Manufacturer-specific time-dependency of ICD magnet mode

Background: ICD magnet mode enables clinicians to interact with the device in a controlled and reversible manner by temporarily deactivating shock delivery. In previous investigations, we noticed that induction of magnet mode might be time-dependent according to ICD manufacturer. Therefore, the aim of this study was to systematically investigate the response of ICD from all major manufacturers to application of a magnet.

Methods: ICD from all manufacturers were utilized and connected to an interactive heart simulator (InterSim III, IB Lang). After ICD interrogation and activating tachy-therapies, an ICD magnet was placed over the device. Afterwards, ventricular fibrillation was simulated, and the ICD response was repeatedly analyzed both in the short and long term.

Results: Fifteen ICD (7 Biotronik, 2 Abbott, 2 Medtronic, 2 Boston Scientific, 2 Microport) were included in the study. ICD from the manufacturers Abbott, Boston Scientific, Medtronic and Microport reacted immediately to magnet application by inhibiting the antitachycardia function. Interestingly, none of the seven Biotronik ICD responded to a magnet directly after the end of device interrogation. In four Biotronik ICD (Rivacor 5 VR-T DX, Rivacor 3 VR-T, Inlexa 3 VR-T, Itrevia 5 HF-T QP), magnet mode was only inducible five minutes after the end of the interrogation. In a further three Biotronik ICD (Iforia 3 HF-T, Iforia 3 DR-T, Iforia 5 VR-T DX) magnet mode was only inducible seven minutes after the end of device interrogation. Within this period, antitachycardia pacing and shock delivery persisted despite magnet application. In addition, after eight hours of magnet application, the antitachycardia function was automatically and permanently reactivated in all Biotronik ICD. ICD from the manufacturers Abbott, Medtronic, Boston Scientific and Microport were still inhibited after eight hours of magnet application and shocks were not delivered.

Conclusion: This study is the first to systematically evaluate manufacturer-specific time-dependency of magnet mode induction in ICD. We were able to demonstrate that Biotronik ICD respond to magnet application with a delay after the device has been interrogated, in contrast to ICD from other manufacturers which respond immediately. When performing invasive procedures with devices that cause electrical interference, it is important to be aware that Biotronik ICD will not respond to a magnet until five to seven minutes after interrogation. Furthermore, Biotronik ICD reactivate shock delivery after eight hours of magnet application, which might be of importance in palliative care.