Intermittent, erratic behaviour of an implantable cardioverter defibrillator secondary to a hidden magnetic source of interference.

Interference between pacemakers or implantable cardioverter-defibrillators (ICDs) and electromagnetic fields are of great concern due to the potential harmful influence on the function of the device. We report a case of intermittent, erratic behaviour of an ICD secondary to electromagnetic interference (EMI) caused by small magnets that were incorporated into the patient's clothing.