Braided Shafts for Steering & Deflection

Steering vs. Deflection

Steering and deflection – what is the difference? When a braided shaft is “steered” the tip has a defined shape and movement occurs along the full length of the shaft. When a braided shaft is “deflected” only the tip of the shaft moves and the full length of the shaft remains stationary.

Braided shaft designs with steering and deflecting capability are ideal for EP and AF catheter applications including introducer and support sheaths, diagnostic, mapping and ablation devices.

Manufacturing Approaches:

Steerable shafts are typically shape set. Sets are achieved through a simple mold and heat manufacturing process. Deflecting shafts are more complex and require the integration of multiple pull wires into the braided shaft to achieve control of movement. Movement can be uni-directional or bi-directional and symmetrical or asymmetrical

Wall Tolerances:

A constant challenge for the design of braided shafts is how to lower the shaft profile while maintaining performance. By addressing the wall thickness of the shaft an optimum balance can be achieved. Creganna Medical has developed manufacturing techniques that enable the tightest of tolerances to be held between walls, lowering the overall shaft profile. For example, on a 2F or 3F shaft, tolerances of +/- 0.001” can be achieved for standard designs. As the French size increases, tolerance will become broader. Another alternative to braided shafts are coiled shafts. Wall thickness can be decreased considerably using coil shaft designs.

Design Considerations:

When considering a steering or deflectable shaft for your catheter design, here are some issues that should be addressed early in the design phase.
  • What is the nature of the vasculature or anatomical structure the catheter will navigate? For complex access techniques to the left atrium or ventricle, coronary sinus or for transeptal access you may wish to consider a deflectable shaft. Enhanced push, flexibility and kink resistance may also be required for challenging access sites.
  • What type of deflecting movement is required? Should the catheter simply curl or does it need to curl and reach?Through what bend radius should the deflection be delivered?
  • Does the shaft need to play a support or guiding function for other devices?
  • Ergonomic handle design is critical for the deployment and control of a deflectable shaft. Are self braking/locking mechanisms required? Is the handle optimized for visual and tactile feedback for the physician? Can the device be deployed via single handed use?

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