Ineffective or inappropriate ICD shocks – Part 2


Inappropriate ICD shocks are not benign events. They can have profound psychological consequences for the patient, they can trigger ventricular dysrhythmias, and perhaps most importantly, they deplete the battery life of the device. Each shock reduces the battery longevity by about 30 days.

Often, paramedics (and many physicians) are reluctant to disable ICDs. That’s because we’re generally not experts when it comes to implantable medical devices. However, we should be experts in advanced cardiac life support.

Albert Einstein once said that the definition of insanity is doing the same thing over and over again and expecting a different result. If the ICD has shocked the patient 10, 11, or 12 times without a positive effect, why would we expect a benefit from shock number 13, 14, or 15?

I’m familiar with one case where a patient was hypokalemic which caused a prolonged QT interval with subsequent runs of torsades. The device shocked the patient incessantly but the torsades kept coming back until the potassium was replaced.

It’s important to consider the underlying cause. 

For the case presented in Part 1, the ICD is shocking a relatively slow wide complex tachycardia that is well tolerated by the patient. Would you shock it? If not, then you probably shouldn’t let the ICD shock it either.

Consider this algorithm from Emergency management of arrhythmias and/or shocks in patients with implantable cardioverter defibrillators (ICDs). A statement on behalf of the Resuscitation Council (UK), Heart Rhythm UK (formerly The British Pacing and Electrophysiology Group, BPEG), The Joint Royal Colleges Ambulance Liaison Committee (JRCALC) and the Ambulance Services Association (ASA). Resuscitation, Volume 71, Issue 3, Pages 278-282

ICD shock algorithm
Here’s another from Clinical Assessment and Management of Patients With Implanted Cardioverter-Defibrillators Presenting to Nonelectrophysiologists. Circulation 2004; 110:3866-3869.


Apply defibrillator pads as a backup. If the device is in the upper-right chest consider anterior-posterior pad placement.

anterior_posterior Image credit: Physio-Control

Most of the time an ICD will b implanted in the patient’s upper-left chest, so standard anterior-lateral pad placement works just fine.

In Part 3 we will go over the specifics of ring magnet application.

See also:

Inappropriate or ineffective ICD shocks Part 1

Inappropriate or ineffective ICD shocks Part 2

Inappropriate or ineffective ICD shocks Part 3

Updated 12/13/2015


  • Is there different rings for each manufacturer. Is the ring something the patient may have?

  • Tom B says:

    Adam – In all likelihood the patient will not have a ring magnet! That’s probably a good thing.Our ring magnets say Medtronic on them (because we got them through our Medtronic rep) but to my knowledge they should all work the same.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 cardiac 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.Tom

  • That’s a pro tip, Tom, on asking for the the device card.

  • Hey Tom,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. This article sort of gets to this with the St. Jude and Guidant models.

  • Any idea on the cost Tom. This sounds like something we should be utilizing.

  • Tom B says:

    Adam – They were free.Tom

  • Tom B says:

    Medic Intern for Life – I will contact Medtronic, St. Jude Medical, and Boston Scientific to get their official positions.I’ll let you know what I find out!Tom

  • Tom B says:

    Gentlemen – The short answer is that magnet application works for devices made by all three companies (Medtronic, St. Jude Medical, and Boston Scientific).In the process of contacting these companies I’ve learned a couple of interesting things, so I’ll be following up with one additional post in this series.Tom

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