Too Much Information About AICD Function


A 350+ pound man comes in for evaluation after his cardiac defibrillator discharged.

When defibrillators discharge once, there isn’t a lot to do with the patients. The defibrillator did what it was designed to do – sense and terminate an abnormal cardiac rhythm.

When there are multiple shocks, that is a different story. Multiple things to worry about including persistent abnormal rhythm, MI where ST changes are being sensed as an abnormal rhythm, lead fractures, loose connections, and electrolyte abnormalities – to name a few. Patients with multiple defibrillator discharges need their defibrillators interrogated and usually need to be admitted to the hospital.

By the way – All you docs out there know what to do if you use a magnet to temporarily deactivate an AICD in morbidly obese patients and it doesn’t work because of all the adipose tissue? And what do you do to keep the pacemaker function of an AICD working once the magnet does deactivate the AICD? Check in the comments section for the answers.

Fortunately, in this patient there was only one shock and we didn’t have to worry about bad things. We did an EKG just as a screen, but nothing else. Then we let the patient’s cardiologist know what happened and we sent the patient home.

Buuut … the thing that was memorable about this patient was how he described what he was doing when his defibrillator discharge. To wit:

“I was mounting my old lady when all of a sudden ‘BAM!’ Damn near knocked me off the bed when it went off.”

Well, cowboy, thanks to modern technology, you’ll live to ride another rodeo.



  1. If your magnet doesn’t work on an obese patient, get a second magnet, stick them together and then put them on the patient’s chest. The combined magnetic field is usually sufficient to deactivate the AICD in even morbidly obese patients.
    If the defibrillator has a pacing function (not all of them do), deactivating the AICD with a magnet has no effect on the pacing function, so you don’t need to do anything to keep the pacer working.

  2. I suspect that he may have met his rate threshold for shock delivery and that he may not have had an actual VT/VF event given the scenario. Hope he follows up with his EP doc for interrogation before he re-enters the rodeo.
    Most ICDs (even single chamber ICDs) have the ability to do VVI pacing. General default setting is at 40 bpm.

  3. If two magnets dont work just wheel the patient into the nearest MRI – but dont get too near too avoid patient sticking to MRI… :-}

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