Surgery – Means for introducing or removing material from body for... – Treating material introduced into or removed from body...
Reexamination Certificate
1998-05-04
2001-12-04
Sykes, Angela D. (Department: 3734)
Surgery
Means for introducing or removing material from body for...
Treating material introduced into or removed from body...
C604S532000, C604S264000, C600S433000
Reexamination Certificate
active
06325790
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a catheter, and in particular to a composition used in a torsion control catheter.
Torsion control catheters, such as angiographic or guiding catheters, are designed for intravascular use in the treatment of disease and typically have a soft, flexible tip member connected to a tubular body. The body is formed of a relatively stiff material such as a nylon or a stiff polyurethane to provide torqueability, burst pressure strength and longitudinal rigidity sufficient to advance the catheter in arteries and other tortious pathways in the body.
Torsion control catheters must be able to transmit a twisting or torsional force along their length to permit twisting forces applied at a proximal end portion of the body to be transmitted along the longitudinal axis of the catheter to the distal end portion of the body at which the tip is disposed. In this way, the catheter can be guided through arteries and the like. However, in doing so, the twisting and forward movement of the catheter poses a risk of injury or trauma to the surrounding tissue. Accordingly, it is generally desirable for such catheters to have a soft tip on one end of the body which is more flexible than the body. The soft tip prevents injury to the vessels and arteries as the catheter is advanced in the body and facilitates the guidability of the catheter.
Various polymer compositions for catheter bodies and for catheter soft tips have been proposed. Many of the catheter soft tips formed from these compositions suffer from limitations inherent in the thermal and/or physical properties of the tip materials. For example, some materials, such as polyamide block copolymers, exhibit too much memory. As a result, tips made from these materials tend to want to retain their shape, and may cause trauma to vessels when advanced in the body and may hinder guidability. Other materials do not bond well to commonly preferred body materials, or may become too soft at body temperature.
The present invention is directed to a catheter employing a soft tip having advantageous thermal and physical properties that overcome the problems associated with prior art catheters.
DESCRIPTION OF THE INVENTION
The soft tip torsion control catheter constructed in accordance with the present invention employs a copolymer composition that has heretofore not been employed in a soft tip torsion control catheter. The physical properties of the present soft tip copolymer composition can be easily modified by altering the relative amounts of the various monomers in the copolymer, making it easily adaptable to the requirements of different catheters. In particular, the composition is advantageously easily modified to exhibit desirable stiffness and memory, and it bonds well to a wide range of preferred body materials. For example, due to its relatively low and sharp melting point, it is more easily bonded to stiffer materials, such as nylon 11 and nylon 12, than commonly used polyamide block copolymers. It also bonds well to maleic anhydride modified polyethylene, unlike polyamide block copolymers, yielding advantages in design choice and ease of manufacture. Moreover, various grades of the soft tip copolymer can be blended with each other, or with various grades of a nylon (e.g., nylon 11 or nylon 12) to provide a wide range of stiffnesses. Polyamide block copolymer compositions do not blend well with each other. As a result, soft tip catheters employing the present copolymer composition exhibit advantages as compared to the prior art.
In one embodiment of the present invention, the present soft tip copolymer composition is used in a torsion control soft tip catheter comprising a tubular body, and a soft, flexible tip member connected to the tubular body. The soft tip member is formed from a material comprising a copolymer of polyamide monomers with monomers of polyamide having lower alkyl side chain groups attached to a polyamide backbone.
More specifically, the copolymer used in the distal catheter soft tip of the invention comprises a first monomer that is a polyamide monomer of the formula:
and a second monomer that is a polyamide side chain monomer of the formula:
where x is from 0 to 11, y is equal to or greater than 1 and z is from 0 to 11, with the proviso that the sum of x, y and z is an integer from 9 to 11. The polyamide monomer is present in an amount of from about 50 to about 90% by weight based on the weight of the first and second monomers, and the side chain monomer is present in an amount of from about 10 to about 50% by weight based on the weight of the monomers. The subscript m is an integer from 9 to 11. The number of side chains in the second monomer is random, but is at least one. Preferably, y is equal to 1. The value of n may be an integer from 2 to 9, and is preferably 6.
In addition to the copolymer, the distal soft tip member may also include radiopaque material, colorants, and other additives known in the art. Suitable colorants, such as titanium oxides, and suitable radiopaque materials, such as bismuth subcarbonate, bismuth oxychloride, bismuth trioxide, tungsten metal and barium sulfate, are commercially available and would be known to those of ordinary skill in the art in view of the instant disclosure.
The catherer body may be formed from a polyamide or other material having suitable properties. Suitable body materials include polyurethane, polyethylene, nylon 11 or nylon 12, or blends of these as is known in the art. In the case of guiding catherers, an innermost tube may be used for improved lubricity. One composition of this lubricious innermost tube is TEFLON® brand polytetrafluoroethylene. Another composition is this lubricious innermost tube is comprised of a vinylic polymer and one of an unsaturated carboxylic acid and an anhydride of the carboxylic acid, in particular, a copolymer of polyethylene and maleic anahydride. The body may include radiopaque material, colorant, and other commonly used additives. Although the bodies of torsion control catherers typically include inner and outer tubes separated by a reinforcing braid to impart good torqueability while retaining adequate flexibility, the present invention contemplates torsion control catherers that may be braided or unbraided.
In a preferred form the present torsion control soft tip catheter comprises a tubular body having two end portions, the body being formed from a nylon having desired stiffness for torqueability, burst strength and longitudinal rigidity. A soft, flexible tip portion is connected to one of the body end portions and is formed of a material that is preferably more flexible than material of the body. The tip portion is formed from a copolymer including a first monomer of polyamide and a second monomer having a polyamide backbone with a seven carbon (heptyl) side chain group as described above.
The present catheter soft tip composition overcomes the problems of the prior art compositions. It has suitably low memory as to enhance guidability while avoiding the danger of puncturing or traumatizing surrounding tissues during use. The physical properties of the present catheter soft tip copolymer can be easily modified to accommodate various needs based on the effect of the side chain groups on the crystallinity of the copolymer. The side chains hinder the crystallinity of the copolymer. By increasing or decreasing the frequency of the side chains, such as by changing the relative percentage of the side chain monomer in the copolymer, the crystallinity and hence, flexibility or softness of the tip can advantageously be modified.
Moreover, by blending the noted copolymer with like copolymers having different percentages of the polyamide side chain monomer, and/or by blending it with various polyamides, one can obtain a material with a wide range of flexibility from that approximating pure nylon 11 or 12, to that of a 50:50 copolymer of polyamide and side chain monomer. Accordingly, the copolymer of the invention may be modified for use in the catheter body when the percentage of polyamide in th
Bianco Patricia
Cordis Corporation
Hoffman Watts
Hoffman & Heinke
Sykes Angela D.
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