Search

Multi-node leadless pacemaker system overcomes the main limitations related to lead complications of the conventional cardiac pacemaker and will thus replace them in the near future. The multiple nodes of the technology require the development of low-power, low data-rate and energy-efficient communication framework for device synchronization and bi-directional communication between them. Moreover, the nodes need to communicate with the outer peripheral devices for data telemetry, control and remote monitoring. This paper focuses on evaluation of different energy-efficient modulation schemes at 433 MHz for bi-directional communication between the nodes using homogeneous liquid phantom model of human heart and living animal experiments. In this paper, we have analyzed three simple, low-budget modulation schemes - On Off-Keying (OOK), Frequency Shift-Keying (FSK), and Gaussian Frequency Shift-Keying (GFSK). The analysis is done based on the total transmitter power required to achieve a reliable communication indicated by the minimum threshold values of bit-error rate and packet-error rate. The experiments have been conducted for three common implant communication scenarios - in-body to in-body, in-body to on-body and in-body to off-body links. For conducting the experiments, we have designed the experimental setup with electronic components and fabricated antennas. The results have shown that GFSK has the best performance among the other modulation techniques based on the total transmitter power. We also investigated higher order of the same modulation schemes – 4-FSK and 4-GFSK. The results showed that GFSK performed much better than 4-FSK and 4-GFSK. This research will be carried forward to build the entire radio frequency communication framework for the multi-node pacemaker technology.

Conventional cardiac pacemakers provide effective treatment of patients with certain heart rhythm abnormalities but require intravascular leads associated with risk of complications and infections. Current leadless pacemakers – self-contained capsule-like pacemakers – diminish risks but offers only single-chamber stimulation adequate only for a fraction of patients in need of pacemakers since most patients require dual- or triple-chamber pacing. The optimal solution would be a system of multiple leadless pacemaker capsules that collectively provide multi-chamber pacing. To realize such a system, challenges including communication, power consumption, miniaturization and safety must be overcome. The thesis has contributed towards development of a communication framework of a novel multi-node pacemaker system. A communication network consisting of devices within the heart, in subcutaneous tissues and outside the body were investigated. The cardiac channel modelling was investigated through computational simulations in human voxel models followed by design of electronics and miniaturised antennas for experiments in liquid phantom solutions and living animals. The results showed that the optimal frequency of operation, based on the size constraints of the capsules, is located within the industrial, scientific and medical (ISM) band of 2.4 to 2.5 GHz. Our analysis suggests that the upper part of the abdominal wall provides the ideal position for a subcutaneous implant which may be utilized as a hub for capsule synchronisation and data storage. It was also evident that peak communication performance between intracardiac capsules occurs during end-systole and that the optimal modulation scheme for the communication framework is Gaussian frequency shift-keying (GFSK). Overall, this thesis has laid a foundation towards the development of a multi-node leadless pacemaker system which may improve the lives of millions of patients suffering from cardiac rhythm disorders.