Surgery – Means for introducing or removing material from body for... – Treating material introduced into or removed from body...
Reexamination Certificate
1999-12-02
2004-09-28
Short, Patricia A. (Department: 1712)
Surgery
Means for introducing or removing material from body for...
Treating material introduced into or removed from body...
C604S264000, C525S183000, C525S184000, C525S425000, C525S432000
Reexamination Certificate
active
06796958
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to a novel polymer blend that can be extruded, molded, or otherwise formed into articles of manufacture having certain desired characteristics. As examples, the polymer blend of the invention can be processed to form medical catheters and more particularly concerns a balloon material for medical balloon dilatation catheters made from blends of a first crystalline polymer component, and a second softening polymer component. The balloon material can also include a third compatibilizing polymer component. While the invention herein relates generally to polymer blends, it will be discussed in terms of preferred end uses in medical devices such as catheters and dilatation balloons. The subsequent discussion is not meant to be limiting and is by way of examples and preferred uses.
2. Description of Related Art
Catheters are well known for their usefulness in medical applications and in particular angioplasty procedures, for opening blood vessels or other passageways in the body that may be blocked by obstructions or stenosis. Dilation catheters are generally formed from thin, flexible tubing having an inflatable balloon at or near a distal tip of the tubing that can be inflated with fluid pressure communicated to the balloon through a lumen of the tubing. In a typical angioplasty procedure, the balloon dilatation catheter is passed through the vasculature to the location of a stenosis in an artery, and the balloon is inflated to a predetermined size and shape to open the blocked artery.
It is desirable for balloons of balloon dilatation catheters to be capable of inflating to a diameter of typically five to six times their uninflated diameter in order to be able to open an obstructed vessel. Other desirable properties of balloons for such balloon dilatation catheters include strength, softness, flexibility and a thin, low profile which are important for achieving the performance characteristics of folding in an uninflated state, tracking, crossing and recrossing the area of the obstruction or stenosis in a vessel in an uninflated state. In addition, properties of burst strength, compliance, fatigue have been increasingly important in the continuing effort to create thinner, lower profile balloons for balloon dilatation catheters with an ability to track, cross and recross increasingly narrow passages in obstructed vessels. For purposes of this description, the ability to cross is defined as the ability of a balloon of a balloon dilatation catheter to pass through a stenosis; the ability to recross is defined as the ability of the balloon of a balloon dilatation catheter to pass through a stenosis more than once, or to pass through more than one stenosis; and the ability to track is defined as the ability of balloon of a balloon dilatation catheter to pass over a guidewire through the tortuous curves of the vasculature, in being guided to and from the location of a stenosis.
Polymeric materials that have been used for making medical devices, catheters, dilatation catheters, and balloons for balloon dilatation catheters include polyethylene, polyolefins, polyvinyl chloride, polyester, polyimide, polyethylene terephthalate (PET), polyamides, nylon, polyurethane, and the like. Balloons made of soft polyolefin or ethylene copolymers materials are typically foldable, and track and cross well, so that they can often be used more than once, and can be used to cross multiple lesions. However, such balloons also commonly have high balloon compliance and low burst strengths, with ratings of rated burst pressure of about 8-9 atm, and a mean burst pressure of about 10-15 atm. Balloons made from polyethylene terephthalate (PET) are commonly stronger, with a higher rated burst pressure of about 14-18 atm, and a mean burst pressure of about 18-25 atm. However, dilatation catheter balloons made of PET are generally stiff, not readily foldable and refoldable, and are susceptible to acquiring defects from mechanical handling. Dilatation catheter balloons made of PET are also susceptible to pin-hole failures that can cause jet-streaming of pressurized fluid within an artery, and can lead to a dissection of the artery. As a result, to reduce the likelihood of pin-hole failures, clinical applications of balloons made of this type of material have generally been limited to thicker balloons that are commonly limited to a single use, and for crossing a single lesion.
Examples of prior art compositions that may be suitable in forming medical devices such as catheters, dilatation catheters, and balloon materials for use in angioplasty procedures include U.S. Pat. No. 4,753,980 (Deyrup); U.S. Pat. No. 4,172,859 (Epstein); U.S. Pat. No. 5,091,478 (Saltman); U.S. Pat. No. 5,306,246 (Sahatjian et al.); U.S. Pat. No. 4,254,774 (Boretos); U.S. Pat. No. 4,964,409 (Tremulis); and U.S. Pat. No. 5,017,325 (Jackowski et al.), all of which are incorporated herein by reference. These references are presented by way of example only and are not intended to be exhaustive of the prior art.
It would be desirable to provide a polymeric blend for balloons for balloon dilatation catheters with a combination of the best features of the softer balloon materials and the stronger balloon materials, including good flexibility, folding, track, cross and recross, with a thin, low profile, high resistance to fatigue, low compliance, and high burst strength, with a lower susceptibility to defects through mechanical handling, and a lower susceptibility to pinhole defects, compared with balloons made from PET. The present invention meets these needs.
SUMMARY OF THE INVENTION
Briefly, and in general terms, the present invention provides for a catheter and/or balloon material formed from a blend of polymeric components that has surprisingly high rated and mean burst pressure characteristics, low compliance and excellent fatigue resistance, along with excellent folding and performance characteristics, such as track, cross and recross, allowing for construction of dilatation catheter balloons with the ability to cross multiple lesions.
The invention accordingly provides for a catheter and/or balloon material formed from a blend composition of a first crystalline polymeric component and a second softening polymeric component. When the first and second polymeric components are essentially incompatible in that they are immiscible, and do not normally bond together well, a third compatibilizing agent that helps to strengthen the interface between the two incompatible materials and to facilitate blending of the first two polymeric components can be added to the balloon material.
The first polymeric component generally consists of about 10-95% by weight of the total blend composition, and in one preferred embodiment can be a polyester prepared from the group of dicarboxylic acids selected from aromatic dicarboxylic acids having from 8 to 14 carbon atoms and aliphatic dicarboxylic acids having from 2 to 12 carbon atoms, and at least one glycol selected from the group consisting of glycols having the formula HO(CH
2
)
n
OH, where n is an integer from 2 to 10, neopentyl glycol and cyclohexane dimethanol. In an alternative embodiment, the first polymeric component can be a branched or straight chain polyamide having a molecular weight of at least about 5000. The second polymeric component generally consists of about 5-90% by weight of the total blend composition, is selected to have a Shore hardness less than 75 D, and preferably less than 55 D, and is selected from the group consisting of ethylene copolymers, polyolefins having a density less than 0.93, polyester block copolymers and polyamide block copolymers. The third polymeric component generally consists of an amount of a compatibilizing ethylene copolymer that is less than about 2.5% by weight of the total balloon material blend, and preferably about 0.25% to about 2.5% by weight of the total balloon material blend, and has the formula E/X/Y where E is ethylene; X is an &agr;, &bgr;-ethylenically unsaturated mo
Chen Ziyun
Cheng Tai
Muni Ketan
Patel Udayan
Saltman Robert
Advanced Cardiovascular Systems Inc.
Fulwider Patton Lee & Utecht LLP
Short Patricia A.
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