

by donr - 2017-03-07 03:34:47

...bringing it up!  I, too, had a lead go Unipolar way back in yr 4 of my hosting duties.  Lead outer covering fractured & automatically went to Unipolar from Bipolar.  Boy did I know something was really WRONG - but not what it was.  What I was feeling was a tingling around my PM case - exactly like an electric shock!  Went to see my Cardio, who tested leads & discovered that resistance had gone up, but not why.  Well, naturally ther resistance went up - the return current was traveling through my body's electrolytes, a less good conductor than the outer sheath of the lead.  Also, it had to jump across gaps between muscle surfaces & through fascia & layers of body fat.  Go to a meat market & look at a steak - several muscles across the surface, separated by spaces & thin films of fascia to hold it all together.

For all of you who have read this far, WHY did I feel a tingling  around my PM case?  Why did GH feel sometrhing funny?  Simple.  Harken to the dead of winter in northern climes where it gets cold AND dry & static electricity bulds up in your body.  You walk up to your car, touch the metal door handle & KAZANG!!!!! you get fried by the static discharge.  You feel it in your hand/finger, right where you discharged the current & created an arc.  You sense it because where the arc meets your finger it's a high resistance & you feel energy being dissipated where the resistance is high & current flows through it.  You don't feel it in your body because the resistance is low in your electrolytes & a low resistance dissipates no energy.  You don't want to feel the shock?  Grab a car key, grip it very tighly between BARE thumb & index finger to get a good electrical connection, then touch the car w/ the tip of the key.  Voila!  You feel nothing.  The arc is now from key to car.  So - what does that long-winded discussion have to do w/ feeling a tingling at the PM case surface when in the Unipolar Mode?  Everything!  If you read my previous comment, about the PM case of Titanium becoming oxidized & a poor(er) conductor than your electrolytes, you'd realize that you now have the return current passing through a higher resistance, dissipating energy & your body sensing it.  You squeal out "Oooooooh, it tickles," squeal w/ surprise & probably quiver a bit.  All very natural!

GH - you have now earned your "Geek" Badge, authorized to be worn w/ a plastic pocket protector.  We will have to gather the old bunch aroud a flaming red pot-bellied stove in a pub near Ian's abode & have a formal presentation. Hopefully, Lady Bossy can make it from Indiana out in the snow drifts.

A quick question for Ian:  once upon a time while I was working in Old Marylebone Road right off Edgeware, they modernized a pub right there o Edgeware Road.  Being a crazy Yank, I wandered by one evening after dinner in a local restaurant w/ Mrs. Don & spied an old art glass window that had been removed fro the hulk of the bldg & was sitting on a pile of rubbish at kerbside.  I ripped it out of the pile, struggling to break some ligtht steel framing, & hauled it off into the underground to go to a band concert several miles north of there.  All the locals stared at me like I was mad, carrying this 3 ft square ratty old window, struggling to keep the dangling shards of metal under control.  Mrs. Don was trying to hide, just short of crawling under the benches.  She kept shaking her head & asking me "What are you ever going to do with that piece of junk?  Are you REALLY going to take it home with us?"  "Of course," I replied.  "It might be historic!  Maybe it survived the "Blitz" & they are just throwing it away!"  It is still in the same box I packed it in back in 1981.  Never found a use for it.   So...do I have a piece of history packed away, or is it just rubbish, awaiting its day to join Lenin on the "Rubbish heap of History"?

Did that side of London suffer a lot of bomb damage during WW-II?  I never thought to ask while I lived there.

Don

Great

by Cabg Patch - 2017-03-07 10:02:05

Last night I went to bed a perfectly normal person (no smart remarks) and this morning I wake and discover reading this thread I'm now Bi !!! Wasn't there just an executive order banning that?  So on top of it all I'm an illegal too...

Guys what is stated is true scientifically but bottom line almost nobody experiences real interference unless of course by a spouse. In the end, you're all going to die, stop worrying 

Fear Not Patch

by Grateful Heart - 2017-03-07 10:38:47

The good news is you're not Uni !!

No worries.  

Grateful Heart

Patch

by IAN MC - 2017-03-07 13:20:42

I wasn't worrying about anything until you said that we are all going to die  . I wish they had told me THAT before I agreed to have a pacemaker !!

Ian

PS  Don : i will send you a private message re bombs in London