In Part II of this series, Medic Intern for Life left me this comment:
Our EMS Agency ran a CE course a month ago and we had a Medtronic rep warn us that not all ICDs turn off when a ring magnet is applied. Medtronic’s does but a few other makers do not.
In an effort to make sure I was giving accurate information, I contacted each of the “Big 3″ implantable medical device companies (Boston Scientific, Medtronic, St. Jude Medical) and asked each of them how their ICDs would react to ring magnet application.
Before I go further, I’d just like to say how impressed I was with the response I got from all three companies.
This was nothing like dealing with the banking, cell phone, or computer industries!
- There were few tele-prompt menus keeping you away from live help.
- In each case, the person who answered the phone was friendly and courteous.
- If I needed to be transferred, I wasn’t randomly disconnected.
- The person who transferred the call stayed on the line and introduced me.
- The technical experts knew the products intimately.
- Questions were answered confidently.
- They followed up with emails.
In short, the implantable medical device industry understands customer service!
It was like dealing with Disney World!
So what did I find out?
It turns out that ring magnet application works on ICDs from all three companies, and not just Medtronic.
Here are the specifics.
Boston Scientific
When you apply a ring magnet to a Boston Scientific ICD, in most cases you will hear tones (or beeps) that correspond with the R waves on the ECG. In some cases, the device may simply beep once per second. This lets you know that you are in the right spot.
After about 30 seconds, you will hear a longer tone that indicates that tachy therapies are disabled.
At this point you remove the ring magnet.
To turn tachy therapy back on, you reverse the procedure.
If no tones are heard after you apply the ring magnet to a Boston Scientific ICD, you are either in the wrong spot, or the magnet feature has been disabled.
(Note: This feature was disabled on certain models of Boston Scientific ICDs due to an FDA Advisory.)
See also:
Using a Magnet to Temporarily Inhibit Tachy Therapy or Change Tachy Therapy to Off
CPR and External Defibrillation for Pacemaker and/or Defibrillator Patients
Medtronic
For ICDs made by Medtronic, you simply apply the ring magnet and tachy therapies are disabled as long as the ring magnet is applied. When the ring magnet is removed, tachy therapies will resume.
A technical consultant from Medtronic emailed me a document entitled “Magnet Use for Suspending Medtronic ICD Detection” (Rev B, 18-DEC-2007).
The document offers these instructions for magnet use:
- Locate the patient’s Medtronic ICD.
- Place the magnet directly over the Medtronic ICD (secure magnet to patient to prevent dislodgement from device). Leave the magnet in place for the duration of the procedure.*
- In this “magnet” mode, tachyarrhythmia detection and therapy is suspended and the ICD will not interpret EMI, e.g. from cautery, as an arrhythmia.
- If the device has Patient Alert™/ Care Alert™ Self-monitoring, you may hear a constant tone for 10-30 seconds when the magnet is first applied. If a pulsing tone or high/low alternating tone is heard with magnet application, contact the patient’s cardiologist or electrophysiologist.
- If a tachyarrhythmia occurs during the procedure and intervention is required, remove the magnet to restore permanently programmed detections and therapy or use external rescue. Removal of the magnet by at least two feet (61 cm) returns the device to permanently programmed operation.
- Magnet application does not affect the programmed bradycardia pacing mode. EMI from cautery could cause inhibition of pacing due to oversensing. If inhibition is noted on the ECG monitors, use short, intermittent and irregular bursts of cautery (e.g. less than one second in duration).
- Magnet removal returns the device to permanently programmed operation. Keep the magnet at least two feet (61cm) away from the implanted ICD device.
- Perform the following steps to ensure an electrical reset has not occurred. This can be performed on all Medtronic ICDs, except Jewel® AF 7250, Micro Jewel II™ 7223Cx, Micro Jewel® 7221 and Gem III®AT 7276.a. After 10 seconds of magnet removal, re-apply the magnet to the ICD and verify that no tone or a 10-30 second constant tone results. This indicates no electrical reset has taken place. If a pulsing tone or high/low alternating tone is heard with magnet application, an electrical reset may have occurred, then call Medtronic. b. Removal of the magnet returns the device to permanently programmed operation. Call Medtronic for sterilization instructions.* These instructions are used to disable ICDs during certain surgical procedures where EMI (electromagnetic interference) could cause the ICD to “oversense” and trigger inappropriate therapy.
St. Jude Medical
For ICDs made by St. Jude Medical, you simply apply the ring magnet and tachy therapies are disabled as long as the ring magnet is applied. When the ring magnet is removed, tachy therapies will resume.
A representative from St. Jude Medical emailed me a document entitled “Magnet Use for SJM Implanted Cardioverter-Defibrillators” (August 2008).
Interestingly, this document states:
The magnet should be positioned off-center so that the curve of the “donut” magnet is over the top or bottom end of the device as shown below. Improper magnet placement may hinder magnet activation and could lead to undesired delivered therapy.
