Steerable Sheath Pull-Wire Layout for Predictable Torque Response
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Solution Overview
Problem
Steerable introducers experience issues with pull wires breaking or whipping due to stored energy when torque is applied with the sheath in a deflected position, leading to unpredictable movements and potential failure.
Innovation Solution
The steerable sheath design incorporates pull wires and electrode wires arranged in non-overlapping helical patterns along the non-deflectable portion and straight paths in the deflectable portion, combined with reflowed polymeric layers, to manage torque application and reduce energy storage, preventing wire breakage and whipping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If pull wires are arranged in straight lines from proximal to distal end, then the sheath can be steered effectively, but the pull wires store energy when torque is applied in deflected positions causing wire breakage or whipping
Solution Approach 1:
The pull wires are configured to follow a helical path around the inner liner in the non-deflectable portion of the sheath instead of a straight line. This curved/helical arrangement allows the wires to accommodate torque application more effectively, reducing stored energy and preventing breakage or whipping while maintaining steering capability through the deflectable portion.
2Measurement precision
If the sheath is made deflectable at the distal end, then steering precision is improved, but torque application causes unpredictable movements and potential failure
Solution Approach 1:
The sheath is divided into distinct segments: a non-deflectable portion with a helical pull wire arrangement and a deflectable portion with a straight pull wire arrangement. This segmentation allows each portion to perform its specific function - the helical portion manages torque and the straight portion enables precise deflection - thereby improving both steering precision and control predictability.
Data Source
AI summary
A steerable sheath includes an inner liner extending from a proximal to a distal end of the steerable sheath. The inner liner includes a non-deflectable portion and a deflectable portion. The steerable sheath includes a first pull wire positioned along a first helical path around the circumference of the inner liner from a proximal to a distal end of the non-deflectable portion and along a first straight path from a proximal to a distal end of the deflectable portion. The steerable sheath includes a second pull wire positioned along a second helical path around the circumference of the inner liner from the proximal to the distal end of the non-deflectable portion and along a second straight path from the proximal to the distal end of the deflectable portion. The steerable sheath may also include electrode wires present in a helical or spiral pattern around the circumference of the steerable sheath.