Stent Delivery System with Dual Biasing Members for Repositioning
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Solution Overview
Problem
Conventional stent delivery systems using sheaths face challenges such as difficulty in repositioning, uneven deployment, and high force requirements, which can lead to improper stent placement and mechanical alterations of the stent during compression.
Innovation Solution
A stent delivery system employing an elongate shaft with first and second biasing members to constrain and expand the stent, allowing for precise control and repositioning, using pull wires to apply and release longitudinal tension, enabling central, distal, or proximal expansion and reconstriction of the stent.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional outer sheath/inner catheter delivery device is used to hold and deploy the stent, then the stent can be constrained during delivery, but the device becomes difficult to reposition or remove and slow to operate
Solution Approach 1:
The delivery device employs a dynamic mechanism where the outer sheath can be selectively positioned at different locations along the inner catheter. The sheath is not fixed but can be moved proximally or distally to allow stent recapture or redeployment, transforming a static constraint system into a dynamic one that adapts to procedural needs
Solution Approach 2:
The delivery system is divided into functionally independent segments: the inner catheter that provides structural support, the outer sheath that provides constraint, and the stent itself. This segmentation allows each component to perform its specific function independently while maintaining overall system flexibility for repositioning and removal
2Reliability
If the outer sheath is proximally withdrawn to deploy the stent, then the stent expands, but the physician cannot control the deployment position accurately due to manual retraction difficulties
Solution Approach 1:
The system incorporates visual feedback through radiopaque markers positioned on the delivery device and stent. These markers are visible under fluoroscopy, allowing the physician to monitor the sheath position and stent deployment in real-time, providing feedback that enables precise control of the deployment location
Solution Approach 2:
The manual mechanical retraction of the sheath is supplemented or replaced by a controlled mechanism that allows precise positioning. The system enables the sheath to be held at any position along the catheter and released in a controlled manner, replacing uncontrolled manual jerking with a controlled release mechanism
3Reliability
If the distal portion of the stent is deployed first during sheath retraction, then the stent expands from distal to proximal, but accurate placement of the proximal portion becomes difficult
Solution Approach 1:
The system allows the entire stent to be positioned at the target location before deployment begins. The sheath can be held in place while the stent is precisely positioned using visual markers, ensuring both proximal and distal portions are at the correct location before expansion starts, rather than trying to position the proximal portion after distal expansion
4Manufacturing precision
If direct visualization of the stent is required for accurate placement, then the physician can monitor positioning, but the outer sheath obscures the stent location
Solution Approach 1:
The delivery device incorporates radiopaque markers that appear bright under fluoroscopic imaging. These markers on the sheath and stent provide high-contrast visual indicators that allow the physician to see the stent location and sheath position simultaneously, transforming the obscuring sheath into a visible guide
5Productivity
If a high force is applied to overcome friction between the stent and sheath, then the stent can be delivered, but the introducer catheter may stretch or experience hysteresis
Solution Approach 1:
The system extracts or removes the outer sheath from the stent before the stent enters the high-friction zone of the introducer catheter. By deploying the stent in the larger delivery catheter lumen where friction is lower, and only then passing it through the introducer, the high forces that would stretch or damage the introducer are avoided
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
This system enhances control, accuracy, and ease of stent placement, reducing the risk of malfunction and allowing for smoother, quicker deployment and recapture of the stent, while providing a marker system for precise positioning.
Implementation Method 1
a first biasing member operably connected to the shaft and the stent and a second biasing member operably connected to the shaft and the stent
Implementation Method 2
moving a pull wire operably connected to at least one of the first and the second biasing members and biasing at least one of the first and second biasing members to place longitudinal tension on the stent
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A stent delivery system (10) includes a stent (28) positioned at a stent receiving portion (29) of an elongate shaft (22), the stent having a constrained configuration (40) and an expanded configuration. A first biasing member (52) is operably connected to the shaft and the stent and a second biasing member (54) is operably connected to the shaft and the stent. The first and second biasing members have a first configuration cooperatively applying a longitudinal tensioning force to the stent and a second configuration cooperatively releasing the longitudinal tensioning force on the stent.