Non-cylindrical Prosthetic Valve Anchoring via Segmented Nitinol Stent
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Solution Overview
Problem
Existing cardiac valve replacement methods are invasive, require prolonged hospitalization, and face challenges such as migration of prosthetic valves, inadequate anchoring, sealing issues, and complications from irregular and calcified native cardiac rings, often necessitating extracorporeal circulation and heart stopping.
Innovation Solution
A self-expandable prosthetic valve assembly with a tissue valve supported by a stent made of wires, featuring proximal and distal anchors and a central band that adapts to varying anatomies, includes axial wedging portions to secure the valve and ensure sealing, using materials like Nitinol for shape memory and radial restraints to maintain diameter and prevent migration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a cylindrical stent-supported valve is used for transluminal delivery, then minimally invasive implantation is achieved, but migration and inadequate anchoring occur due to inability to adapt to varying anatomies
Solution Approach 1:
The stent is divided into multiple expandable cells that can be independently configured. Each cell acts as a separate unit that can adapt to local anatomical variations, allowing the overall stent to conform to irregular and calcified cardiac rings while maintaining secure anchoring through the segmented structure's ability to distribute forces across multiple contact points.
Solution Approach 2:
The stent transitions from a compressed low-profile state during delivery to an expanded conforming state at the implantation site. This dynamic transformation allows the stent to adapt its shape and diameter to match the native anatomy, ensuring reliable anchoring while maintaining minimally invasive delivery through the vasculature.
2Manufacturing precision
If balloon expansion is used to deploy the stent-supported valve, then positioning is achieved, but trauma to fragile tissue valves occurs
Solution Approach 1:
The stent is designed as a self-expandable structure that uses its own elastic memory to deploy and position the valve. The superelastic Nitinol material naturally returns to its pre-shaped configuration when released, providing controlled expansion without requiring external balloon inflation. This self-service mechanism eliminates balloon-related trauma to fragile tissue valves while maintaining precise positioning through the material's inherent shape memory.
3Reliability
If the stent is made rigid to prevent migration, then anchoring is improved, but adaptability to irregular and calcified cardiac rings is reduced
Solution Approach 1:
The stent employs thin-walled expandable cells made of superelastic Nitinol that provide flexibility while maintaining structural integrity. These thin-film structures can conform to irregular and calcified cardiac rings, adapting to anatomical variations without compromising anchoring stability. The flexible cell walls distribute radial forces evenly, preventing migration while accommodating the irregular geometry of diseased valves.
Solution Approach 2:
The stent combines superelastic Nitinol alloy with a cellular geometric structure to achieve both flexibility and strength. This composite design integrates the material's shape memory properties with the mechanical advantages of the cell geometry, creating a structure that is simultaneously adaptable to irregular anatomies and rigid enough to prevent migration once deployed.
4Reliability
If the stent diameter is fixed to maintain valve geometry, then sealing is improved, but ability to adapt to varying vessel diameters is reduced
Solution Approach 1:
Different portions of the stent are designed with different cell geometries and expansion characteristics. The distal and proximal portions can adapt to varying vessel diameters and anatomical conditions, while the central portion maintains a controlled diameter to ensure proper valve sealing. This local differentiation allows each segment to optimize its function for the specific anatomical requirements at that location.
Solution Approach 2:
The stent's physical parameters, including cell size, wire thickness, and expansion ratio, are varied along its length to achieve different functional zones. By changing these parameters locally, the stent can simultaneously adapt to varying vessel diameters in different regions while maintaining a controlled diameter at the valve seating position to ensure adequate sealing against the cardiac ring.
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
Enables minimally invasive valve replacement with secure anchoring, effective sealing, and controlled diameter maintenance, reducing complications and hospital stay, while allowing blood flow during procedures without extracorporeal circulation.
Implementation Method 1
using materials like Nitinol for shape memory
Data Source
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AI summary
A heart valve prosthesis comprising a non-cylindrical frame wherein the frame comprises an inflow zone (852), an outflow zone (854), and a valve support zone(856) between the inflow zone and the outflow zone. The zones are made of cells and the cells are the largest at the outflow zone, smaller at the inflow zone and smallest at the valve support zone.