Efficient Wirelessly-Powered Biotelemetric System for IoMT-Enabled Leadless Pacemakers in Dynamic Cardiac Environments

Abstract

Leadless cardiac pacemakers (LCPs) enhance health technology by offering a minimally invasive and reliable solution for cardiac pacing; however, their reliance on batteries poses a challenge to achieving extended device longevity. This study proposes an efficient wireless power transfer (WPT) system for LCP devices, in which the dynamic misalignments caused by the natural contraction and relaxation of heart muscles during cardiac cycles and respiratory movements are characterized for the first time. The system comprised an off-body transmitter (Tx) and an in-body rectifier-integrated conformal receiver antenna (Rx). A single-band Tx is optimized to deliver the power wirelessly in the 915 MHz frequency band, whereas the Rx element is configured to offer dual-band characteristics at 433 MHz (data-telemetric mode) and 915 MHz (power reception mode). In addition to the peak gains of -30.6 and -24.8 dBi at the respective lower and higher frequency bands, the Rx exhibited a wireless power reception efficiency of up to 0.53% with a harvested voltage of more than 3 V at 55 mm Tx-Rx separation. The simulation results were experimentally validated in a heart-mimicking phantom, demonstrating the effectiveness of the proposed WPT system in maintaining robust power delivery even in the presence of misalignments induced by physiological motions. Moreover, the rectifier's measured efficiency of 82% emphasizes its effective power delivery from the perspective of commercial pacemakers. In addition, a WPT-enabled real-time wireless biotelemetric communication link was established, highlighting the system's potential as a versatile Internet of Medical Things (IoMT) platform for monitoring various real-time physiological parameters.