Bi-Directional Steerable Catheter With Pull-Ring Control
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Solution Overview
Problem
There is an ongoing need for alternative steerable medical devices that can navigate tortuous anatomy and efficiently deliver medical implants or conduct treatment procedures, as existing devices may have limitations in maneuverability and flexibility.
Innovation Solution
A bi-directional steerable catheter design featuring an elongate sheath with a reinforcing braid, steering wires, and a distal pull ring, allowing for precise control and bending in two directions through a handle mechanism with a pulley wheel and tensioning system, enhancing navigation and maneuverability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a catheter uses a simple straight structure, then it is easy to manufacture, but it cannot navigate tortuous anatomy effectively
Solution Approach 1:
The catheter shaft is divided into multiple segments including a distal portion, intermediate portion, and proximal portion, each with different flexibility characteristics. The shaft also includes multiple lumens for different functions (guidewire lumen, catheter lumen, sheath lumen). This segmentation allows the catheter to navigate tortuous anatomy while maintaining manufacturability through modular construction.
Solution Approach 2:
The catheter incorporates a shape memory alloy wire (Nitinol) that can change its shape in response to temperature changes. The catheter can be delivered in a straight configuration and then transformed into a curved configuration at the target site by applying heat, enabling it to adapt to tortuous anatomy dynamically.
2Strength
If a catheter uses multiple layers and reinforcing braids, then it has improved strength and stability, but it increases manufacturing complexity
Solution Approach 1:
The catheter shaft is constructed as a composite structure with multiple layers including an inner tubular sleeve, reinforcing braids (first and second reinforcing braids), and an outer tubular sleeve. The shape memory alloy wire is embedded within these layers. This composite construction provides enhanced strength and stability while using well-established manufacturing techniques for each layer.
Solution Approach 2:
The catheter employs a nested structure where the shape memory alloy wire is embedded within the inner tubular sleeve, which is surrounded by reinforcing braids, which are in turn surrounded by an outer tubular sleeve. This nested arrangement maximizes strength while maintaining a compact profile and facilitating systematic manufacturing.
3Ease of operation
If a catheter has a distal pull ring and steering wires, then it provides bidirectional steering control, but it increases device complexity
Solution Approach 1:
The distal pull ring acts as an intermediary element that the operator grasps to apply tension to the shape memory alloy wire, causing the catheter to bend in a controlled manner. The steering wires extend from the handle to the distal portion, mediating the transmission of forces from the operator's hands to the catheter shaft, enabling bidirectional steering without complex mechanical mechanisms.
Solution Approach 2:
The shape memory alloy wire provides self-service by automatically changing the catheter's shape in response to applied tension and temperature changes. Once tension is applied through the pull ring, the wire's shape memory properties cause the catheter to bend toward the desired configuration without requiring additional active control mechanisms.
Data Source
AI summary
An elongate sheath may include an inner sleeve, a reinforcing braid over the inner sleeve, a pull ring between the inner sleeve and the braid, steering wires extending proximally from the pull ring, and an outer sleeve encompassing the braid. The steering wires extend between the inner sleeve and the braid to an exit location distal of the proximal ends of the inner and outer sleeves. A second reinforcing braid may be spaced apart from the braid proximal of the exit location. A method of making an elongate sheath may include positioning an inner sleeve on a mandrel, positioning a pull ring over the inner sleeve, wherein steering wires extend proximally from the pull ring, positioning a reinforcing braid over the inner sleeve, pull ring, and steering wires, positioning an outer sleeve over the braid, surrounding the outer sleeve with shrink wrap, and applying heat to reflow the outer sleeve.