Effect of Magnetic Navigation Systems on St. Jude Medical Implantable Cardioverter Defibrillators (ICDs) and Pacemakers

(Medical Application by Stereotaxis Corporation)

Background

Stereotaxis magnetic navigation systems utilize strong magnetic fields, for example the Niobe model references magnetic flux density up to 0.08 Tesla (i.e., 800 Gauss). St. Jude Medical has not performed any formal testing with Stereotaxis systems and these magnetic fields could potentially interact with pacemakers and implantable cardioverter defibrillators (ICDs). The magnetic field from magnetic navigation systems may be interpreted as “electrical noise” in ICDs and cause a noise reversion. During a noise reversion, the device will not deliver therapy (therapy includes ATP pacing, cardioversion and defibrillation). If the external signals are misinterpreted as cardiac events in an ICD, inhibition of bradycardia pacing and/or inappropriate arrhythmia detection and therapy delivery are possible.

Potential effects

If the ICD is exposed to a constant magnetic field of sufficient strength, the detection circuitry will be temporarily interrupted, thereby disabling any tachyarrhythmia detection. Once the magnetic field is removed, arrhythmia detection is again enabled. It should be noted that ICDs can have their magnet response programmed to IGNORE the presence of a magnetic field and therefore continue to deliver therapy even in the presence of a magnetic field.

Magnet reversion will not affect the bradycardia pacing function in ICDs – bradycardia pacing will continue as programmed. In contrast, pacemakers will pace asynchronously when exposed to a magnetic field.

A summary of potential effects is provided in the table below and is based on device testing at St. Jude Medical, clinical experience and/or a review of the scientific literature.

Potential Effect Estimated Frequency
  Pacemakers ICDs
Failure to deliver needed therapy Not applicable Common
Asynchronous pacing due to magnetic field Common Not applicable
Total inhibition of pacing Rare Uncommon
Asynchronous pacing due to noise reversion Uncommon Uncommon
Inappropriate therapy delivery Not applicable Rare
Device reset or reversion to backup VVI pacing Rare Rare

Recommendations

If magnetic navigation system therapy is deemed medically necessary, the risk of interference can be reduced if the following recommendations are observed.

Pacemakers:

  • Ensure that the magnet response is programmed On or to Battery Test (or to Temporary Off in older models such as Trilogy). This will help prevent inhibition by asynchronously pacing at the magnet rate in the presence of a magnetic field.

ICDs:

  • Keep the Stereotaxis magnets stowed in their parked positions before the patient enters the room and during programmer telemetry with the ICD. The parked position leaves the magnets at their furthest position from the table.
  • Program the ICD to a non-tachyarrhythmia configuration using the appropriate St. Jude Medical programmer. Depending on the specific device, such programmable options are called “Tachy Therapy is Disabled” or “Zone Configuration Off”. When antitachyarrhythmia therapies are disabled, monitor the patient and ensure that external defibrillation capabilities are available.
  • Program the ICD to Pacer Off (only if the patient does not depend upon pacing support). In pacemaker-dependent patients, program the ICD to an asynchronous pacing mode.
  • Be alert for asynchronous pacing, pacer inhibition, or inappropriate therapy due to noise. If these effects are noticed, the ICD should automatically return to its programmed mode of operation when the patient is removed from this area.
  • After the patient has left the Stereotaxis room, the ICD should be programmed back to its original settings.

If you have any questions on this topic, please contact St. Jude Medical Technical Services at 800-722-3774.

PDF Effect of Magnetic Navigation Systems on St. Jude Medical Implantable Cardioverter Defibrillators (ICDs) and Pacemakers (29.5kb)
Rev. 03/09