Shape Memory Vena Cava Filter Anchoring
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Solution Overview
Problem
Existing vena cava filters face challenges in maintaining position without causing undue damage to the vessel wall and preventing tissue growth that complicates removal, while also needing to be self-orienting and resistant to migration forces.
Innovation Solution
A vessel-implantable filter made of shape memory material that transitions between austenitic and martensite states, using oppositely disposed extension elements to maintain position and facilitate easy removal by straightening hooks when withdrawal force is applied, reducing the risk of vessel wall injury.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If hooks are used to penetrate the vessel wall to prevent migration, then the filter's stability against migration forces is improved, but the risk of vessel wall injury increases
Solution Approach 1:
The patent changes the physical state of the shape memory material between martensite (soft, flexible for insertion) and austenite (rigid, stable for anchoring) phases. This parameter change allows the hooks to be inserted easily in martensite state and then locked in place when transforming to austenite state, providing stability without excessive penetration force
Solution Approach 2:
The filter system transitions from a static anchoring mechanism to a dynamic one using shape memory material that can reversibly change its mechanical properties. The material dynamically adapts between soft/compliant during insertion and hard/rigid during stabilization, reducing vessel wall injury while maintaining filter stability
2Ease of operation
If the filter is made retrievable with hooks that can be straightened, then ease of removal is improved, but the filter's resistance to migration forces during normal operation may be compromised
Solution Approach 1:
The shape memory material's phase transition capability allows the hooks to exhibit high rigidity in austenite state for migration resistance during normal operation, and transform to martensite state for easy retrieval. The same material structure provides both stability and removability through parameter change
Solution Approach 2:
The filter operates in two distinct periodic phases: during normal operation the material maintains austenite phase for stability, and during retrieval it transforms to martensite phase for easy removal. This periodic switching between functional states resolves the contradiction between stability and ease of removal
3Stability of the object's composition
If extension elements are used to anchor the filter, then migration prevention is improved, but tissue growth around the anchors complicates removal
Solution Approach 1:
The shape memory material allows the extension element hooks to transform from austenite to martensite phase, changing from a tissue-integrated state to a flexible retrieval state. This parameter change enables removal after tissue growth has occurred without being impeded by the tissue integration
Solution Approach 2:
The anchoring mechanism transitions from a static, tissue-integrated anchor to a dynamic, retrievable structure. The shape memory material enables the hooks to adapt their mechanical properties over time, allowing initial stable anchoring followed by facilitated removal even after tissue growth
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 filter effectively maintains position within the vena cava without causing significant damage and can be easily removed without harming the vessel wall, while providing stability against migration forces, including those from respiratory functions or embolisms.
Implementation Method 1
A vessel-implantable filter made of shape memory material that transitions between austenitic and martensite states
Implementation Method 2
shape memory material with temperature induced austenitic and martensite states which may be easily removed by a single removal device after an extended period of time without significantly injuring the vessel wall
Data Source
AI summary
A filter having a first set of members and a second set of members defining a trap sized to fit into a blood vessel. Each of the first and second members are configured to resiliently extend from the trap. At least one of the first set of members includes a first surface for engaging the vessel wall such that the at least one of the first set of members resists downstream movement within the vessel. At least one of the second set of members includes a second surface for engaging the vessel wall such that the at least one second member resists upstream movement within the vessel.