Three cases illustrate why magnets should not be placed over pacemakers or defibrillators before surgery. (Image source: Thinkstock)

Three cases illustrate why magnets should not be placed over pacemakers or defibrillators before surgery. (Image source: Thinkstock)

The American Society of Anesthesiologists advises against the routine use of a magnet over an implantable cardioverter-debrillator or pacemaker in its 2011 Practice Advisory for cardiac implantable external devices (CIEDs). Instead, the ASA advice is to interrogate the device to assess function.

In this month’s issue of Anesthesia & Analgesia, the article “Use Caution When Applying Magnets to Pacemakers or Defibrillators for Surgery” by Dr. Peter M. Schulman (Department of Anesthesiology & Perioperative Medicine, Oregon Health and Science University, Portland, Oregon) and corresponding author Dr. Marc A. Rozner (Department of Anesthesiology and Perioperative Medicine, Department of Cardiology, University of Texas MD Anderson Cancer Center, Houston, Texas) describes three patients from three institutions who suffered harm after use of a magnet.

One patient, a 33-year-old man with third-degree heart block, had a pacemaker.  He had sinus rhythm, heart rate 75-80 bpm, with ventricular pacing that tracked atrial function to produce atrioventicular synchrony.  A magnet was applied to increase heart rate from 75 to 100 bpm when he became hypotensive after receiving sedation.  Though the magnet induced asynchronous AV pacing with a heart rate of 100, atrial capture failed, ventricular electrical alternans ensued, and the patient’s hemodynamics were compromised.

A second patient had a biventricular implantable cardioverter-defibrillator (ICD).  When a magnet was placed over the device, the anesthesiologist did not realize the device had a disabled magnet switch.  Electromagnet interference resulted in antitachycardia pacing.

A third patient also had an ICD.  This patient also had a magnet placed over the device, but the device had a disabled magnet switch.  During surgery, the magnet shocked at least 20 times and antitachycardia pacing occurred at least 12 times.  This activity resulted in premature depletion of the ICD battery and the ICD device had to ultimately be replaced.

In their accompanying editorial “Perioperative Management of Pacemakers and Implantable Cardioverter Defibrillators: It’s Not Just About the Magnet” Drs. G. Alec Rooke, and T. Andrew Bowdle, Department of Anesthesiology and Pain Medicine, University of Washington School of Medicine, Seattle, Washington, conclude that “[t]he anesthesiologist should enter the surgery with as clear an understanding as possible of the status and function of the device, including how the device will respond to a magnet.”