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Catheter having selectively varied laminationRelated Patent Categories: Plastic And Nonmetallic Article Shaping Or Treating: Processes, Direct Application Of Fluid Pressure Differential To Permanently Shape, Distort, Or Sustain Work, Producing Multilayer Work Or Article, Producing Hollow Work Or A Tubular ArticleCatheter having selectively varied lamination description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070170623, Catheter having selectively varied lamination. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD OF THE INVENTION [0001] The present invention relates to catheters comprising sections of selectively varied lamination. More specifically, the invention relates to catheters having increased flexibility towards the distal end due to at least one section of selectively varied lamination between the inner liner and outer shell, and methods for making the same. BACKGROUND OF THE INVENTION [0002] A number of intravascular procedures are currently utilized to treat a stenosis within a body vessel of a human being. A common intravascular procedure is referred to as percutaneous transluminal coronary angioplasty (PTCA or hereinafter "angioplasty"). During a typical angioplasty procedure, a guidewire is initially positioned within the body vessel and a guiding catheter is positioned over the guidewire. Next, a balloon catheter having an inflatable balloon is advanced through the guiding catheter and vessel until the balloon is adjacent to the stenosis. Subsequently, inflation of the balloon compresses the stenosis and dilates the body vessel. [0003] During many diagnostic or interventional catheterization procedures, it is necessary to route the catheter from an entry point, such as either the femoral, brachial or radial artery, to a target location within the vasculature. When properly placing a catheter into position, the catheter should be able to be turned, pulled, and pushed so that the distal end of the catheter can navigate the twists and turns of the blood vessels on its path to the final location. This requires that the catheter be rigid enough to transfer the torque being applied by the operator of the catheter, but also flexible enough so that the catheter will not damage any of the blood vessels of the patient. The catheter can be too stiff, which can prevent the catheter from passing through tortuous blood vessels. Alternatively, the catheter can be too soft, which can result in the occurrence of kinks along the length of the catheter. In either of these situations, the usefulness of the catheter in the patient is limited. [0004] In order for intravascular catheters to be neither too stiff nor too soft, it is common to make such catheters with a relatively stiff shaft and a relatively soft distal region. Typically, this variable stiffness is achieved by varying the properties of the materials used to fabricate the catheters. For example, catheters intended for use as angiography catheters or as guiding catheters often comprise a tubular liner surrounded by an outer tubular shell, with a reinforcing layer interposed there between. Either the outer shell or the liner, or both tubular elements may include relatively softer polymeric materials in a distal region of the catheter. Optionally, the reinforcing layer, which is usually a tubular braid, may also have a more flexible, modified form in the distal region. [0005] A problem that has arisen in variable stiffness catheters relates to the challenge of reliable, low-cost manufacturing, especially since many of these devices are distracted after use in only one patient. One fabrication technique taught in the prior art is to make a laminated catheter assembly with uniform polymer materials. Selected regions of the catheter are then modified by radiation treatment to selectively increase stiffness. However, this technique has not become popular due to limitations in the choice of catheter materials and in the control of the final catheter properties. It is therefore more common for intravascular catheters to have a composite construction employing different polymeric materials. [0006] One known technique for manufacturing variable stiffness catheters requires sliding a series of tubular segments having different stiffness over an inner assembly comprising a liner surrounded by a reinforcing layer. The tubular segments are shrink-fitted and melt-bonded to the inner assembly using a removable length of heat-shrink tubing. Such a process is tedious and inefficient since catheters can only be fabricated one-at-a-time. In a known reel-to-reel process, outer jacket material is varied by switching between extrusion sources as a length of inner assembly passes through a wire-coating type extruder head. Alternatively, discrete sections of one material are extruded or over-molded onto a length of inner assembly. Then, a different material is extruded onto the length of inner assembly, filling in the spaces between the discrete sections. After forming the continuous, variable-stiffness outer shell, the long assembly is cut into catheter-length sections. Such reel-to-reel processes are more cost-efficient than assembling catheters