Foldable Stent Section for Repositioning
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Solution Overview
Problem
Conventional collapsible prosthetic heart valve stent designs face challenges in repositioning during placement due to high forces required for delivery sheath retraction and are prone to cuff and leaflet failure during compression and expansion.
Innovation Solution
A stent design with a foldable section, annulus section, and aortic section arranged in series, featuring cells with different angles to allow for controlled elongation, facilitating easy compression and repositioning while minimizing damage to the valve assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the stent frame is constructed with cells defining acute angles at the longitudinal ends, then the stent can be compressed for delivery, but high forces are required to slide the delivery sheath back over the partially deployed stent making repositioning difficult
Solution Approach 1:
The stent frame is divided into three distinct sections with different cell angle configurations: an aortic section with acute angles for compression, an annulus section with substantially equal angles for structural support, and a transition section with gradually changing angles. This segmentation allows each section to perform its specific function optimally while working together as a unified structure.
Solution Approach 2:
Different sections of the stent frame are given different local geometric properties. The aortic section has acute angles optimized for compression, the annulus section has substantially equal angles optimized for radial strength and positioning stability, and the transition section has gradually changing angles to bridge the two configurations. This local quality differentiation resolves the contradiction by providing the right geometric properties in the right locations.
2Ease of operation
If the stent frame is constructed with cells defining substantially equal angles or obtuse angles at the longitudinal ends, then repositioning may be easier, but the large amount of elongation during crimping causes the cuff and leaflet material to fail
Solution Approach 1:
The valve assembly is positioned specifically within the annulus section which has substantially equal angles, while the aortic section with acute angles handles the compression mechanics. This spatial segmentation protects the valve components from the high elongation stresses that would occur if they were positioned in the acute-angle section during crimping.
Solution Approach 2:
The stent is pre-configured with the valve assembly attached to the annulus section before delivery. The annulus section's substantially equal angle geometry is designed in advance to minimize elongation during crimping, thereby preventing cuff and leaflet failure before the device even enters the delivery system.
3Device complexity
If a single-layer stent design is used, then the structure is simpler, but it cannot simultaneously provide easy compression for delivery and maintain structural integrity to prevent valve assembly damage
Solution Approach 1:
The stent is divided into three functional sections with progressively different cell angle configurations, creating a multi-functional structure from a single continuous frame. This segmentation allows the device to achieve multiple objectives (compression ease, structural integrity, valve protection) that would be impossible in a uniform single-layer design.
Solution Approach 2:
The cell angle parameter is systematically varied along the length of the stent frame, transitioning from acute angles in the aortic section to substantially equal angles in the annulus section. This parameter change allows the stent to optimize its mechanical properties for different functional requirements at different locations, achieving both ease of compression and structural integrity.
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 design enables safe repositioning of the prosthetic heart valve by allowing controlled elongation, reducing the risk of valve assembly damage during compression and expansion, thus improving implantation efficacy.
Implementation Method 1
a stent including a foldable section, an annulus section, and an aortic section arranged in series, the stent being movable between an unfolded condition in which the foldable section is spaced from the annulus section in a longitudinal direction, and a folded condition in which the foldable section is at least partially positioned within the annulus section
Data Source
AI summary
A collapsible prosthetic heart valve includes a stent and a valve assembly. The stent includes an annulus section and at least one foldable section. The stent is movable between an unfolded condition in which the foldable section is longitudinally spaced from the annulus section, and a folded condition in which the foldable section is at least partially positioned radially adjacent the annulus section. The valve assembly is positioned within the annulus section of the stent in the folded condition of the stent.