Implantable Cardioverter-Defibrillator Oversensing Due to Electric Shock

Introduction We described the first case of oversensing due to electric shock in Serbia, in a 54-year-old man who had implantable cardioverter-defibrillator (ICD). Case Outline In July 2002, the patient had acute anteroseptal myocardial infarction and ventricular fibrillation (VF) which was terminated with six defibrillation shocks of 360 J. Coronary angiography revealed 30% stenosis of circumflex artery, the left anterior descending coronary artery was recanalized and the right coronary artery was without stenosis. Left ventricular ejection fraction was 20%. In December 2003, an electrophysiology study was performed and ventricular tachycardia (VT) was induced and terminated with 200 J defibrillation shock. Single chamber ICD Medtronic Gem III VR was implanted in January 2004 and defibrillation threshold was 12 J. The patient was followed up during three years every three months and there were no VT/VF episodes and VT/VF therapies. In December 2007, the patient experienced electric shock through the fork while he was making barbecue on the electric grill. ICD recognized this event in VF zone (oversensing) and delivered defibrillation shock of 18 J. The electrogram of the episode showed ventricular sensing - intrinsic sinus rhythm with electric shock potentials which were misidentified as VF. After charge time of 3.16 seconds, ICD delivered defibrillation shock and sinus rhythm was still present. Conclusion Oversensing of ICD has different aetiology and the most common cause is supraventricular tachyarrhythmia.