I write in response to a letter published in the Spring 1998 APSF Newsletter titled, "ICPDs Require Preop Care". I am a Technical Consultant at Guidant Cardiac Rhythm Management. Guidant/CRM manufacturers Automatic Implantable Cardioverter Defibrillators (AICDs) which are discussed in the Newsletter article. We recently received a call from an anesthesiologist who was referencing the newsletter article while preparing a patient with an AICD for a surgical procedure. She pointed out that the article did not accurately describe the behavior that she observed in that no tones were heard when a magnet was placed over the Guidant AICD.Since the letter was published two years ago, Guidant (as well as other AICD manufacturers) has released new AICD models that have more complex magnet behaviors. I would like to clarify the procedure for using a magnet to deactivate a Guidant AICD.

CAUTION. Do not apply the magnet for more than 30 seconds as this may deactivate the device.

• Position a magnet over the Guidant AICD (we recommend the model 6860 doughnut magnet).
• If R-wave synchronous beeping tones are heard, the tachy mode is MONITOR + THERAPY.
• If a continuous tone is heard, the tachy mode is OFF or MONITOR ONLY.
• If no tones are heard, the magnet may not be properly positioned over the device, or the device may be programmed to ignore the magnet. In this case, a Guidant programmer is required.

To change the Tachy Mode of the pulse generator:

• Position a magnet over the Guidant AICD and hold in place for at least 30 seconds.
• If the CHANGE TACHY MODE WITH MAGNET feature is programmed ON, the TACHY MODE (and the tones) will change as shown in the chart on the summary below. To change the TACHY MODE again, remove the magnet for at least 2 seconds and reapply it to the pulse generator as indicated in the previous step.
• If the CHANGE TACHY MODE WITH MAGNET feature is programmed OFF, the TACHY MODE and the tones emitted by the device will not change after 30 seconds of continuous magnet application. In this case, a magnet may be taped over the device to temporarily suspend tachy therapy delivery. When the magnet is removed, the device will resume normal operation.

Please direct any questions you might have to Guidant Technical Services 1-800-CARDIAC