Expect the unexpected: lead fracture in a subcutaneous defibrillator M. Doering*, F. Degenstein, G. Hindricks, and K. Bode Department of Electrophysiology, Heart Center Leipzig at University of Leipzig, Struempellstrasse 39, 04289 Leipzig, Germany *Corresponding author. Tel: +49 341 865 1413, Fax: +49 341 865 1460, Email: [email protected] A 60-year-old male patient with ischaemic cardiomyopathy presented with non-sustained ventricular oversensing and high-voltage impedance >400 ohm during routine follow-up 14 months after implantation of a subcutaneous defibrillator (Emblem S-ICD; Boston Scientific) for primary prevention. Panel A shows a stored electrogram with oversensing marked as noise or tachycardia and charging of the capacitor, as well as ventricular undersensing due to very low amplitudes. Interrogation revealed an unremarkable primary vector, but the secondary and alternative vectors showed R-waves with alternating amplitudes and artefacts during manual manipulation near the device or muscular tension (Panel B). The patient reported movements of the device so that he occasionally had to ‘adjust’ it. The X-ray showed a loss of continuity of the lead near the device (Panel C). Intraoperatively an almost complete fracture was observed (Panels D and E). After repositioning the device the day after the initial implantation due to unsuccessful defibrillation treshold (DFT) testing, the intermuscular device pocket was considerably enlarged and the device not adequately fixed. The electrode was replaced without complications, the device was fixed at both anchoring holes, and the pocket reduced in size. The DFT test was successful with 65 joules. Although lead fractures have not been reported in subcutaneous defibrillators so far, these should be included in differential diagnostic considerations. Adequate fixation of the devices in a properly prepared intermuscular pocket is mandatory to avoid unwanted movement of the devices and mechanical stress on the leads.