This image appears in the document:
St. Jude Medical appears to be the only manufacturer who specifically recommends applying the ring magnet off-center.
Ask to see the patient’s ID card
As a final thought, you might consider asking the patient if s/he has an ID card for the device.
Consider this story I shared in the comments section of Part II:
We actually ran a call yesterday for a gentleman whose ICD had fired x4. He reported that he felt weak and dizzy just prior to the first shock (making us suspect the device was delivering appropriate therapy).
I asked him if he had a device ID card, and he presented one from Medtronic that identified the device as a Maximo II CRT-D.
Note: CRT-D means cardia
c resynchronization therapy defibrillator.
The card specifically stated that application of a ring magnet would inhibit the antitachycardia functions and leave the antibradycardia functions (pacing) intact.
It might be a good idea to ask to see the patient’s ID card to clarify exactly how the device will respond to application of the ring magnet.
Having said that, our protocol does not require card verification prior to applying the ring magnet, or that the ICD be a particular make or model.
If applying the ring magnet doesn’t have the desired effect, you should be in the same exact situation you were before!
See also:
Inappropriate or ineffective ICD shocks – Part I
Inappropriate or ineffective ICD shocks – Part II
Inappropriate or ineffective ICD shocks – Part III
Wow — that is some great info Tom. Thanks for following up!
My pleasue, MIFL. I’m glad you brought it up! Tom
Tom, this information MUST be included in the ICD protocol. Great work as always!
You read my mind, Pete.Tom
Great information. Thanks. Wondering if the manufacturers provide the patients with ring magnets to use for misfiring ICDs? The reason being that though our protocols may not include use of the ring magnets but we may run on a pt who has self-applied the device.
Metro Medic FF – I’m sure they don’t supply patients with ring magnets.Without continuous ECG monitoring, there’s no way for a patient to know whether or not the ICD is delivering appropriate therapy!Thanks for the comment.Tom
That’s what I figured. But I thought the question should be asked/answered anyway. Funny thing here. I spoke with a friend of mine who works in an ER in a rural area. He told me that he has seen two patients who self-transported with a magnet taped to their chest. Complaints were misfiring AICD. One guy told his wife “if I pass out, take this thing off me.” Rural engineering at its best! Both patients were lucky that they indeed had a malfunctioning device rather than a lethal arrhythmia.
And I asked how they obtained the magnets. Physician friend couldn’t recall the details.
“If I pass out, take this thing off of me.” Sure thing, honey! If I’m not in the other room getting another beer…Thanks for sharing, Metro Medic FF!
Tom
Two questions. 1.Yes, you stated you got one free from your Medtronic rep, but what about the rest of us? Should we contact one of the big three about obtaining one? 2. I am assuming the magnests differ by manufacturer? Can they be interchanged?I apologize for asking for such stupid questions, but my limited cranial capacity still has me scratching my head.
Shaggy – As far as I know, they all work exactly the same. Next time you’re in the ED, ask if they know where they got theirs. You could also ask one of the cardiologists when they have their pacemaker clinic and talk to one of the reps. Or, just give one of the device companies a call! Tom
That is now on my agenda. Thanks.
I have heard in England they give every ICD patient a magnet ring and tell them how to use it. I have one and my sister does too – we keep them on top of the frig. Instructions from ICD nurse – hold it over device – do not let someone else hold it on you – they do not know how you feel (dizzy or faint). Do not tape it on – because if you faint you want it to fall off. Got magnet free from Medtronic – must sign off that you understand what magnet does & how to use it. After 8 shocks in 30 min I really wanted a big magnet!
Great information! I am a Home Hospice RN researching these same types of issues. For ICD magnets, the big 3 will all mail free magnets upon phone request; Boston Scientific-1.800.227.3422; Medtronic-1.800.222.0331; St. Jude Medical-1.800.681.9293. All companies except Medtronic claim any ICD magnet can be used; per a Medtronic representative, it is recommended that only a “Model 9466 Patient Magnet” be used. Thanks again for sharing- I have been having trouble finding step-by-step published information for many ICD issues.
Thanks for the comment, “Shocking”! Good info.
Tom
As a device tech..I work with all 3 manufacturers checking/programming devices in clinic.. Just a couple other points.. From experience .. one ring magnet, regardless of where it came from will work on all the 'big 3'. They get their magnets pretty much from the same places, so the "medtronic 9466 patient magnet" has no signficant difference than any one elses. I have a Boston Scientific magnet on my device cart & it works just fine.. Also from experience, in 8 years, I have never had 1 device that was programmed to have the magnet feature turned off – it's a valuable safety feature, and most implanters/reps make sure its on.
We have never given a magnet to a patient – the chance of them turning it off during actual episodes would be too big of a liability. (gets a couple shocks… they or the family member doesn't want them to get shocked so they whip out the magnet). We tell our patients – if it goes off more than 1 time in a short period of time call 911. If it goes off multiple times it needs to be treated regardless.