Erroneous Magnet Positioning Leads to Failure of Inhibition of Inappropriate Shock during Fast Conducting Atrial Fibrillation Episodes (original) (raw)

2017, Pacing and Clinical Electrophysiology

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. (PACE 2017; 00:1-3) magnet response, ICD shock, implantable defibrillator therapy Case Report A 75-year-old male patient was presented to the emergency department with multiple internal cardioverter defibrillator (ICD) shocks. He received a single-chamber ICD 2 weeks prior (St. Jude Medical Fortify Assura VR1359-40QC, St. Jude Medical, St. Paul, MN, USA) for primary prevention. His medical history consisted of ischemic cardiomyopathy with a left ventricular ejection fraction of 30% and permanent atrial fibrillation (AF) for which he was treated with metoprolol 300 mg/day for rate control. The device was programmed with a monitor zone >160 beats/min, a ventricular tachycardia (VT) zone >190 beats/min with antitachycardia pacing (ATP) and shocks, and a ventricular fibrillation zone >222 beats/min with ATP and shocks. As discriminators, morphology (90% match), sudden onset (onset delta 20 ms), and interval stability (stability delta 40 ms) were programmed, with two out of three discrimination criteria requested to indicate VT. The electrocardiogram at presentation showed AF with a fast ventricular rate of approximately 200 beats/min. Hereby inappropriate therapy was delivered. Attempts to disable ICD therapy by placement of a magnet on the ICD were unsuccessful. In-hospital