Implantable Lead Conductive Inner Surface Reduces Motion Artifacts
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Solution Overview
Problem
Piezoelectric sensors used in implantable medical devices to monitor heart activity are affected by motion artifacts, making it difficult to distinguish between useful signals and noise, especially in environments with significant patient or heart motion.
Innovation Solution
An implantable cardiac lead with a non-conductive polymeric tube and a conductive inner surface layer to prevent electrical charge accumulation, reducing motion artifact interference by ensuring no direct contact between conductors and insulating portions of the tube, thereby isolating the sensor signal from motion-induced noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a piezoelectric sensor is used to detect pressure changes in the heart, then the sensor can provide voltage changes corresponding to pressure changes, but motion artifacts from patient or heart motion create large voltage changes that disturb the sensor signal and make interpretation difficult
Solution Approach 1:
A conductive layer is introduced as an intermediary between the piezoelectric sensor and the insulating polymeric tube. This conductive layer serves as a mediator that prevents charge accumulation at the interface between the sensor and tube, thereby eliminating motion artifacts while preserving the sensor's ability to detect pressure changes
Solution Approach 2:
The invention converts the potentially harmful effect of motion-induced charge accumulation into a beneficial solution by applying a conductive layer that allows charges to dissipate. The same motion that previously caused artifacts now operates in an environment where charges are continuously neutralized, turning the problem of charge accumulation into an opportunity to implement a charge-dissipating interface
2Reliability
If a non-conductive polymeric tube is used to insulate the conductor, then electrical insulation is provided, but electrical charges accumulate between the conductor and the tube, creating motion artifacts
Solution Approach 1:
The solution applies local quality by differentiating the electrical properties at different locations: the bulk polymeric tube remains non-conductive to provide insulation, while the inner surface layer is made conductive to prevent charge accumulation. This localized change in electrical conductivity resolves the contradiction between needing insulation and avoiding charge accumulation
3Device complexity
If the conductor directly contacts the insulating tube, then simple construction is achieved, but charge accumulation occurs during motion, distorting the sensor signal
Solution Approach 1:
The conductive layer is applied only to the inner surface of the polymeric tube where it contacts the conductor, rather than making the entire tube conductive. This localized application maintains the insulating properties of the tube bulk while eliminating charge accumulation at the conductor interface, resolving the contradiction between construction simplicity and signal accuracy
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 solution significantly reduces the impact of motion artifacts on sensor signals, allowing for clearer interpretation of heart activity measurements by maintaining a constant voltage and isolating charge contributions from the sensor, enhancing the accuracy of heart monitoring.
Implementation Method 1
the first polymeric tube is provided with a conductive inner surface layer, so as to prevent accumulation of electrical charges between said first conductor and said first polymeric tube
Implementation Method 2
piezoelectric sensors are arranged to alter the mechanical stress of the piezoelectric material in response to a change of loads emanating from for instance an acceleration of a seismic mass or from a change in pressure acting on the sensor. This results in a transport of electrons or electrical charges within the material, which provides a change in voltage across the piezoelectric sensor
Data Source
AI summary
An implantable lead for sensing mechanical activity of a human heart has an insulating polymeric tube extending from a proximal end to a distal end of the lead, an electrical conductor provided in the lumen of the polymeric tube, and a sensor connected to the conductor at the distal end thereof. The polymeric tube is provided with a conductive surface layer along the inner face between the polymeric tube and the electrical conductor, the conductive surface layer being in electrical contact with this conductor. Accumulation of electrical charges between the electric conductor and the polymeric tube is thereby prevented.