one-at-a-time. However, the use of different materials to achieve variable catheter stiffness requires multiple assembly steps and/or complex tooling, and the junctions between the different material sections require careful control of design and manufacturing to avoid potentially weak joints that could fail during use. [0007] Accordingly, there is a need for a medical catheter that is simple to manufacture and has varied properties along its length, such as varying catheter stiffness, curve retention, and overall back-up support. The present invention addresses these needs, as well as other problems associated with existing medical catheters. The present invention also offers further advantages over the prior art and solves other problems associated therewith. SUMMARY OF THE INVENTION [0008] The present invention is directed to medical catheters adapted for use within a body vessel and having variable physical properties along the length of the catheter. The medical catheter comprises a tubular catheter shaft having a distal end that fits within the body vessel. The tubular catheter shaft comprises an inner liner and an outer shell. The medical catheter comprises at least one region of selectively varied lamination between the inner liner and the outer shell. [0009] In some embodiments, at least one region of selectively varied lamination comprises a pattern of laminated sections and non-laminated sections. As examples, the non-laminated sections may be diamond-shaped or oval-shaped, the size of the non-laminated sections may increase towards the distal end, the laminated sections between non-laminated sections may decrease towards the distal end, and/or the non-laminated sections may form circumferentially arranged pairs that can be staggered at 90.degree.. The non-laminated sections increase flexibility of the catheter by intentionally permitting localized movement between the inner liner and the outer shell. [0010] In some embodiments, the distal end of the catheter comprises at least one region of selectively varied lamination, or the proximal end of the catheter comprises at least one region of selectively varied lamination, or the region of selectively varied lamination is present throughout the length of the catheter. [0011] The present invention is also directed to methods for making a medical catheter comprising at least one region of selectively varied lamination. In some embodiments, where the inner liner and outer shell can form a thermal bond, a thermal bond inhibiting agent, such as an ink or wax, is applied in a pattern to selectively inhibit thermal bonding, thus creating at least one non-laminated section. Alternately, a thermoplastic tie layer may be used to thermally bond an inner liner and an outer shell having otherwise incompatible surfaces. A pattern of gaps can be introduced into such a tie layer to produce laminated sections and non-laminated sections. In other embodiments, the inner liner and outer shell are laminated with adhesive instead of a thermal bond. The adhesive may be selectively applied to create a pattern of laminated sections and non-laminated sections. In embodiments where the inner liner requires etching or other preparation to foster adhesive bonding, the etching of the inner liner may be selectively applied or prevented, as by masking in at least one region of the inner liner. BRIEF DESCRIPTION OF THE DRAWINGS [0012] The novel features of this invention, as well as the invention itself, both as to its structure and its operation, will be best understood from the accompanying drawings, taken in conjunction with the accompanying description, in which similar reference characters refer to similar parts, and in which: [0013] FIG. 1 is a perspective view, in partial cutaway, of a medical catheter having features of the present invention; [0014] FIG. 2 is an enlarged cutaway view of a portion of the medical catheter of FIG. 1; [0015] FIG. 3 is a perspective illustration of the inventive medical catheter positioned within a patient; [0016] FIG. 4 is an enlarged side plan assembly view illustrating a grooved portion of a catheter shaft in accordance with the present invention; and [0017] FIGS. 5-7 illustrate catheters in accordance with the present invention, wherein sections of the outer shell have been removed to show a variety of regions of selectively varied lamination. DETAILED DESCRIPTION OF THE INVENTION [0018] The present invention is directed to a catheter that has at least one region of selectively varied lamination. Any multi-layered medical catheter can be modified to have regions of selectively varied lamination. The catheters described herein are merely exemplary and the invention should not be construed to be limited to only the catheters described herein. [0019] Referring to FIGS. 1, 2 and 4, a first embodiment of medical catheter 10 having features of the present invention includes tubular catheter shaft 12, hub 14, and tubular flexible tip 16. Catheter shaft 12 can optionally include groove 18, which is cut out of catheter shaft 12 near distal end 20 of catheter shaft 12. Continue reading about Catheter having selectively varied lamination... 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