Steerable Catheter Flat Pull Wires Torque Transfer
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Solution Overview
Problem
Conventional catheters face challenges in achieving a balance between pushability, torqueability, flexibility, and kink resistance, particularly in smaller diameters, which compromises their performance in navigating tortuous vascular paths during medical procedures.
Innovation Solution
The use of flat pull wires and a braided wire assembly with varying braid density, combined with a melt-processing polymer outer layer, to create a steerable catheter with a reduced outer diameter and enhanced flexibility and control, while maintaining strength and resistance to kinking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional round wires are used as pull wires with embedded lumens, then the catheter structure is simple to manufacture, but the outer dimension of the catheter increases
Solution Approach 1:
The patent applies asymmetry by transitioning from conventional round pull wires to flat pull wires with rectangular cross-sections. This asymmetric shape change allows the catheter to achieve a smaller outer dimension while maintaining the necessary lumen functionality, directly resolving the contradiction between reduced volume and manufacturing simplicity.
2Area of stationary object
If the bore size of the introducer catheter is increased, then the inner diameter is large enough to accommodate the ablation device, but the wall thickness decreases making the catheter more likely to collapse
Solution Approach 1:
The patent employs composite materials by combining flat pull wires made of flexible material with an outer layer comprising melt-processing polymer and a braided wire assembly. This composite structure allows the catheter to maintain a large bore size while the braided wire assembly provides enhanced structural strength and collapse resistance, resolving the contradiction between bore size and wall thickness.
3Strength
If the wall thickness of the introducer catheter is increased to prevent collapse, then the catheter has sufficient torqueability, but the overall diameter increases
Solution Approach 1:
The patent applies local quality by concentrating the torque transmission function in the braided wire assembly layer rather than uniformly increasing wall thickness throughout the catheter structure. This localized reinforcement provides sufficient torqueability while maintaining a smaller overall diameter, resolving the contradiction between strength and volume.
4Adaptability or versatility
If conventional round pull wires are used, then the manufacturing process is straightforward, but the catheter lacks flexibility and steerability in small passages
Solution Approach 1:
The patent applies parameter changes by modifying the cross-sectional geometry of the pull wires from circular to flat rectangular shapes, and by varying the braid density in the braided wire assembly. These parameter changes enhance flexibility and steerability for navigating small passages while maintaining a manageable structural complexity.
5Volume of moving object
If the catheter is made thinner to reduce outer diameter, then the catheter can navigate smaller passages, but the catheter becomes more prone to kinking
Solution Approach 1:
The patent uses composite materials with the braided wire assembly providing kink resistance while the outer layer uses melt-processing polymer for flexibility. This composite construction allows the catheter to maintain a thin outer diameter for navigating small passages while the braided structure prevents kinking, resolving the contradiction between volume and reliability.
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
This design allows for a smaller outer diameter catheter with improved steerability, flexibility, and control, enabling effective navigation through small vascular passages while maintaining sufficient axial strength and torque transmission.
Implementation Method 1
applying sufficient heat to the melt processing polymer to raise the temperature of the polymer above its melting point
Implementation Method 2
a layer of heat shrink material encompassing the outer layer
Data Source
AI summary
A catheter assembly includes an inner liner made of flexible material and an outer layer having a steering mechanism. The steering mechanism includes at least one flat wire and a corresponding lumen through which the flat wire may travel. The steering mechanism may also include at least one pull ring to which the flat wires are attached. A layer of heat shrink material may encompass the outer layer. A braided wire assembly may also be provided in the outer layer, and may be formed by braiding a plurality of flat wires into a wire mesh. The overall cross-section of the catheter assembly is preferably substantially circular. A catheter shaft may include a plurality of segments of differing hardness characteristics. The outer layer typically comprises a melt processing polymer such that the catheter assembly may be laminated using heat.