Steerable Catheter Skeleton with Metal Support for Kink Resistance
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Solution Overview
Problem
Current steerable cardiac catheters face challenges in navigating complex cardiac anatomy due to large device diameters and kinking issues, requiring increased actuation forces and thicker walls to resist kinking, which complicates access to hard-to-reach areas like the aortic and mitral valves.
Innovation Solution
A steerable catheter design featuring a hollow tube with a metal support structure that allows movement in defined directions, providing enhanced kink resistance and axial stiffness, while minimizing axial compression and wall thickness, using a cut metal tube or skeleton with hinges that allows bending in multiple directions without relying on a composite polymer structure for axial loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the matrix material is softened to reduce actuation forces, then the load required to deflect the section is reduced, but the deflection section becomes more prone to kinking and axial shrinkage
Solution Approach 1:
The patent employs a composite structure combining a softer polymer matrix material with an embedded metal wire braid reinforcement. The polymer matrix (e.g., polyurethane or polyester) provides flexibility and reduces actuation forces, while the metal wire braid (e.g., stainless steel or nitinol) embedded within it provides kink resistance and structural integrity. This composite approach allows the deflection section to remain soft and steerable while preventing kinking and axial compression.
2Reliability
If the matrix material is hardened to increase kink resistance, then the deflection section is less prone to kinking, but higher actuation forces are required and the sheath wall thickness increases
Solution Approach 1:
The patent uses a composite construction where a metal wire braid reinforcement is embedded within a polymer matrix. The metal braid provides the necessary kink resistance and radial strength, allowing the polymer matrix to remain relatively soft and flexible. This eliminates the need to harden the matrix material itself, thereby maintaining low actuation forces while achieving adequate kink resistance.
3Reliability
If the sheath wall thickness is increased to resist kinking and axial compression, then kink resistance improves, but the device diameter increases and available space is reduced
Solution Approach 1:
The patent employs a composite structure with a metal wire braid reinforcement embedded in a polymer matrix. The metal braid provides high radial strength and kink resistance with minimal thickness, allowing the overall sheath wall to remain thin while maintaining structural integrity. This composite approach achieves superior kink resistance without increasing the device diameter or reducing the lumen space.
4Strength
If the density of reinforcement material is increased to improve axial strength, then axial compression resistance improves, but wall thickness increases and actuation forces increase
Solution Approach 1:
The patent uses a metal wire braid reinforcement embedded within a polymer matrix, creating a composite structure where the metal wires provide axial and radial strength. The braid configuration and material selection (e.g., stainless steel or nitinol) provide high strength-to-weight ratio, achieving adequate axial compression resistance without requiring thick walls or high actuation forces.
Data Source
AI summary
A tube or skeleton for a steerable catheter includes a cylindrical body structured to permit bending in at least one bending direction and to resist bending in directions transverse to the bending direction. The cylindrical body may include a laser cut metal tube, wires bent and connected to one another, or one or more coiled wires with axial support wires attached to the coil to define one or more bending directions to form bending segments. The skeleton includes axially stiff portions that resist compression when a pull wire is pulled to cause bending movement. The axially stiff portions may include a backbone, an alignment of pivot structures, connected axially extending portions of wire elements, or axially extending support wires or rods. Two or more bending portions may be provided, each with different bending directions. Complex bending shapes may be provided by arranging the segments in rotated positions along the skeleton.