Retaining Cage for TAVI Valve Resheathing and Repositioning
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Solution Overview
Problem
Conventional delivery systems for self-expanding prosthetic heart valves face challenges in controlling partial deployment, repositioning, and assessing valve function without full deployment, leading to increased procedural length and risk of tissue damage due to anatomical variations and the inability to resheath the valve once fully expanded.
Innovation Solution
A medical device implantation system featuring a shaft, expandable stent, slidable sheath, and a retaining cage with shape-memory alloy fingers that allows for partial deployment and repositioning of the valve by retracting the sheath, enabling the valve to be collapsed and repositioned within the patient, and a method for delivering the valve using a system with a handle and distal cap for independent actuation of the shaft and sheath.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a self-expanding valve is fully deployed, then the valve expands to full operating size, but the valve diameter becomes larger than the sheath, making resheathing impossible
Solution Approach 1:
The delivery system is divided into separate components: a sheath for delivering the collapsed valve, a deployment mechanism for expanding the valve, and a retention structure that allows the valve to be held in a collapsed state even after partial expansion. This segmentation enables independent control of delivery, deployment, and retention functions.
Solution Approach 2:
The system transitions from a static sheath-based retention mechanism to a dynamic retention mechanism where the valve can be held in various states (collapsed, partially expanded, fully expanded) through active control of the deployment mechanism. The retention structure can adaptively hold the valve in different configurations based on procedural needs.
2Ease of operation
If a valve is partially deployed to enable resheathing, then the valve remains in sheath, but the user's ability to test valve function and fitment is limited
Solution Approach 1:
The system allows for controlled partial deployment where the valve can be expanded to the extent needed for functional assessment while remaining retainable. The deployment mechanism enables incremental expansion, allowing the operator to stop at any intermediate stage and still maintain the ability to resheath if needed.
Solution Approach 2:
The system changes the retention parameter from binary (retained/not retained based on full collapse) to continuous (retainable at various expansion states). The retention structure maintains grip on the valve even when partially expanded, allowing functional testing while preserving the option to resheath.
3Productivity
If conventional delivery devices are used, then the valve can be delivered and deployed, but it is difficult to control how much of the valve remains in the sheath during partial deployment
Solution Approach 1:
A dedicated retention structure acts as an intermediary between the sheath and the valve, providing controlled engagement and release mechanisms. This intermediary component mediates the interaction between the delivery system and the valve, enabling precise control over deployment extent without requiring complex multi-component control systems.
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 precise control over the deployment and repositioning of self-expanding prosthetic heart valves, allowing for functional assessment and potential repositioning or removal without causing trauma, thereby reducing procedural risks and improving anatomical fitment.
Implementation Method 1
a retaining cage with shape-memory alloy fingers that allows for partial deployment and repositioning of the valve
Data Source
AI summary
A delivery device for an implantable medical device includes an inner shaft extending in a longitudinal direction and an outer shaft surrounding at least a longitudinal portion of the inner shaft. The outer shaft is slidable relative to the inner shaft in the longitudinal direction. A sheath surrounds a longitudinal portion of the outer shaft, the sheath having an outer diameter and being slidable in the longitudinal direction between a first position enclosing the medical device and a second position exposing the medical device to permit full functionality of the medical device. A retaining cage is coupled to the outer shaft, the retaining cage being configured and arrange to collapse the medical device during resheathing.