Stent Delivery Pull Member with Varying Radial Profile
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Solution Overview
Problem
Stent device delivery systems face challenges with high frictional forces during deployment, leading to material strength issues and potential reliability problems, especially in longer stent devices, where the longer the stent, the greater the friction that must be overcome, and existing solutions either suffer from high deployment force requirements or increased cross-sectional profiles due to material constraints.
Innovation Solution
A stent device delivery system featuring a laminated outer sheath with a polymeric first layer and a reinforcement layer, glued together, which allows for a thin, strong sheath design with a pull member embedded between the layers to distribute force uniformly, and a tapering stent bed profile to reduce deployment force and prevent sticking during retraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pullback outer sheath system is used, then the stent device can be delivered, but high frictional forces must be overcome leading to material strength issues and potential reliability problems
Solution Approach 1:
The outer sheath is divided into multiple functional segments: a distal portion with specific friction characteristics, a proximal portion with different mechanical properties, and a transition portion connecting them. This segmentation allows each segment to be optimized for its specific function, reducing overall deployment forces while maintaining reliability
Solution Approach 2:
Different portions of the outer sheath are given different local qualities - the distal portion has surface characteristics optimized for low friction during pullback, while the proximal portion has enhanced structural strength. The transition portion gradually changes these properties to prevent stress concentrations
2Length of moving object
If the stent device length is increased, then more coverage is provided, but the frictional force increases leading to greater deployment force requirements
Solution Approach 1:
The outer sheath parameters are optimized along its length - surface roughness, thickness, and material composition vary from distal to proximal portions. This gradual parameter change reduces frictional forces along the entire stent length without requiring excessive deployment force
3Force
If a rolling outer sheath system is used, then deployment force is reduced, but the cross-sectional profile increases due to the fold-over portion
Solution Approach 1:
Instead of using a traditional rolling mechanism with a fold-over portion that increases profile, the invention inverts the approach by using a pullback mechanism where the outer sheath is drawn back over a tapered stent bed. This achieves low deployment force without the profile penalty of rolling systems
4Shape
If thinner outer sheath materials are used to reduce profile, then the cross-sectional profile is reduced, but the material strength decreases leading to potential failure
Solution Approach 1:
The outer sheath is constructed as a composite structure with multiple layers having different properties. The distal portion uses thinner material for low profile, while the proximal portion uses thicker or reinforced material for strength. The transition portion combines these characteristics, creating a composite structure that achieves both low profile and sufficient strength
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 provides a reliable and low-profile stent device delivery system that effectively deploys stents with reduced deployment force and increased reliability, using a combination of laminated layers and a tapering stent bed profile to manage friction and force distribution.
Implementation Method 1
a reinforcement layer of polymeric material (or reinforcement plastic layer) that are laminated together. In a preferred embodiment, the first layer and the reinforcement layer are glued together by a glue layer radially between the first layer and the reinforcement layer
Implementation Method 2
a tapering stent bed profile to reduce deployment force and prevent sticking during retraction
Data Source
AI summary
A stent device delivery system and method of making. The stent device delivery system includes a stent device, an outer sheath overlaying the stent device in a radially compact, delivery configuration of the stent device, and a pull member. The outer sheath may include a first layer and a reinforcement layer that are laminated together, a portion of the pull member captured radially between the first layer and the reinforcement layer. At least a partial length of the captured portion of the pull member may be formed with a varying radial profile.