Appropriate Delivery of Antitachyarrhythmia Therapy Despite Magnet Placement Over Implanted Cardioverter-Defibrillator: A Case Report

Abstract

The fundamental perioperative concern for patients with implantable cardioverter-defibrillators (ICDs) is the potential for electromagnetic interference (EMI) from monopolar electrosurgery. The ICD may interpret electromagnetic signals as a tachyarrhythmia and deliver an inappropriate shock to the patient. Magnet placement is often used to avoid this problem since a magnet will often deactivate an ICD's tachyarrhythmia therapy. We report a case in which magnet placement over an ICD failed to suspend tachyarrhythmia therapy because of imprecise magnet positioning. This case demonstrates the possibility for error when relying on a magnet to suspend tachyarrhythmia therapies.

Figure 1.

Device interrogation. A, Detection of VF and tachyarrhythmia therapy. B, Initial magnet detection disabling tachyarrhythmia therapies was followed by intermittent periods of device activation. Although the magnet was never removed, magnet response was detected 6 discrete times. The red arrows in the figure indicate 2 distinct episodes of magnet detection separated by approximately 5 s. Since the magnet remained secured in place, repeated magnet detection is most likely related to failure to maintain an adequate magnetic field due to inaccurate placement. VF indicates ventricular fibrillation; VS, ventricle sensed.

Figure 2.

Magnet positioning. A, Abbott (formerly St Jude Medical) Fortify Assura DR. The arc of the magnet is positioned over the right or left side of the device. B, Biotronik Intica VR-T DX Magnet is positioned off center with the arc slightly above the housing. The arrow denotes the space between the arc of the magnet and the top of the generator. C, Boston Scientific Mini ICD, (D) Medtronic Evera XT DR, and (E) MicroPort (formerly Sorin) Platinium Magnet centered over the device. ICD, implantable cardioverter-defibrillator.