Implantable Medical Lead Coil Electrode with Inter-turn Polymer
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Solution Overview
Problem
Existing implantable neurological leads require smaller outer diameters and greater flexibility to accommodate various applications, particularly in peripheral nerve stimulation where leads need to be inserted under the skin along flexible body parts, and current designs often lack sufficient stiffness and are prone to inflexibility and fibrotic ingrowth.
Innovation Solution
An implantable medical electrical lead with a flexible elongate tubular body featuring a coil electrode with polymeric material between its turns, allowing for a smaller outer diameter and increased flexibility while maintaining electrical conductivity, and optionally incorporating a lumen for stiffness and drug delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the lead uses traditional cylindrical band electrodes with stiffening members, then column strength is sufficient for delivery, but the lead outer diameter is larger and flexibility is reduced
Solution Approach 1:
The electrode is segmented into multiple discrete coil turns rather than a continuous band, allowing the lead to achieve flexibility while maintaining structural integrity through the distributed coil structure
Solution Approach 2:
The lead combines conductive wire material with polymeric filling material to create a composite structure that provides both electrical conductivity and mechanical flexibility while reducing outer diameter
2Ease of operation
If the lead is made more flexible with smaller diameter, then ease of insertion and patient comfort improve, but column strength during delivery is insufficient
Solution Approach 1:
The polymeric material is pre-filled between the coil turns to provide temporary structural support during delivery, which is later removed or remains as a flexible matrix, enabling the lead to be both insertable and strong
Solution Approach 2:
The lead uses a flexible polymeric matrix structure that can be temporarily stiffened during delivery and then becomes flexible for patient comfort, mimicking the behavior of flexible shells that can transition between rigid and flexible states
3Length of moving object
If the coil inter-turn space is left empty, then the lead outer diameter is smaller, but fibrotic ingrowth occurs around the electrode coil wire
Solution Approach 1:
The polymeric material acts as an intermediary substance filled between the coil turns that prevents direct contact between tissue and the electrode wire, blocking fibrotic ingrowth while maintaining the compact coil structure
Solution Approach 2:
A thin polymeric layer is formed between the coil turns to create a barrier against fibrotic ingrowth, similar to how flexible films can provide protective barriers while maintaining flexibility and compact dimensions
4Reliability
If the polymeric material covers the coil outer surface, then fibrotic ingrowth is prevented, but electrical conductivity with the surrounding environment is lost
Solution Approach 1:
The polymeric material is selectively placed only in the inter-turn spaces rather than covering the entire coil surface, providing local protection against fibrotic ingrowth while leaving the outer surface exposed for electrical conductivity
Solution Approach 2:
The coil structure is segmented with polymeric material filling only the gaps between turns, creating distinct regions where the polymer provides protection internally while the external surface remains conductive
Data Source
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AI summary
Medical electrical leads including coil electrodes having polymeric material between but not over the coil turns. Some leads can be used for neurological sensing and/or stimulation applications. The coil electrodes are more flexible, bendable, and stretchable relative to corresponding cylindrical band electrodes. The polymer fill between the coil turns provides more column strength than coil electrodes having empty space between the coil turns. Some leads have a lumen for receiving stiffening members while others do not have such lumens. An introducer needle can be used to introduce a steerable sheath containing the lead. The sheath and lead can be advanced to near the target site and the sheath removed. The present invention can be used to advantage in peripheral nerve and other applications. Some leads are made by masking the coil electrode outer surface with heat shrink material and filling the coil inter-strand regions with polymer.