The potential risk of electromagnetic interference with an implantable defibrillator has been frequently described including in the hospital environment, in the patient’s home or during his/her professional activities. Interference may occur by conduction if the patient is in direct contact with the emitting source or by radiation if the patient is within an electromagnetic field. The most recent ICDs are protected against the vast majority of sources of interference that the patient may encounter in his or her daily life. The parasitic signals are typically filtered, the analysis being restricted to a narrow bandpass corresponding to the physiological signals (high-pass and low-pass filters). However, the high adaptive sensitivity required in an ICD for accurate signal detection during ventricular fibrillation may favor the sensing of non-physiological signals corresponding to the same bandpass. Electromagnetic interference signals may not be appropriately filtered and lead to more or less severe consequences ranging from the occurrence of inappropriate therapies to pacing inhibition in a pacemaker-dependent patient, inappropriate mode switching due to false diagnosis of supraventricular arrhythmia, rapid ventricular pacing synchronized to atrial oversensing, suspension of therapy detection, or fallback to asynchronous mode. Exceptionally, interference with a high intensity electromagnetic field can cause permanent damage to the circuits.

The diagnosis of electromagnetic interference is based on the concordance between exposure to a source at the time of the episode and oversensing of characteristic signals (rapid, regular and saturating the baseline). Electromagnetic interference at the mains frequencies (60 Hz in the USA and 50 Hz in Europe) occurs when the patient is in physical contact with poorly insulated electrical equipment. If the oversensing is prolonged, a single electric shock is most often curative since the patient usually interrupts his activity immediately. Electromagnetic interference is more frequent for an integrated bipolar lead than for “true” bipolar sensing, the sensing antenna being wider. The characteristic high-frequency, non-physiological signals are sensed on the various available channels (possible diagnosis of dual tachycardia, AF + VF) and are generally of greater amplitude on the far-field channel than on the sensing (near-field) channel.

The main preventive measure consists of identifying the emitting source and avoiding the use of certain poorly insulated instruments. Since this patient was monitored remotely, we received an alert the next day and were able to link the sensed episode to the use of a poorly insulated domestic appliance.