Acoustic Pacemaker Transmitter Waveform Shaping
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Solution Overview
Problem
Conventional pacemaker systems face challenges in optimizing energy efficiency and reducing the size of the implanted device while minimizing electrode polarization and effectively sensing evoked electrograms post-stimulation.
Innovation Solution
An acoustic pacemaker system that uses an implanted or external transmitter to deliver pacing energy wirelessly to a receiver-stimulator, with controlled acoustic waveforms that compensate for tissue-electrode impedance, reducing after-potentials and enhancing energy efficiency by modifying the pacing pulse shape and reducing the size of the implanted controller-transmitter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrical pacing pulses are applied through lead wires and electrodes, then cardiac tissue can be stimulated effectively, but electrode polarization occurs causing after-potentials that inhibit detection of evoked responses
Solution Approach 1:
The patent replaces the conventional electrical stimulation system with an acoustic stimulation system. An external acoustic transmitter generates ultrasonic waves that pass through the chest wall to stimulate the heart acoustically, eliminating the need for implanted electrodes and lead wires. This substitution of acoustic energy for electrical energy through tissue resolves the electrode polarization problem entirely, as no electrode-tissue interface is involved in the stimulation process.
2Reliability
If pacing pulse amplitude and duration are increased to ensure reliable cardiac stimulation, then stimulation effectiveness improves, but energy consumption increases reducing battery life
Solution Approach 1:
The patent replaces the battery-powered electrical pulse generator with an external acoustic transmitter that does not require implantation. The external device can be recharged or replaced easily, eliminating the constraint of internal battery life. The acoustic energy transmission through tissue is highly efficient, and the system can deliver adequate stimulation energy without the energy storage limitations of an implanted battery.
3Volume of moving object
If the implanted device size is reduced to minimize surgical trauma and improve patient comfort, then implantability improves, but energy storage capacity and sensing capabilities are compromised
Solution Approach 1:
The patent extracts the energy generation and acoustic transmission functions from the implanted device and places them in an external transmitter. The implanted receiver-stimulator contains only the essential components for receiving acoustic energy, converting it to electrical signals, and stimulating the heart, resulting in a dramatically smaller implant. The external transmitter handles the energy-intensive functions, so its size does not constrain the implant.
4Shape
If acoustic transmission waveform amplitude is increased to compensate for tissue-electrode impedance, then pacing pulse shape improves, but energy loss in the acoustic field increases
Solution Approach 1:
The patent modifies the acoustic transmission waveform parameters, specifically using a decaying envelope rather than a constant amplitude waveform. This parameter change allows the system to deliver adequate stimulation while reducing the peak acoustic energy required. The decaying envelope shape matches the impedance characteristics of the tissue-acoustic interface, improving energy transfer efficiency and reducing acoustic energy loss.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system achieves improved energy efficiency, reduced size of the implanted device, and enhanced sensing capabilities by generating optimal pacing waveforms that compensate for tissue-electrode impedance, leading to longer battery life and smaller battery capacity requirements.
Implementation Method 1
The implanted receiver-stimulator device comprises a piezoelectric sensor component, which passes an alternating current signal representing the acoustic field impinging upon it
Data Source
AI summary
A system for delivering an electrical stimulation pulse to tissue comprises a controller-transmitter and a receiver-stimulator. The controller-transmitter includes circuitry having an energy storage capacitor. The capacitance of the energy storage capacitor is adjusted to improve the efficiency of energy delivered from the receiver-stimulator to tissue by modifying the geometry of an acoustic drive burst from the controller-transmitter.