OVERSENSING AS A CAUSE OF INAPPROPRIATE IMPLANTABLE CARDIOVERTER- DEFIBRILLATOR THERAPY - CASE REPORT

Technology development in the recent years has enabled that both prevention and treatment of life-threatening heart rhythm disorders are managed by implantable cardioverter-defibrillators. Clinical studies have confirmed the advantage of this type of therapy in the prevention of sudden cardiac death in the recent years, so the use of ICDs has became a clinical routine. Rarely functional disturbances of those devices could be seen as undetected malignant arrhythmias (undersensing) or false detection of a normal heart rhythm (oversensing). Patient N.S. aged 67 years was admitted to Cardiology Clinic, Clinical Center Nis because of inappropriate sequential therapy of implantable cardioverter-defibrillator (ICD) (12 shocks were delivered within 48 hours before admission). ICD pacemaker was implanted four years before the admission due to dilated cardiomyopathy (LVEF 25%). Based on a detailed analysis of the device’s parameters the rapid increase in ventricular lead impedance was established (it was > 3000Ω; and the normal range is 250-2000 Ω). It was found that oversensing was the cause of sequential shocks delivery with energy of 35 J. The damaged lead of the ICD detected false signals as VF (ventricular fibrillation) and applied therapy. On the third day of hospitalization, the patient received an ICD Medtronic Maximo II device with the active electrode Medtronic Sprint Quattro 6947 but the left atrial electrode was not displaced. Prophylactic antibiotic therapy was given and patient was discharged 5 days after implantation. After one month at the control visit device parameters were satisfactory, the sensing function was appropriate with good impedance of the lead. Special feature of these devices is the need for individual programming, tailored to each patient, so it is necessary for a center that performs the implantation to have a medical team that has experience in the application of this type of therapy. Acta Medica Medianae 2013;52(4):44-47.