Curved Cross-Section Pull Wire for Vascular Stent Deployment
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Solution Overview
Problem
Pin and pull systems for deploying vascular intervention devices, such as self-expanding stents, face challenges in maintaining accurate stent positioning and control during deployment due to difficulty in simultaneously pulling the outer sheath and resisting the inner catheter, leading to potential inaccuracies, damage, or early partial deployment.
Innovation Solution
A vascular intervention device delivery system featuring a catheter with a retractable sheath and a pull wire with a curved cross-section that provides columnar support and controlled tension, reducing friction and allowing precise deployment by winding the pull wire onto a spool to maintain tension without premature sliding of the sheath.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a pin and pull system is used to deploy a self-expanding stent, then the stent can be delivered and deployed, but the user has difficulty maintaining the inner catheter at a fixed position while simultaneously moving the outer sheath, leading to inaccurate stent positioning
Solution Approach 1:
A pull wire is introduced as an intermediary element that connects the outer sheath to the inner catheter. The pull wire transmits the pulling force from the outer sheath to the inner catheter, allowing the user to control both components simultaneously through a single pulling action rather than requiring coordinated two-handed operation. This mediator resolves the operational difficulty and improves positioning accuracy.
Solution Approach 2:
The delivery system is segmented into distinct functional components: the outer sheath, the inner catheter, and the pull wire. This segmentation allows each component to have a specific function - the outer sheath for delivery and protection, the inner catheter for support and positioning, and the pull wire for controlled deployment. The segmented structure enables independent optimization of each component's performance.
2Ease of operation
If high force is applied during stent deployment, then the stent can be deployed, but the force decreases as more of the stent is deployed, causing the stent to be deployed too fast for the user to control
Solution Approach 1:
The pull wire system provides dynamic force transmission that adapts to the deployment process. As the stent deploys and the outer sheath retracts, the pull wire maintains continuous tension, allowing the user to modulate the deployment speed by controlling the pulling force in real-time. The system transitions from high initial force to controlled lower force as deployment progresses, preventing runaway deployment.
Solution Approach 2:
The pull wire provides tactile feedback to the user during deployment, allowing the user to sense the resistance and deployment progress through the wire. This feedback mechanism enables the user to adjust the pulling force to maintain controlled deployment speed, preventing the stent from deploying too quickly as the deployment force decreases.
3Adaptability or versatility
If the user pauses during deployment and releases built-up tension in the outer sheath, then the deployment can be paused, but deployment errors occur when the user resumes tension to move the outer sheath
Solution Approach 1:
The pull wire maintains continuous tension and connection between the outer sheath and inner catheter throughout the deployment process, including during pauses. This continuous action prevents loss of control or positioning when the deployment is paused and resumed, ensuring reliability and accuracy is maintained throughout the entire procedure.
4Reliability
If friction on the retractable sheath is high during maneuvering to the delivery site, then the sheath can be positioned, but early partial deployment of the stent can occur
Solution Approach 1:
The pull wire provides a counterbalancing force that offsets the frictional resistance on the outer sheath during maneuvering to the delivery site. By applying controlled tension through the pull wire, the system prevents the sheath from moving prematurely due to friction, thereby preventing early partial deployment of the stent while maintaining reliability.
Data Source
AI summary
A vascular intervention device delivery system includes a catheter with a proximal end attached to a handle, and a distal carrier segment for mounting a vascular intervention device thereon. A retractable sheath is movable from a first position covering the distal carrier segment to a second position retracted proximally uncovering the distal carrier segment. A pull is attached to the retractable sheath and extends proximally from the retractable sheath toward the handle. A majority of the length of the pull has a cross sectional shape with a concave side that faces the longitudinal axis and is opposite to a convex side that faces away from the longitudinal axis. The cross sectional shape has a width that is greater than a thickness.