Stent Delivery Sheath with Elastic Outer Layer and Separation Lines
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Solution Overview
Problem
Existing stent delivery systems face challenges in providing an atraumatic and dilating surface for self-expanding stents, especially in smaller vessels and curved sections, where a distal tip may not be feasible, and materials with low friction often lack elasticity, leading to risks of stent misalignment and vascular damage.
Innovation Solution
A delivery sheath with a distal portion comprising a radially inner layer of low friction material and an outer elastic layer, featuring longitudinal separation lines that allow circumferential movement of leaf edges to accommodate radial expansion, providing an atraumatic surface during delivery and facilitating safe retraction over the stent without catching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a distal tip is provided on the inner core to provide an atraumatic surface, then the stent can be advanced safely through the vasculature, but it becomes impossible or inconvenient to use with stents of smaller radius or longer stents over curved sections
Solution Approach 1:
Instead of providing the atraumatic surface on the inner core as a rigid distal tip, the invention inverts the approach by providing the atraumatic surface on the sheath itself. The sheath's distal end is formed of elastic material that can be resiliently deformed radially outwardly to accommodate the stent but forwardly of the stent relaxes to a narrower diameter, creating an atraumatic surface that is less than the diameter of the stent and approaches the outside diameter of the wire guide.
Solution Approach 2:
The sheath distal end is designed with variable diameter along its length, tapering from a larger diameter at the stent interface to a smaller diameter forwardly of the stent. This parameter change creates the atraumatic surface while maintaining the ability to accommodate the stent during delivery.
2Adaptability or versatility
If the sheath distal end is made entirely of elastic material to accommodate stent expansion, then the sheath can stretch to allow stent deployment, but the friction against the stent increases causing catching during retraction
Solution Approach 1:
The sheath is divided into distinct functional segments: a distal end portion made of elastic material for accommodating stent expansion, and an inner core with low friction material for smooth retraction. The separation line longitudinally divides the sheath structure, allowing each segment to perform its specific function independently.
Solution Approach 2:
Different portions of the sheath are assigned different material properties according to their specific functions. The distal end has high elasticity to accommodate stent expansion, while the inner core has low friction properties to enable smooth retraction. This local differentiation of material qualities optimizes performance in each region.
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
The solution reduces the risk of stent misalignment and vascular damage by ensuring smooth retraction of the sheath over the stent, even in curved sections, while maintaining low friction and elasticity, thus enhancing the safety and efficacy of stent deployment.
Implementation Method 1
the radially inner layer comprises a material having a low coefficient of friction
Implementation Method 2
the radially outer layer comprises an elastic material; which can be resiliently deformed radially outwardly to accommodate the stent
Data Source
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AI summary
A stent delivery sheath (104) has a distal portion extending circumferentially around a stent (102), the delivery sheath tapering distally of the stent to a reduced diameter at the distal end of the sheath (110) so providing an atraumatic or dilating surface distally of the stent. The distal portion of the delivery sheath comprises a low friction inner layer (106) and an elastic outer layer (108) both extending to the distal end of the sheath. The inner layer has at least one separation line (112) extending longitudinally of the sheath to the distal end to define at least two leaf edges in the radially inner layer which are configured to move circumferentially with respect to each other to accommodate elastic radial expansion of the outer layer as the sheath is retracted proximally with respect to the stent.