Multipolar Microlead Twisted Configuration for Implant Navigation
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Solution Overview
Problem
Current implantable medical leads face challenges such as mechanical stress fatigue, stiffness gradients, difficulty in sterilization, and complexity in design, which affect their implantability, mechanical strength, and biostability, particularly due to their size and assembly requirements.
Innovation Solution
A multipolar microlead with a twisted configuration of microcables, each featuring a core cable of multiple strands with a polymer insulation layer and exposed bare core portions forming electrodes, is designed to be flexible, biostable, and compatible with MRI, with a diameter of up to 1.5 French, allowing for reduced size and increased maneuverability in venous, arterial, and lymphatic networks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the lead size is reduced to make it less invasive and easier to handle, then ease of implantation and maneuverability improve, but device complexity increases and technical constraints generate risks
Solution Approach 1:
The lead is divided into multiple independent microcables (typically 3-6 microcables) twisted together to form the complete lead structure. Each microcable contains its own conductor core and insulation layer, allowing the lead to achieve flexibility and maneuverability through the twisting configuration while maintaining structural integrity and reducing overall complexity of each individual component.
Solution Approach 2:
Each microcable is covered with a thin polymer insulation layer that provides flexibility and softness, enabling the lead to navigate tortuous vessel paths. The insulation layer acts as a flexible shell that protects the conductor while allowing the microcable to bend and conform to vessel geometry, thus improving ease of implantation without compromising structural strength.
2Adaptability or versatility
If complex assemblies with multiple parts and wires are used to meet lead requirements, then functional performance is achieved, but mechanical stress fatigue and breakage risk increase
Solution Approach 1:
Multiple functional requirements are merged into each microcable: the conductor core provides electrical conductivity, the polymer insulation provides flexibility and biocompatibility, and the twisted configuration of multiple microcables provides both mechanical strength and flexibility. This merging reduces the number of separate components and assembly steps, thereby reducing fatigue risks from repeated assembly and disassembly operations.
Solution Approach 2:
The lead employs composite material structures: each microcable combines conductive material (for electrical function) with polymer insulation material (for mechanical flexibility and biocompatibility). The twisted assembly of multiple such composite microcables creates a composite structure at the macro level that achieves both electrical performance and mechanical reliability, reducing breakage risk while maintaining functional versatility.
3Ease of operation
If stiffness gradients are introduced to affect implantability properties, then ease of navigation improves, but mechanical strength and fatigue resistance deteriorate
Solution Approach 1:
The lead achieves navigation flexibility through the local quality of its twisted microcable configuration, where the twisting provides natural flexibility and conformability to vessel paths. However, the material composition and cross-sectional structure are designed to maintain uniform strength characteristics throughout, avoiding weak zones that would result from stiffness gradients. The flexibility comes from the geometric arrangement rather than material property gradients, preserving mechanical strength.
4Strength
If transition zones and rigid connections are used to connect microcables, then structural integrity is achieved, but fatigue risks and sterilization difficulties increase
Solution Approach 1:
The microcables are connected through a twisting configuration that merges them into a unified composite structure. The twisting creates friction and interlocking between microcables, providing structural integrity without requiring separate transition zones or rigid connectors. This direct twisting connection eliminates weak interface zones that would be prone to fatigue, while the continuous twisted structure allows for effective sterilization without accessing difficult-to-reach connection points.
Data Source
AI summary
Leads for use with implantable medical devices may be implanted in the venous, arterial, or lymphatic networks. The diameter of a microlead may be at most equal to 1.5 French (0.5 mm), and it may include a plurality of micro-cables each including: an electrically conductive core cable for connection to one pole of a multipolar generator of an active implantable medical device, and a polymer insulation layer surrounding the core cable. At least one exposed area may be formed in the insulation layer to form a detection/stimulation electrode.