Etching a substrate: processes – Forming or treating cylindrical or tubular article having...
Reexamination Certificate
2000-04-20
2003-03-25
Olsen, Allan (Department: 1746)
Etching a substrate: processes
Forming or treating cylindrical or tubular article having...
C216S041000, C216S052000, C216S092000, C216S100000
Reexamination Certificate
active
06537459
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to an etched tubular device, particularly cylindrical, biocompatible medical devices for insertion into a body during medical procedures and to a method for manufacturing these devices. More particularly, the invention relates to flexible tubular devices for use as stents, catheters (including, for example, guide catheters and balloon catheters, guidewires, catheter sheaths, microcircuitry containing catheters, catheter introducers and drug infusion catheters/guidewires) and methods for making these devices.
Catheters and Guidewires
Catheters are relatively thin and flexible tubes used in the medical field for numerous applications. Catheters are made by any number of different methods and designs. However, in most catheter designs it is desirable to obtain a maximum torsional rigidity while retaining a satisfactory longitudinal flexibility and stiffness without kinking. These features allow the catheter to be manipulated so that the catheter can be guided through small body vessels and cavities. These features will also prevent any kiking from occurring, and provide the catheter with sufficient stiffness to prevent the catheter from wrinkling or folding back on itself during this process. The specific nature of these characteristics vary depending on the specific application for which the catheter is being used. Another consideration is that a relatively small outside diameter must be maintained while providing a lumen or an inside diameter as large as possible.
Guidewires require the same general type of physical characteristics. However, with guidewires it is important to minimize the outside diameter of the guidewire so that they will readily fit inside of the lumen of the catheter.
Catheters and guidewires are used both as diagnostic tools and therapeutic tools in the treatment of diseases. One such diagnostic procedure is cardiac catheterization which is a widely performed procedure, being used for assessment of coronary artery disease. Other uses are neurologic uses, radiologic uses, electrophysiologic uses, peripheral vascular uses, etc. Example of therapeutic uses are balloon catheterization in dilation procedures to treat coronary disease and retroperfusion delivery of drugs at targeted sites within the human body. Dilation procedures rely upon the use of a catheter for injection of contrast and delivery of guidewires and dilation catheters to the coronary artery or other arteries. An example of the use of guidewires is for Percutaneous Transluminal Coronary Angioplasty (PTCA) balloons and for guiding diagnostic catheters through the arteries and to body organs. Retroperfusion drug delivery requires the use of the catheter to guide a tube carrying the drug to be delivered, and in some cases to have the catheter determine part of the rate of perfusion by the size, number and distribution of openings in the catheter through which the drug will pass.
The catheters and guidewires used in these and other procedures must have excellent torque characteristics, and must have the requisite flexibility. In addition, it is important that catheters and guidewires provide sufficient longitudinal support for “pushing” of items through the arteries and other vessels such as when feeding the balloon portion of an angioplasty catheter through the arteries. Unless there is sufficient stiffness, the catheter or guidewire will wrinkle or fold back on itself
Typically, in the case of a catheter, the larger the ratio of inside to outside diameter, the better, even while striving for minimum outside diameters for the catheters. Smaller catheter and guidewire outside diameter sizes result in less chance of arterial damage.
Catheters and guidewires must have sufficient torque to reduce buckling when being manipulated. Additionally, flexibility is important so that the catheter or guidewire can be manipulated into the varying arterial branches encountered by the catheter. The guidewire must resist being inadvertently kinked, as this can result in loss of torque control.
Prior art catheters are typically made of flexible materials which are reinforced such that the resulting composite catheter approximates the desired characteristics. In alternative approaches, guidewires are used in conjunction with catheters to assist in manipulating and moving the catheters through the arterial system in the body.
Stents are small, expandable tubes, usually used for insertion into a blocked vessel (vein or artery or duct) or other bodily part. Their physical characteristics must often be the same as those for catheters, except for the fact that they also must be expandable. This expansiveness is effected, not by elastic expansion under pressure, as is the case with balloons or parachutes in surgical procedures, but by more spring-like, metal memory characteristics in the material. Stents are often formed of a metal tube which is compressed (without exceeding the elastic flexibility or stress of the metal), inserted, and then released to allow the stent to expand to its original size and shape.
U.S. Pat. No. 4,020,829 discloses a spring guidewire for use in catheterization of blood vessels. The guidewire is axially slidable within a thin-walled, flexible plastic catheter. The distal portion of the guidewire is of a relatively short length and is connected to a relatively long, manipulative section capable of transmitting rotational torque along its length. In this invention the catheter tube might be advanced over the guidewire after the guidewire has been properly positioned or the catheter might be advanced together with the guidewire, the guidewire providing a reinforcement for the thin wall of the catheter.
U.S. Pat. No. 4,764,324 discloses a method for making a catheter. A reinforcing member is heated and applied to a thermoplastic catheter body so as to become embedded in the wall of the catheter. The wall of the catheter is then smoothed and sized so as to produce a composite, reinforced catheter.
Current catheters often suffer from either problems of torque, size, flexibility, kinking, and poor support during PTCA in the case of guide catheters. Moreover, catheters cannot be readily made with variable stiffness along the length of the catheter.
Catheter Sheaths and Introducers
Catheter sheaths and introducers are used to provide a conduit for introducing catheters, fluids or other medical devices into blood vessels. A catheter introducer typically comprises a tubular catheter sheath, a hub attached to the proximal end of the sheath having hemostasis valve means to control bleeding and to prevent air embolisms, and a removable hollow dilator that is inserted through the hub, valve means and the lumen of the catheter sheath. Many catheter introducers also contain a feed tube that is connected to the hub to facilitate the introduction of fluids into the blood vessel.
Positioning an introducer into a blood vessel begins by inserting a hollow needle through the skin and into the lumen of the desired blood vessel. A guidewire is then passed through the needle and into the blood vessel. The needle is then removed leaving the guidewire in the vessel. Next, the sheath and dilator are advanced together over the guidewire until the distal ends of the dilator and sheath are positioned within the lumen of the vessel. The guidewire and dilator are then removed, leaving the distal end of the sheath within the vessel. Catheters or other medical devices can then be passed through the introducer and sheath into the desired vessel.
Conventional sheaths are made of plastic and are subject to kinking if bent without internal support. This kinking can occur during the insertion of the device or if the patient moves while the sheath is in the vessel. Unfortunately, this kinking can create sharp edges or irregularities in the sheath that can damage blood vessel linings. This kinking can also make the introduction of devices or fluids more difficult and can cause patient bleeding problems around the sheath tubing. Therefore, there arises a need
Dufresne Michael J.
Lundblad LeRoy J.
BMC Industries, Inc.
Olsen Allan
Oppenheimer Wolff & Donnelly LLP
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