Variable Diameter Trigger Wire for Self-Expanding Medical Device Delivery
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing trigger wires for self-expanding medical device delivery systems require varying levels of bending and tensile strength, but constant cross-section wires fail to efficiently manage these demands, leading to suboptimal device retention and deployment, particularly in navigating smaller body vessels with lower-profile delivery systems.
Innovation Solution
The design incorporates trigger wires with varying diameters, where the proximal portion has a greater diameter than the distal and center portions, allowing for adequate bending strength to retain the device and sufficient tensile strength for withdrawal, enabling a lower-profile delivery system by forming bends that compress the self-expanding medical device and allowing for a smaller delivery sheath and inner member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If constant cross-section trigger wires are used, then the wire can provide adequate tensile strength for withdrawal, but the wire cannot provide sufficient bending strength for device retention without increasing overall wire diameter
Solution Approach 1:
The trigger wire is designed with variable cross-section where different portions have different diameters optimized for their specific functions. The proximal portion has a larger diameter (e.g., 0.008-0.012 inches) to provide sufficient bending strength for device retention, while the distal portion has a smaller diameter (e.g., 0.002-0.004 inches) to minimize delivery system profile. This local differentiation allows each section to have the precise mechanical properties needed without requiring the entire wire to be oversized.
Solution Approach 2:
The trigger wire is divided into distinct functional segments: a proximal portion for device retention requiring high bending strength, a center portion for withdrawal requiring tensile strength, and a distal portion for handle connection requiring moderate bending strength. Each segment is optimized independently with appropriate diameter, allowing the wire to perform multiple functions simultaneously without compromise.
2Strength
If larger diameter trigger wires are used to provide adequate bending strength, then device retention is improved, but the delivery system profile increases preventing access to smaller body vessels
Solution Approach 1:
The variable cross-section trigger wire concentrates the larger diameter only where bending strength is critically needed (proximal portion forming the retention bend), while the majority of the wire length (distal portion) maintains a small diameter. This allows the delivery system to navigate small body vessels while still providing adequate retention force at the device location.
3Strength
If the trigger wire proximal portion has sufficient bending strength for device retention, then the wire can be withdrawn through the delivery system, but the wire cannot form an adequate connection to the handle at the distal end
Solution Approach 1:
The trigger wire is segmented into functional zones with the distal portion having increased diameter relative to the center portion to provide adequate bending strength for handle connection and manipulation. This segmentation ensures that each end of the wire has the mechanical properties required for its specific operational role.
Solution Approach 2:
The wire diameter is locally increased at the distal portion where handle connection and operator manipulation occur, while maintaining smaller diameter in the center portion for minimal delivery profile. This localized adaptation allows adequate handle connection strength without compromising the overall delivery system size.
Data Source
AI summary
A self - expanding medical device delivery system includes a plurality of trigger wires (30). The trigger wires retain a self - expanding medical device (24) by forming a bend (36) about structural members located on the proximal portion of the medical device. The proximal portions (32) of the trigger wires have a greater diameter than the distal portions (34) of the trigger wires to provide increased bending strength. An operator releases the self - expanding medical device by withdrawing the trigger wires in the distal direction. In some embodiments, a small portion at the proximal end of the trigger wire has a smaller diameter than the rest of the proximal portion. In other embodiments, the proximal and distal portions of the trigger wire each have a greater diameter than the center of the trigger wire.