Inner Catheter Wave Pattern Reduces Friction in Stent Delivery
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Solution Overview
Problem
The precise placement of intraluminal medical devices, such as self-expanding stents, is compromised due to deflection of the delivery system during deployment, caused by frictional forces between the medical device and the outer sheath, leading to unpredictable implantation sites, especially with high frictional loads from devices like drug-coated or long stents.
Innovation Solution
A delivery system featuring an inner catheter with a wave-like pattern and a polymer inner layer adhered to its surface, which minimizes friction with the outer sheath and resists axial compression, preventing buckling and ensuring precise placement of the medical device by maintaining the stent's radial restraint until deployment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the outer sheath is withdrawn during deployment, then the medical device is released and self-expands, but frictional forces between the medical device and outer sheath cause deflection and imprecise placement
Solution Approach 1:
A lubricious coating is applied to the outer surface of the inner catheter to serve as an intermediary layer between the inner catheter and outer sheath. This coating reduces frictional forces during withdrawal, preventing deflection and ensuring precise placement of the medical device at the intended treatment site.
Solution Approach 2:
The inner catheter incorporates a closed coil wire structure with specific geometric parameters (coil diameter, pitch, wire diameter) that provide radial strength to resist compression forces while maintaining flexibility. This structural parameter optimization allows the catheter to withstand frictional loads without buckling or deflecting during deployment.
2Strength
If the inner catheter is made rigid to resist compression, then buckling is prevented, but the delivery system becomes less flexible and harder to navigate
Solution Approach 1:
The inner catheter employs a closed coil wire structure that functions as a flexible shell, providing radial strength and compression resistance while maintaining the flexibility needed for navigation through tortuous vasculature. The coil geometry allows the catheter to bend and conform to vessel contours while resisting axial compression forces.
Solution Approach 2:
The inner catheter combines the closed coil wire structure with a lubricious coating material to create a composite structure that integrates mechanical strength, flexibility, and low-friction surface properties. This composite design achieves both compression resistance and navigational flexibility simultaneously.
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 system reduces frictional forces and maintains structural integrity, allowing for smoother deployment and accurate placement of self-expanding medical devices, minimizing the risk of deflection and ensuring the stent expands correctly against the vessel wall.
Implementation Method 1
minimizes friction with the outer sheath
Implementation Method 2
a polymer inner layer adhered to its surface
Data Source
AI summary
A delivery system for a self-expanding medical device is provided. The delivery system includes an outer sheath that radially restrains the medical device. An inner catheter is disposed within the outer sheath. The inner catheter is a composite structure with an inner layer adhered to the inner diameter of a closed coil wire. The inner catheter has a wave-like pattern along the outer surface that is exposed to the inner surface of the outer sheath.