External Pull Wire Fixation for Stent Delivery Catheters
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Solution Overview
Problem
Existing stent delivery systems face challenges in preventing proximal movement of self-expanding stents during deployment, despite the use of continuous metal strands to resist such movement, as the stent can still be placed undesirably proximal to the intended location.
Innovation Solution
The delivery system incorporates fixation elements, such as heat shrink material loops or slidable rings, to locate the pull wire outside the catheter shaft, reducing complexity and enhancing the transfer of tensile stresses while minimizing bowing of the catheter shaft, thereby maintaining precise placement of the stent.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the pull wire is disposed within a lumen of the catheter shaft, then the delivery system structure is simplified, but the transfer of tensile stresses is reduced and bowing of the catheter shaft increases
Solution Approach 1:
The pull wire is extracted from the internal lumen of the catheter shaft and repositioned to run externally along the outer surface of the catheter shaft. This extraction resolves the contradiction by enabling direct tensile stress transfer from the hand unit to the sheath while reducing catheter shaft bowing, though it increases structural complexity through the addition of fixation elements
2Strength
If the pull wire is disposed outside the catheter shaft, then the transfer of tensile stresses is enhanced and bowing is reduced, but the device complexity increases
Solution Approach 1:
Fixation elements serve as intermediaries between the external pull wire and the catheter shaft, securing the pull wire to the outer surface at multiple points. These fixation elements enable effective tensile stress transfer and bowing reduction while containing the added complexity to specific localized components rather than the entire system
3Reliability
If a continuous metal strand is used to resist proximal movement of the stent, then proximal movement is partially controlled, but residual proximal movement still occurs
Solution Approach 1:
The pusher element is positioned to abut the stent and provide preliminary counter-action against proximal movement forces generated during sheath retraction. This preliminary anti-action, combined with the external pull wire configuration, eliminates residual proximal movement and ensures precise stent placement at the intended location
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 configuration minimizes the risk of stent proximal movement, ensuring accurate deployment at the intended site by reducing the gap between the catheter shaft and pull wire, thus maintaining the stent's position within the bodily lumen.
Implementation Method 1
heat shrink material loops
Data Source
AI summary
A method of making a delivery system for a prosthesis includes providing a catheter shaft, sliding a plurality of rings over the catheter shaft, each of the rings having an inner diameter larger than an outer diameter of the catheter shaft, fixing a pull wire to each of the plurality of rings at a common circumferential location of the catheter shaft, and coupling a sheath to the pull wire, the sheath positioned over the prosthesis at a distal end of the catheter shaft. Fixing the pull wire to each of the plurality of rings can include wrapping a heat shrink film around each of the plurality of rings and the pull wire, and heating the heat shrink material.