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

TL;DR

This study models the electro-thermal behavior of implantable lithium batteries in ICDs, revealing how continuous low-level discharge impacts battery lifespan more than high-energy shocks, aiding in device design improvements.

Contribution

It introduces a coupled electro-thermal dynamic model to analyze battery behavior under real ICD operating conditions, focusing on the effects of different discharge currents.

Findings

Battery voltage is mainly affected by small continuous discharge currents.

High-energy shocks have less impact on battery voltage than expected.

Model results can guide improvements in ICD battery design and longevity.

Abstract

This paper investigates the impact of implantable cardioverter defibrillator (ICD)'s load on its lithium battery power sources through a coupled electro-thermal dynamic model simulation. 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 (DOD) and temperature dynamics of the implantable lithium battery with a combined cathode material, namely carbon-monofluoride and silver vanadium oxide (Li/CFx-SVO). 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 affected by small but continuous housekeeping discharge current in the range of uA, rather than intermittent high defibrillation current demand in the range of several amps. The results can be used to improve the device design control and operation, thus extending the service life in patients and reducing the need for invasive replacement surgery.