Nosecone Design for Reducing Push Force in Heart Valve Delivery
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Solution Overview
Problem
Existing expandable introducer sheaths increase the force required to advance delivery apparatuses, such as stent-mounted prosthetic heart valves, through the sheath, leading to longer procedure times and increased risk of vessel damage.
Innovation Solution
A delivery system comprising an elongate catheter with a capsule containing a crimped stent-mounted heart valve and a nosecone with a tapered distal end and a proximal end with a larger diameter than the capsule, which reduces the average peak push force by increasing the sheath's compliance and reducing friction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a conventional introducer sheath is used, then the sheath structure is simple, but the push force required to advance the delivery apparatus is high
Solution Approach 1:
The sheath is designed to be dynamically expandable and collapsible. During delivery, the sheath expands radially to create a larger lumen diameter, reducing friction and push force. After delivery, it collapses to a smaller diameter for easy removal. This dynamic structural change allows the sheath to adapt its properties based on operational needs, resolving the contradiction between maintaining simple structure and reducing push force.
Solution Approach 2:
The sheath's radial dimensions are changed through expansion and collapse mechanisms. By increasing the radial diameter during delivery, the sheath reduces the contact area and friction between the delivery apparatus and sheath wall, thereby reducing push force. This parameter change (diameter expansion) directly addresses the force reduction goal while maintaining structural simplicity through controlled dimensional variation.
2Productivity
If multiple dilators or sheaths are used to dilate the vessel, then the vessel access is achieved, but the procedure time increases
Solution Approach 1:
The expandable sheath is pre-configured with a collapsible structure that can be rapidly expanded to the required diameter before vessel insertion. This preliminary preparation eliminates the need for multiple sequential dilators, as the sheath can immediately provide the necessary lumen size when expanded, thereby reducing procedure time while maintaining ease of vessel access.
Solution Approach 2:
The sheath is divided into expandable and collapsible segments that can be independently controlled. This segmentation allows the sheath to be compressed to a small profile for insertion through the hemostatic valve, then rapidly expanded to a larger diameter for vessel access, eliminating the need for multiple dilators and reducing procedure time.
3Reliability
If the delivery apparatus is advanced through the sheath, then the implant can be delivered, but the risk of vessel damage increases
Solution Approach 1:
The dynamically expandable sheath reduces push force during delivery by increasing its radial diameter, which decreases the contact pressure between the delivery apparatus and sheath wall. This dynamic adjustment protects the vessel from damage by minimizing mechanical stress during the high-force delivery phase, while maintaining reliability through controlled expansion and collapse.
Solution Approach 2:
The expandable sheath structure provides a cushioning effect by expanding radially before the delivery apparatus encounters high resistance. This expansion creates a larger, more compliant lumen that reduces friction and peak forces during advancement, thereby cushioning the vessel from damage while still allowing effective delivery of the implant.
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 delivery system effectively reduces the average peak push force required to advance the stent-mounted heart valve through the introducer sheath, enhancing procedural efficiency and minimizing the risk of vessel damage, with peak push forces often below 33 Newtons.
Implementation Method 1
reduces the average peak push force by increasing the sheath's compliance and reducing friction
Data Source
AI summary
A delivery system for delivering a stent-mounted heart valve, or other implant, through an introducer sheath. The delivery system includes an elongate catheter supporting a capsule. The capsule contains the stent-mounted heart valve in the crimped condition. The capsule includes a protrusion extending from its outer surface for urging the sheath away from the outer surface capsule as it moves therethrough, thereby reducing an average peak push force resulting from advancement of the capsule through the sheath.