A programmable implantable micro-stimulator SoC with wireless telemetry: Application in closed-loop endocardial stimulation for cardiac pacemaker

Abstract

The use of closed-loop implantable telemetry devices [1,2] is increasing as recent clinical studies have shown their efficiency and usefulness in detecting and treating various cardiac arrhythmias. In this paper, we present a single-chip closed-loop system providing closed-loop feedback of sensed cardiac patterns. This device promises more optimized stimulation parameters to cure rapid arrhythmias compared with open-loop devices. Our system incorporates more functionality comparing with the conventional micro-stimulators, yet consumes less power. It is powered by implanted rechargeable batteries periodically charged by radio-frequency (RF) coupling. This improvement of the powering system can prevent improper device operation or shutdown due to RF coupling and loading variations. Furthermore, this system eliminates the need for periodic surgery for battery replacement and improves quality of life of the patient.In this work, an implantable micro-stimulator SoC (IMSoC) is designed as cardiac defibrillator for remote delivery of power by means of coupled coils supplying power to a bio-implanted rechargeable battery. The IMSoC consists of a smart control circuit for power management, an RF-coupling power system for battery charging [3], and 2 ultra-small rechargeable batteries as power supplies. The micro-stimulator circuit embedded in the IMSoC is externally powered and controlled by a single encoded RF carrier. Stimulus parameters, such as pulse width, amplitude, and frequency, can be programmed [4] from the remote controller.Using an implantable SoC with closed-loop functionality, stimulation can be dynamically adjusted according to the real-time heart rate (HR). To continuously acquire intracardiac electrograms (EGMs), a monitoring analog front-end (MAFE) is implemented to sense and detect the peak value of EGMs, and to achieve the closed-loop control of HR. To verify a prototype of the IMSoC in vivo, this study presents an example of an implantable RF power converter used to regulate endocardial pacing with closed-loop physiological feedback from a conscious rodent model.The block diagram of the closed-loop stimulation system with external device is presented in Fig. 2.6.1. The external device, including a battery-based digital signal processor (DSP) in pocket, transmits encoded data and charging energy to an in-body circuit via a set of coils. The modulated digital data acquired from the sensing channel is transmitted out-of-body through the same coils to save on coil area. A MAFE and pacing channel detect and stimulate the paced neuron, respectively, allowing the system controller to immediately program the stimulus parameters. The powering interface smartly manages batteries, providing low-and high-voltage power supplies for system operation and micro-stimulation, respectively.As shown in Fig. 2.6.2, the PSK demodulator based on a phase-locked loop (PLL) technique is proposed to recover the clock and data from received 256kHz carriers. The PLL synchronizes certain signals, such as PSK data, oscillating signa...

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Analysis and implementation of a fourth‐order bandpass filter for R‐wave detection of an implantable cardiac microstimulator

“…In recent years, implantable cardiac microstimulator devices, such as pacemakers, have been developed and reported . To acquire heartbeat signals, the analog front‐end circuitry , an essential interface between the lead (sensor) and signal processors, is required. A block diagram of the telemetry device for implantable cardiac microstimulators is shown in Figure .…”