Tapered Outer Catheter Reduces Stress Risers in Stent Delivery
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Solution Overview
Problem
Conventional delivery systems for radially expandable stents face issues with stress risers and kinking when navigating tortuous pathways, particularly at high angle bends, leading to decreased trackability and potential catheter failure.
Innovation Solution
A delivery system featuring a coaxial tubular assembly with a gradual inward taper and abrupt outward taper in the distal portion of the outer tubular member, reducing stress concentrations and improving flexibility, combined with a holder band to maintain the stent position, enhances trackability and stability during deployment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional delivery catheter structure is used, then the catheter can be inserted into the vessel, but stress risers occur at the junction of inner and outer catheters causing the catheter shaft to bend or fail during passage through tortuous pathways
Solution Approach 1:
The outer catheter is truncated to terminate proximal to the distal end of the inner catheter, removing the problematic junction area where stress risers occur. This extraction of the problematic section eliminates the source of stress concentration while maintaining the functional integrity of the delivery system.
Solution Approach 2:
The outer catheter incorporates a tapered distal portion with varying wall thickness, creating local quality variations that reduce stress concentrations. The gradual taper transitions from a first wall thickness to a second, thinner wall thickness, allowing stress distribution optimization at the critical distal region without compromising overall catheter strength.
2Ease of operation
If the delivery system traverses a high angle bend or tortuous pathway, then the catheter must navigate the complex anatomy, but kinking and decreased trackability occur due to high stress in the system
Solution Approach 1:
The outer catheter's distal portion features a tapered structure with varying wall thickness, creating local quality variations that optimize flexibility and stress distribution. This allows the catheter to navigate tortuous pathways and high angle bends without kinking, improving trackability while maintaining reliability.
Solution Approach 2:
The delivery system is divided into distinct segments: an inner catheter with full length, and a truncated outer catheter with a tapered distal portion. This segmentation allows each component to be optimized independently - the inner catheter provides structural support while the truncated outer catheter with its tapered geometry provides flexibility for navigating complex anatomy.
Data Source
AI summary
A system for delivery of a medical device to a target site within the body of a patient includes an introducer sheath, and a delivery assembly receivable within a passageway of the sheath. The delivery assembly comprises an inner tubular and an outer tubular member. At least a distal portion of the inner tubular member has a diameter such that the medical device is receivable thereover. The outer tubular member is generally coaxial with the inner tubular member, and has a length such that the outer tubular member distal end terminates proximal to the inner tubular member distal portion. The outer tubular member has a first outer diameter at the proximal end and extends for a length of the outer tubular member to a first diameter boundary point. The outer tubular member has a gradual inward taper in the distal direction from the boundary point to a second outer diameter, and has an abrupt outward taper in the distal direction from the second diameter to the first diameter.