Varying Diameter Wire Collection for Stent Deployment
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Solution Overview
Problem
Current stent delivery systems face challenges in maintaining accurate stent positioning and controlling deployment due to resistance issues between the inner and outer catheters, and between the stent and vascular walls, requiring excessive force and often necessitating assistance, especially when deploying longer stents.
Innovation Solution
A wire collection device with a thumbwheel and collection spindle that provides a mechanical advantage by varying the collection diameter, allowing the retraction wire to collect around a spiral groove, thereby maintaining a consistent rotating force and reducing the binding force between the stent and outer sheath, enabling easier and more controlled stent deployment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a pin and pull system is used for stent deployment, then the stent can be deployed through the outer sheath, but the user experiences difficulty maintaining inner catheter position due to resistance between components
Solution Approach 1:
A release mechanism is introduced as an intermediary component between the outer sheath and stent. This mechanism includes a retention member that can be selectively moved from a retained position to a released position, mediating the interaction between the sheath and stent to control deployment forces and reduce resistance during the procedure.
Solution Approach 2:
The system changes the mechanical parameters of the deployment process by using a release mechanism that selectively alters the friction and binding forces between the outer sheath and stent. By transitioning from a retained to released state, the system modifies force requirements dynamically during deployment.
2Ease of operation
If the outer sheath is retracted to deploy the stent, then the stent is released, but the varying binding force makes deployment difficult to control
Solution Approach 1:
The release mechanism serves as a mediator that standardizes the force transmission during sheath retraction. By controlling when and how the retention member transitions from retained to released position, the system provides more predictable and controllable deployment forces throughout the procedure.
Solution Approach 2:
The system dynamically adjusts the mechanical interaction between sheath and stent through the movable retention member. The transition from static retention to dynamic release allows the operator to control the deployment process more precisely, adapting force application to the specific stage of deployment.
3Productivity
If the user moves the handle faster to deploy longer stents, then deployment speed increases, but control difficulty increases
Solution Approach 1:
The release mechanism provides a controlled interface that decouples handle movement speed from actual deployment speed. By managing the retention and release states, the system allows operators to maintain better control even during faster deployment of longer stents.
4Ease of operation
If the user holds the distal ends of the outer sheath and inner catheter, then direct control is achieved, but the user cannot monitor positioning in the hemostasis valve
Solution Approach 1:
The release mechanism acts as an intermediary control point that allows indirect monitoring and control of catheter positioning. By observing and controlling the retention member's state, the operator can infer positioning accuracy without directly holding the distal ends, enabling better spatial awareness during the procedure.
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 solution provides a consistent 'touch and feel' for the user, reducing the variation in applied force and allowing for accurate stent placement with improved control and reduced need for assistance, even during deployment of longer stents, by increasing the deployment distance with less hand movement.
Implementation Method 1
A wire collection device with a thumbwheel and collection spindle that provides a mechanical advantage by varying the collection diameter
Implementation Method 2
The retraction wire collects around the collection spindle along a spiral groove formed between the varying collection diameter and the substantially constant outer diameter
Data Source
AI summary
A stent delivery system includes a wire collection device which is constructed with a thumbwheel coupled to a collection spindle that is rotatable to collect a retraction wire about a varying collection diameter of the collection spindle. A proximal end of an outer stent-constraining sheath is coupled to the collection spindle by the retraction wire and a distal end of the outer sheath retractably surrounds a distally-disposed self-expanding stent. The collection spindle includes a substantially constant outer diameter greater than the varying collection diameter, and the varying collection diameter increases from a first end of the spindle towards a second end of the spindle along a spiral groove formed between the varying collection diameter and the substantially constant outer diameter in a manner that provides substantially constant rotating force on the thumbwheel, thereby accommodating changing resistance as the outer sheath is retracted and releases binding force of the stent.