Steerable Catheters

Steerable Catheters

When it comes to designing, developing, and manufacturing high quality, predictable, steerable catheters, Midwest Interventional Systems can’t be beat. By leveraging our experiencing in managing complex steerable delivery systems from concept through commercialization, we help guide our clients through the development, ultimately getting them to market faster and within budget.

We start our approach to steerable catheter design by defining design outputs, which include:

  • Bend angles
  • Bend diameters
  • Planes of deflection
  • Dimensional specifications

These outputs are driven by the anatomy and the approach. We have direct experience in designing and developing steerable systems for applications such as:

  • Steerable structural heart delivery systems - Transcatheter mitral valve and tricuspid valve delivery systems, Left atrial appendage closure delivery systems
  • Steerable ablation catheters
  • Robotically controlled steerable catheter systems
  • Steerable microcatheters

Once the desired functional requirements are determined for your catheter system, our design engineers begin designing the components of the delivery system to achieve the desired outputs.

Steerable Catheter Design Process

Mandrels

The first component to consider in steerable catheter design does not actually make it into the final product – This component is the processing mandrel. Depending on the design requirements for the inner lumen of the steerable shaft, the following must be considered:

  • Thermal properties during reflow/lamination
  • Geometry considerations - mandrel grooving, radius considerations
  • Surface treatments

Liners

The next component MIS evaluates in the design process is the liner material for the main lumen and pull wire lumens for the catheter. Liners are lubricious material that line the inner diameter of lumens to reduce frictional forces from passing other instruments, catheters, devices, and in the case of steerables, pull wires through these lumens. There are a number of options for liner material to incorporate into the delivery system, and they ultimately depend on the application. Common liner materials typically consist of:

  • Film cast or ram extruded and etched PTFE
  • FEP, etched
  • Standard thermoplastic extrusions with lubricious additives
  • Polyimide

Reinforcement

The next layer to a steerable catheter delivery system is either a lamination aid or a reinforcement layer. The reinforcement layer plays a critical role in the overall device torqueability, achievable bend angles and bend diameters, kink resistance, and pushability. Depending on the application of the device, performance requirements, and other interacting devices, MIS engineers have a plethora of options in their catheter reinforcement toolbox, including, but not limited to:

- Braid reinforcement

  • Round and flat wire
  • Single, dual, tri, & quad start wire
  • Variable pitch braiding
  • Braid pattern and number of carriers
  • Material: 304 & 316 Stainless steel, nitinol, tungsten, UHMWPE, etc.

- Coil Reinforcement

  • Round and flat wire
  • Clockwise and counterclockwise winding
  • Single or multilayered
  • Variable pitch coiling
  • Material: 304 & 316 Stainless steel, nitinol, tungsten, UHMWPE, etc.

- Braid/Coil Hybrid

- Laser cut hypotubes and polymers

Pull Ring and Pull Wire Assembly

At the distal end of the reinforcement segment of a catheter, it is common to abut a steering assembly. Most commonly this includes a pull ring and pull wire assembly; however, there are other technologies like magnets and coaxial steering mechanisms that can be employed. For the majority of steerable systems, a pull ring and attached pull wire will be employed and act as acritical component which drives the articulation of the overall catheter system. Several items that we consider during pull wire and ring development are:

  • Ring and wire material selection
  • Round or flat pull wire design
  • Pull ring design
  • Welding
  • Pull wire to ring tensile
  • Force to deflect the overall system

Jacket

The final layer in constructing a steerable delivery system is the jacket, or medical extrusion. The extrusions provide coverage over the reinforcement layer of the catheter and are also critical to the device torqueability, flexibility, compression and elongation resistance. MIS will help in developing a number of specifications surrounding these jackets, which include:

  • Material selection – Polyamides, thermoplastic elastomers (TPEs), and thermoplastic urethanes (TPUs)
  • Single and multilumen extrusion design
  • Selective durometer placement and material transition considerations
  • Catheter distal tip forming
  • Hydrophilic coating

Contact us today to discuss how we can help determine the optimal approach to design your articulating catheter, and partnering with you on the development of your delivery system.

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