Rupturable Sheath for Self-Expanding Stent Delivery
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Solution Overview
Problem
The deployment of self-expanding stents in vessels is complicated by axial loading forces and friction, particularly with polymer-coated drug-eluting stents and nitinol stents, which can lead to thromboembolic complications due to dislodged plaque fragments passing through open stent structures during balloon expansion and removal of the delivery sheath.
Innovation Solution
A self-expanding stent-sheath combination where the sheath is constructed with a region of compromised structural integrity, such as scored or fused regions, that ruptures during stent expansion, allowing for reduced axial loading forces and friction, and facilitating the removal of the sheath after deployment, thereby minimizing the risk of plaque dislodgment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a self-expanding stent is delivered through a sheath using axial loading forces, then the stent can be positioned at the desired location, but friction between the stent and sheath increases the risk of plaque dislodgment and thromboembolic complications
Solution Approach 1:
A lubricant coating is applied to the sheath surface to reduce friction between the stent and sheath during delivery. This intermediary substance allows the stent to be advanced with minimal axial loading forces, reducing the risk of plaque dislodgment while maintaining delivery control and placement accuracy.
2Stability of the object's composition
If the sheath is made intact to contain the stent during delivery, then the stent remains constrained, but the sheath cannot rupture to allow free expansion, increasing residual stress
Solution Approach 1:
The sheath is designed with differentiated structural properties: the distal portion contains circumferential weaknesses (scores or notches) that allow controlled rupture during expansion, while the proximal portion remains intact to maintain containment and provide pushability during delivery. This local quality variation allows the sheath to serve dual functions of constraint and controlled release.
3Ease of operation
If axial loading forces are applied to deliver the stent, then the stent can be pushed through the vessel, but friction generates heat and increases plaque dislodgment risk
Solution Approach 1:
A lubricant coating is applied to the sheath surface to reduce friction between the stent and sheath during delivery. This intermediary substance allows the stent to be advanced with minimal axial loading forces, reducing the risk of plaque dislodgment while maintaining delivery control and placement accuracy.
4Stress or pressure
If the sheath is designed to rupture during expansion, then the stent can expand freely, but the sheath may fragment and remain in the vessel
Solution Approach 1:
The sheath is designed with differentiated structural properties: the distal portion contains circumferential weaknesses (scores or notches) that allow controlled rupture during expansion, while the proximal portion remains intact to maintain containment and provide pushability during delivery. This local quality variation allows the sheath to serve dual functions of constraint and controlled release.
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 solution reduces axial loading forces and friction during stent deployment, enhances accuracy of balloon expansion, and minimizes the risk of thromboembolic complications by allowing the stent to expand freely while removing the sheath, ensuring accurate placement and reduced risk of plaque dislodgment.
Implementation Method 1
a self-expanding nitinol stent may be of the kind that expands when warmed above the martensitic transition temperature for the nitinol alloy (e.g., above 30° C.)
Implementation Method 2
other stents, such as the Palmaz Blue® stent, are expanded radially outward by the force imparted by an inflated angioplasty type balloon as the balloon pushes against the inner stent walls
Implementation Method 3
a self-expanding stent possesses a spring force that causes the stent to expand following its implacement in the artery when a restraining sheath is retracted from the compressed stent
Data Source
Figure 1~3
Figure 4~5
AI summary
The present disclosure is directed to self-expanding stent (20) encased within a fused film (30) in which the film is rupturable upon deployment of the stent, by means of a balloon (90) catheter or the like. In one embodiment a stent assembly comprises a crimped self-expanding stent wrapped within a fused film. The film is provided with a rupturable region (40) of compromised structural integrity. A portion of the film may be fused to the distal end of a stent delivery system.