Modulation Scheme Analysis for Low-Power Leadless Pacemaker Synchronization Based on Conductive Intracardiac Communication

Abstract

Conductive intracardiac communication (CIC) has been demonstrated as a promising concept for the synchronization of multi-chamber leadless cardiac pacemakers (LLPMs). To meet the 2-5 µW power budget of a LLPM, highly specialized CIC-transceivers, which make optimal use of the cardiac communication channel, need to be developed. However, a detailed investigation of the optimal communication parameters for CIC-based LLPM synchronization is missing so far. This work analyzes the intracardiac communication performance of two low-power modulation techniques, namely On-Off-Keying (OOK) and Manchesterencoded baseband transmission (BB-MAN), as a function of the transmitted bit-energy. The bit error rate (BER) of a prototype dual-chamber LLPM was determined both in simulation and invitro experiments on porcine hearts. A BER of 1e−4 was achieved with a median bit-energy in the range of 3-16 pJ (interquartile range: 4-15 pJ) for data rates from 75-500 kbps and a receiver Manuscript

A Direct-Digital 40 μA 100 kb/s Intracardiac Communication Receiver with 250 μs Startup Time for Low Duty-Cycle Leadless Pacemaker Synchronization

“…Moreover, relying on an external primary device increases the system's complexity and the risk of complications and may also compromise patient comfort. In the second category, RF communication and galvanic-coupled CIC have been extensively studied for direct implant-to-implant synchronization [6], [12], [17]- [23]. However, RF communication has not achieved adequately low power levels [17], [18].…”

“…In contrast, CIC has been demonstrated as an energy-efficient communication method for implant synchronization. This is attributed to the moderate attenuation of the intracardiac channel, relatively high electrode impedance (typically in the range of a few hundred ohms), and the utilization of low-frequency signals (ranging from 1 kHz to 20 MHz) [6], [12], [19]- [23].…”

“…DDC reduces current consumption compared to modulation approaches using a high-frequency carrier, since power-hungry modulation/demodulation circuits are avoided and the required receiver bandwidth only depends on the data rate. DDC is especially suited for intracardiac communication, which has a relatively flat channel frequency response and thus allows for distortionfree signal transmission without the need for equalizers [23]. Manchester-encoding has multiple system-level advantages due to being a self-clocking signal with zero DC component [32].…”

“…To generate the input signal and record the demodulated baseband bit-stream, an Analog Discovery 2 device from Digilent was used. Since previous work demonstrated a relatively flat frequency response for the intracardiac channel, the channel was modeled with a attenuation network consisting of four resistors [20], [21], [23]. The resistors were dimensioned to achieve a typical LLPM inter-electrode impedance of 400 Ω and channel attenuation of 60 dB [9], [20], [21], [23].…”

“…To this end, the average receiver current consumption I rx,avg is plotted against the estimated transmitter output current Îtx,out a typical communication scenario where one message of is transmitted every second. transmitter output current was calculated based on (11), using the reported values in Table III receiver sensitivity and data and typical intracardiac channel attenuation dB inter-electrode of 400 Ω [9], [21], [23]. As demonstrated in Fig.…”