Erroneous Magnet Positioning Leads to Failure of Inhibition of Inappropriate Shock during Fast Conducting Atrial Fibrillation Episodes.

We present the case of a 75-year-old patient with a single-chamber St. Jude Medical internal cardioverter defibrillator (ICD; St. Jude Medical, St. Paul, MN, USA) for primary prevention, who was admitted with 39 inappropriate ICD shocks because of atrial fibrillation with rapid ventricular frequention, despite magnet placement. Review of the device manual and literature revealed that apart from different responses to magnet placement programmed for the various manufacturers, the type of magnet and the positioning can be of specific interest. In the case presented, the donut-shaped magnet should have been placed off-center instead of directly over the device.