The implantable cardioverter-defibrillator (ICD) is an advanced medical device for preventing sudden cardiac death in patients at high risk of life-threatening ventricular arrhythmias. Because the device continuously analyzes intracardiac electrical signals in the millivolt range, its reliable operation strongly depends on a stable electrical environment. The occurrence of external electromagnetic interference (EMI) or leakage currents can lead to oversensing, which the device misinterprets as a pathological arrhythmia, consequently triggering an inappropriate and painful defibrillation shock.
The motivation for this master's thesis stems from real-world clinical incidents in swimming pool environments, where patients with implanted ICDs experienced inappropriate shocks. Ion-enriched water acts as a conductive medium, and faults in electrical pool equipment (e.g., pumps, underwater lights, salt chlorinator systems) or inadequate grounding can cause alternating current (AC) to leak into the water. The primary objective of this research was to systematically analyze the mechanisms of these electromagnetic interactions and to develop an appropriate measurement setup to simulate the conditions that lead to false device sensing.
The theoretical part of the thesis discusses the anatomy and electrophysiology of the human heart, the mechanisms of arrhythmias, and the operating principles and design characteristics of modern ICD systems. In the experimental part, an equivalent electrical model of the human body (RC circuit) was developed, enabling safe and reproducible testing of external influences on the device without direct biological exposure. Measurements were performed on single-chamber (VR) and dual-chamber (DR) ICD systems using a function generator.
The results demonstrated that even relatively low amplitudes of alternating voltage at a power-line frequency of 50 Hz and 60 Hz (in the range of 260 mV to 360 mV) can cause false detection of ventricular fibrillation (VF). The highest sensitivity to conducted electrical interference was exhibited by the RV tip/RV coil configuration. The findings confirm the high risk posed by leakage currents in swimming pools and provide a technical foundation for further safety analysis of pool facilities, as well as the formulation of strict safety guidelines for patients with implantable cardiac devices.
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