A preliminary study of an implanted device powered by an inductive link for the telemetry of the epicardic electrocardiogram and the radionuclide activity of the left ventricle

Abstract

In nuclear cardiology, radionuclide data concerning the cardiac function are presently collected using external detectors, providing scintigraphic images or activity curves with respect to time. This paper presents a new approach to the latter kind of instruments, which are often called nuclear stethoscopes. This proposed system is composed of a cardiac implant, a miniature transmitter positioned externally on the chest and a remote receiver system allowing the processing of the cardiac function data. The transcutaneous magnetic link permits the power transfer in order to energize the electronic implant, and permits the telemetry of the electrocardiogram and the radionuclide data between the implant and the external receiver system. The nuclear activity measured by a photodiode for gamma rays based on cadmium telluride, with pulse width modulation, constitutes the carrier of the electrocardiographic activity. The composite signal is transmitted by means of the implant impedance modulation. The use of this transmission concept reduces to a minimum the volume of the implant. Furthermore, this system, allowing the correct positioning of the external transmitter facing the left ventricle, increases the performance of the global transmission system. Theoretical results on the design of the magnetic link are presented.