Variable Wall Thickness Sheath for Catheter Trackability
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Solution Overview
Problem
Sheaths and catheters used in endoluminal procedures require a balance between longitudinal strength and flexibility to navigate curved vasculature without kinking, but existing strengthening elements often compromise flexibility and trackability, and can increase diameter, making deployment challenging.
Innovation Solution
A sheath design with a proximal section having a smaller diameter and a distal section with a thinner wall, featuring a transition zone to reduce kinking risk and enhance flexibility, along with a pusher element providing radial support to prevent device slippage, ensuring smooth deployment and increased trackability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If strengthening elements such as coils or metal braids are embedded in the sheath to reduce kinking risk, then longitudinal strength and kink resistance are improved, but flexibility and trackability are worsened
Solution Approach 1:
The sheath is divided into multiple sections with different wall thicknesses: a proximal section with greater wall thickness for strength, a distal section with reduced wall thickness for flexibility, and a transition section with gradually varying wall thickness. This segmentation allows each section to be optimized for its specific function without compromising overall performance.
Solution Approach 2:
Different sections of the sheath have different wall thicknesses tailored to their specific functional requirements. The proximal section has thicker walls for structural support and kink resistance, while the distal section has thinner walls for enhanced flexibility and trackability in curved vasculature. This local differentiation resolves the contradiction by providing strength where needed and flexibility where required.
2Strength
If strengthening elements are extended substantially for the whole length of the sheath to minimize kinking, then kink resistance is improved, but sheath diameter is increased particularly at the distal end
Solution Approach 1:
The strengthening structure is segmented rather than continuous. It is concentrated in the proximal section where kink resistance is most critical, while the distal section has reduced or no strengthening elements, allowing for a smaller diameter that facilitates deployment through narrow vasculature.
Solution Approach 2:
The strengthening elements are distributed non-uniformly along the sheath length, with higher concentration in the proximal section and reduced presence in the distal section. This local differentiation provides kink resistance where needed while maintaining a small diameter for顺利通过 narrow vessels.
3Adaptability or versatility
If the sheath has a smaller distal wall thickness to improve flexibility, then trackability is improved, but longitudinal strength is reduced
Solution Approach 1:
The sheath is segmented into proximal, transition, and distal sections with progressively varying wall thicknesses. The proximal section has thick walls for strength, the distal section has thin walls for flexibility, and the transition section provides a gradual intermediate transition, preventing stress concentration and kinking at the transition zone.
Solution Approach 2:
Each section of the sheath has wall thickness locally optimized for its function: the proximal section prioritizes longitudinal strength with thicker walls, while the distal section prioritizes flexibility with thinner walls. The transition section balances both requirements with gradually varying thickness.
Data Source
AI summary
An introducer assembly (10) includes a sheath (18) having a proximal portion (26) with a greater wall thickness and a distal portion (30) with a smaller wall thickness. A transition portion (28) may be provided to give a gradual transition between the proximal and distal portions (26, 30). The outer surface (32) of the sheath (18) has a substantially smooth and preferably even form and preferably constant diameter. The sheath (18) can thus have a greater flexibility at its distal end that at its proximal end, to improve trackability and thus to facilitate deployment of an implantable medical device (16) carried by the introducer (10). The smooth outer surface (22) prevents snagging of the introducer assembly (10) during and after the deployment procedure.