Pacemaker Rhythm Setpoint Module Using Filtered Activity Signals
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Solution Overview
Problem
Existing leadless pacemakers face challenges in continuously optimizing pacing pulse rates to match patient activity with high power consumption and reduced accuracy due to processor wake-up delays, retrospective analysis, and masked signal components.
Innovation Solution
A module for calculating cardiac rhythm setpoints using a combination of digital filters and combiner stages to continuously adapt pacing rates based on patient activity, minimizing power consumption and maintaining control accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the processor is made active only for limited sampling periods to reduce power consumption, then energy use decreases, but the processor wake-up delay causes reduced accuracy in continuous rhythm optimization
Solution Approach 1:
The patent segments the processing tasks into two distinct parts: a microcontroller that handles only essential timing and control functions with minimal power consumption, and a separate digital signal processing unit that performs the computationally intensive rhythm optimization calculations. This segmentation allows each component to be optimized independently for its specific function, resolving the contradiction between low power consumption and high calculation accuracy.
2Measurement precision
If retrospective analysis over long duration is performed to account for hysteresis, then physiological accuracy improves, but processor cycles increase causing doubled power consumption
Solution Approach 1:
The patent implements preliminary action by pre-calculating and storing hysteresis compensation parameters and lookup tables during device manufacturing or initial setup. During operation, the processor simply retrieves these pre-computed values rather than performing complex retrospective analysis in real-time, thereby maintaining physiological accuracy while minimizing power consumption during actual pacing control.
3Speed
If the processor wake-up time is reduced for faster response, then rhythm adaptation speed improves, but power consumption during wake-up phase remains high
Solution Approach 1:
The patent extracts the power-intensive signal processing functions from the main microcontroller and places them in a dedicated digital signal processing unit that can operate continuously at low power. This extraction allows the microcontroller to maintain a low-power sleep mode while the dedicated processor handles continuous rhythm optimization without significantly increasing overall power consumption.
4Device complexity
If conventional battery is used in leadless implant, then device complexity is reduced, but device dimensions cannot be miniaturized
Solution Approach 1:
The patent applies parameter changes by transitioning from chemical energy storage (conventional battery) to mechanical energy harvesting through piezoelectric or electromagnetic transducers that convert heartbeats and body movements into electrical energy. This fundamental parameter change in the power supply mechanism enables significant size reduction while maintaining adequate power supply for the implantable device.
Data Source
AI summary
The module comprises: a conversion stage receiving as an input a sampled activity signal representative of the patient's instantaneous activity and outputting a first target value by application of a predetermined activity/cardiac rhythm function; a low-pass recursive digital filter calculating over a predetermined duration a moving average of the first target value issued by the conversion stage and outputting a second target value; and a combiner stage receiving as an input the first target value and the second target HR value issued by the first low-pass digital filtering stage, determining the maximum of both target values and outputting the setpoint value to control the pacing frequency depending on the patient's activity.