Segmented Catheter Shaft Resolving Strength-Flexibility Trade-off
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Solution Overview
Problem
Catheter shafts face challenges in achieving a balance between pushability, torqueability, flexibility, and kink resistance, as improvements in one characteristic often compromise others, making it difficult to navigate tortuous vasculature effectively during medical procedures.
Innovation Solution
A flexible catheter shaft design featuring a braided polyimide tube with a spring coil and an outer spring coil, along with a modified distal portion and specific coatings, enhances maneuverability, kink resistance, and durability by providing sufficient column strength and torque transmission while maintaining flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If thermoplastic polymer materials with secondary material reinforcement are used to provide pushability and torqueability, then column strength and torque transmission improve, but flexibility and kink resistance deteriorate
Solution Approach 1:
The catheter shaft is divided into multiple functional segments: an inner core structure (braided tube with substrate layer) providing column strength, an intermediate spring coil layer providing flexibility and kink resistance, and an outer coating layer providing torqueability. Each segment performs a specific function, allowing the overall structure to achieve pushability, torqueability, flexibility, and kink resistance simultaneously.
Solution Approach 2:
The catheter shaft employs a composite structure combining a braided polyimide tube, a substrate layer (such as PTFE/polyimide composite), and a spring coil. This multi-material composite approach allows the shaft to achieve both structural strength for pushability and flexibility for navigating tortuous vasculature, resolving the contradiction between strength and adaptability.
2Strength
If thermoplastic polymer materials with secondary material reinforcement are used to provide pushability and torqueability, then torque transmission improves, but flexibility and kink resistance deteriorate
Solution Approach 1:
The shaft is segmented into an inner braided tube structure for torque transmission and an outer spring coil structure for flexibility. The braided tube provides the torsional rigidity needed for torqueability, while the spring coil layer provides flexibility, allowing both functions to coexist without compromise.
3Strength
If catheter shafts are made with reinforced materials to improve pushability, then column strength improves, but kink resistance deteriorates
Solution Approach 1:
The spring coil acts as an intermediary element between the rigid braided tube and the outer coating. It mediates between the column strength provided by the braided tube and the need for kink resistance, allowing the shaft to maintain its shape and resist kinking while still providing sufficient flexibility to conform to vasculature.
4Ease of manufacture
If a single uniform structure is used throughout the catheter shaft, then manufacturing simplicity is maintained, but performance in different regions deteriorates
Solution Approach 1:
The catheter shaft employs local quality by modifying the distal portion differently from the proximal portion. The distal portion has a reduced number of braided layers and may have different coating characteristics to enhance flexibility where it is most needed for navigating tortuous vasculature, while the proximal portion maintains the full reinforcement structure for pushability and torqueability.
Data Source
AI summary
The present disclosure provides a strong, flexible catheter shaft for use in a catheter system. The flexible catheter shaft includes a braided polyimide tube including one or more outer layers of material of varying flexibility. The flexible catheter shaft provides a shaft having sufficient stiffness and kink resistance to allow an operator to advance an electrode basket connected to the flexible catheter shaft through a guide catheter to a target ablation site without causing vessel trauma. The distal tip of the flexible catheter shaft is designed to have sufficient flexibility to reduce any risk of kicking out a guide catheter when tracking the electrode basket around turns into side branches or bifurcations in the vasculature of a patient and includes a distal spring coil.