Hybrid Cathode Lithium Battery Discharge Simulation for Implantable Cardioverter Defibrillators Using a Coupled Electro-Thermal Dynamic Model.

Abstract

This paper explores the effect of the load imposed by implantable cardioverter defibrillators (ICDs) on their lithium battery power sources longevity using a simulation approach that incorporates a coupled electro-thermal dynamic model. ICDs are one of the effective treatments available to significantly improve survival of patients with fatal arrhythmia (abnormal heart rhythm) disorders. Using a lithium battery power source, this life-saving device sends electrical shocks or pulses to regulate the heartbeat. The service life and reliability of an ICD is primarily expressed by its battery's lifespan and performance. In this paper we investigate the terminal voltage, depth of discharge and temperature dynamics of the implantable lithium battery with a combined cathode material, namely silver vanadium oxide and carbon-monofluoride (Li/SVO-CFx). Modeling the implantable batteries characteristics is a well-established topic in literature; however, to the best of the author's knowledge, the impact of the high-energy shocks (defibrillation) and low-energy device power supply (housekeeping) on the ICD's battery operation is relatively less-explored. Our analysis reveals that the battery terminal voltage is primarily influenced by the continuous low-level housekeeping discharge current within the range of micro amps, rather than the intermittent high-level demand of defibrillation current within the range of several amperes. A Monte Carlo simulation and model prediction comparison with real-time experimental data from literature were used to assess the accuracy and applicability of the model. The results can be used to improve the device battery design, control and operation, thus extending the service life in patients and reducing the need for invasive replacement surgery.