The advantages of laser-cut tube (LCT) catheters
The medical device community has a long history of using braided and coil-based catheter constructs. But these traditional constructs present multiple performance-based issues. “With the advent of the laser-cut tube capability we have at Resonetics, it’s opened up a lot of options for catheter manufacturing,” said Dave Rezac, VP of design and development services at the company, in a recent DeviceTalks Tuesdays webinar.
Kevin Hartke, Resonetics’ chief technical officer, joined Rezac in the Resonetics-sponsored webinar to discuss how their company studied the comparative performance of LCT versus traditional catheter constructs.
Here are four takeaways on how LCT compares to the traditional catheter construct:
1. Different catheter construction
The catheter construction process consists of layering individual components — the mandrel, liner, reinforcement layer, and jacket — and turning them into a composite-reinforced catheter by fusing them through heat and pressure. Rezac termed it “like a slow-motion molding process.”
The traditional construct contains these layers as well as a tie layer and classic braid or coil.
2. A different design process
Customers often ask Resonetics, “What information do we need to develop an LCT?” Rezac said, “It’s surprisingly little. We can work with functional requirements and target specifications.”
Resonetics asks questions like, “What does it have to do? How much load does it have to carry? Where is it going?”
“We translate those functional requirements into the pattern,” Hartke said. “That’s one of our offerings as a business; we have a nice library of patterns and a full understanding of how those patterns affect the functional output of the device or the part.”
3. Different components
Key components for LCT are the liner, reinforcement layer and jacket:
•Liner: The liner is placed over a core material to define the lubricious inner lumen. Liner options include PTFE, HDPE, FEP and PVDF and ePTFE. In deciding on the liner, essential considerations are performance requirements and cost.
•Reinforcement layer: Traditional braids and coils can be cumbersome. Manufacturers can experience processing challenges when using both on the same catheter. LCT can be game-changing, especially with high-end novel applications, because LCT decouples traditional torque, column strength and flexibility relationships. In addition, it is highly tunable and continuously variable. “The reinforcement layer was really the star of our study,” Rezac said.
•Jacket: The jacket defines the catheter’s interaction with the outside world. It helps define and amplify or offset the mechanical properties of the underlying layers.
4. Different test methods and results
Resonetics tested bending stiffness, kink resistance/ovality, tensile strength, and torque transfer in comparing catheter constructs. Here’s what Resonetics found:
•Bending stiffness: There was parity between LCT and traditional construct. It’s possible to design LCT for a variety of bending stiffnesses across typical values seen with braid and coil.
•Kink resistance/ovality: Kink resistance and lumen integrity are paramount in many interventional applications. LCT reinforced shafts maintain excellent kink resistance and lumen integrity through bends, demonstrating extreme resistance to ovalization. “This is where LCT started to differentiate itself and pull away,” Rezac said.
•Tensile strength: LCT reinforced catheter shafts exhibit acceptable tensile and compressive strength. Rezac reported “comparable or similar flexibility, improved kink resistance, no ovality, and comparable tensile strength.” He added: “You’re not sacrificing a lot of integrity and tensile and compression to get these advantages.”
•Torque transfer: Catheter shafts exhibit superior torque transmission with LCT as compared to conventional braid construction. “This is where LCT really blows the conventional methods out of the water,” Rezac said. “This is a huge differentiator for the applications space.”
LCT has multiple advantages, according to Resonetics. Monolithic design can achieve the mechanical performance of braid, coil, or a combination of the two. It is highly tunable and stable. It eliminates the need for braid and coil wire termination and transitions. It provides superior hoop strength and lumen integrity, ensuring smooth passage and actuation of devices through the inner lumen while operating in tortuous anatomy. And it is compatible with conventional liners, jackets and lay-up manufacturing processes.
“Generally speaking, you can achieve cost parity in a lot of these constructions,” Rezac said. “The LCT component might be a larger portion of your cost; however, you’re saving headaches downstream . . . by and large you’re moving some costs around.” Hartke noted that Resonetics “is able to manufacture [LCT] parts that are price competitive to a standard catheter construct.”
Article source: Medical Tubing Extrusion