Catheter Delivery Device Helical Wire Reinforcement
Solution Overview
Problem
Catheter delivery devices face challenges in deploying lengthy covered stents due to high end-to-end stresses, which can lead to buckling and loss of length integrity, particularly in narrow tortuous lumens, as existing systems struggle to effectively transfer tensile and compressive stresses along the catheter shaft.
Innovation Solution
The catheter delivery device features a novel architecture with a casing tube and a pull wire system that includes a distal sheath with a diving tube and a stent support tube, along with a helical wire wrapping to enhance column strength and resist compressive stresses, allowing for the deployment of lengthy covered stents through narrow lumens by transferring stresses efficiently and minimizing the risk of buckling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the catheter delivery device uses a narrow passing diameter to minimize catheter size, then the device complexity is reduced and ease of navigation is improved, but the catheter shaft cannot sustain the high end-to-end compressive stresses during deployment of lengthy covered stents, leading to buckling and loss of length integrity
Solution Approach 1:
The catheter shaft employs a composite construction combining a polymer tube with an embedded helical wire reinforcement. The polymer matrix provides flexibility and navigability through tortuous lumens, while the helical wire component provides high compressive strength to prevent buckling during stent deployment. This composite structure resolves the contradiction by integrating materials with complementary properties.
Solution Approach 2:
The helical wire wrapping creates a curved, spiral reinforcement pattern around the catheter shaft. This helical geometry efficiently distributes compressive loads along the length of the catheter while maintaining flexibility. The curved structure allows the catheter to bend and navigate tortuous pathways without compromising its ability to resist buckling under compression.
2Length of moving object
If the catheter delivery device is designed for lengthy covered stents (up to 120 mm or beyond), then the stent length and stenting force are improved, but the end-to-end stresses during deployment increase significantly, requiring a more robust delivery system that conflicts with the goal of maintaining a narrow passing diameter
Solution Approach 1:
The composite catheter shaft with helical wire reinforcement is specifically engineered to handle the increased end-to-end stresses associated with deploying lengthy covered stents. The helical wire provides the necessary tensile and compressive strength to maintain catheter integrity over the extended length required for stents up to 120 mm or beyond, while the polymer matrix maintains flexibility for navigation.
Solution Approach 2:
The helical wire reinforcement is pre-installed and integrated into the catheter shaft construction before deployment. This preliminary reinforcement ensures that the catheter is pre-configured to withstand the high stresses that will occur during stent deployment, eliminating the need for additional reinforcement mechanisms during the procedure and maintaining a relatively narrow profile.
3Device complexity
If the catheter delivery device uses a pull wire architecture to deploy self-expanding stents, then the deployment mechanism is simplified, but the system must incorporate a transfer zone to invert stress from compression to tension, creating a vulnerable point for buckling
Solution Approach 1:
The helical wire reinforcement continuously traverses the entire length of the catheter shaft, including the transfer zone where stress inversion occurs. This continuous reinforcement eliminates weak points by providing uniform structural support throughout, preventing buckling at the critical transfer zone while maintaining the simplicity of the pull wire deployment mechanism.
Solution Approach 2:
The helical geometry of the wire reinforcement creates a distributed reinforcement pattern that smoothly transitions through the transfer zone. The curved, spiral configuration allows stress to be gradually redistributed along the catheter length rather than concentrated at a single point, reducing the risk of buckling at the stress inversion point.
Data Source
AI summary
A catheter delivery device for a self-expanding stent is described. The delivery device includes a distal catheter component and a distal sheath that releases the stent by moving proximally relative to the distal catheter component and the stent. A proximal catheter shaft including a tube and a pull wire within a lumen of the tube may be provided, the pull wire being attached to the distal sheath such that pulling the pull wire proximally relative to the tube pulls the distal sheath proximally to release the stent progressively. A casing tube may be provided to surround the catheter shaft, the casing tube having a distal end that receives telescopically a proximal end of the distal sheath.