Effects of External Defibrillation/Cardioversion on St. Jude Medical Implantable Cardiac Rhythm Devices


External cardioversion/defibrillation delivers electrical energy to the heart in an attempt to terminate an arrhythmia and reestablish normal sinus rhythm. The energy produced from external defibrillation/cardioversion may cause loss of capture, transient inhibition, or damage to the pacemaker or implantable cardioverter defibrillator (ICD). Damage to the electrode-tissue interface may occur from the high energy levels used in external cardioversion/defibrillation, altering acute and long-term thresholds. In addition, defibrillation/cardioversion may cause the pacemaker or ICD to operate in backup VVI, pace asynchronously at a standby rate or in some cases damage the circuitry.

Potential effects

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
Loss of capture Common Common
Transient inhibition Uncommon  Uncommon
Asynchronous noise reversion pacing Uncommon  Uncommon
Damage to electrode-tissue interface Uncommon  Uncommon
Backup VVI mode  Uncommon  Uncommon
Damage to circuitry Rare  Rare


To reduce the possibility of damage to the circuitry, the following recommendations should be considered:

Patient management before therapy

  • Position defibrillation paddles as far from the pacemaker or ICD as possible (minimum of 5 inches [13 cm]).
  • Place the paddles in an anterior-posterior orientation. This will cause the energy vector to be perpendicular to the plane of the lead, which will minimize the energy coupled into the pacing or ICD lead.
  • Use the lowest clinically appropriate energy output.

Patient evaluation following completion of therapy

If inappropriate operation or damage is suspected, a thorough evaluation of the pacemaker or ICD system by the patient’s following physician may be considered.

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

PDF Effects of External Defibrillation/Cardioversion on St. Jude Medical Implantable Cardiac Rhythm Devices (18.7kb)
Rev. 03/09