An electrical extension of automata-based heart models for closed-loop validation of pacemakers

Abstract

The development of implantable medical devices is challenging as must be guaranteed their safety, security and functional correctness. Current certification process is based on an open-loop approach, thus not considering the interaction between the pacemaker and the cardiac conduction system. Recently, an automata-based model has been proposed in order to close the loop and tackle this problem. However, as this model does not consider the electrical characteristics of pacemaker and heart signals, hardware-related problems are still a great concern. In this paper, it is introduced a new electrode-tissue interface to extend the existent automata-based model. By closing the loop using the proposed approach, the system can take into consideration new properties such as the energy provided by the pacemaker to stimulate the heart. Thus, based on the strength-duration curve, one can verify if a depolarization event was carried out. Indeed, depolarization of action potentials triggers an intracardiac electrogram generator that controls a voltage source at the electrode-tissue interface, providing the electrical signal to the pacemaker sensing system. This extension allowed to represent the pacemaker sensing, pacing, and battery circuits, as well as to evaluate the real scenario of stimulation and the effects of cardiac electrical parameters on its efficacy. The proposed model enables to include and test the pacemaker hardware specifications and evaluate more realistic scenarios of oversensing, undersensing, and failure-to-capture with a closed-loop heart.