Lubricous and readily bondable catheter shaft

Details Lubricous and readily bondable catheter shaft Lubricous and readily bondable catheter shaft

1999-04-09

2001-04-17

Kennedy, Sharon (Department: 3763)

Surgery

Means for introducing or removing material from body for...

Treating material introduced into or removed from body...

C604S103000

Reexamination Certificate

active

06217547

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to catheters for performing intravascular procedures such as percutaneous transluminal coronary angioplasty (PTCA) and more specifically to elongated shafts for such catheters.
PTCA is now one of the most widely used treatment modalities for heart disease. The procedure basically comprises advancing a dilatation catheter, having an inflatable balloon on its distal extremity, into the patient's coronary anatomy over a guidewire until the balloon of the dilatation catheter is properly positioned across the lesion to be dilated. Once properly positioned, the dilatation balloon is inflated with liquid to a predetermined size at relatively high pressures, e.g. up to 20 atmospheres or more, to expand the arterial passageway. Generally, the inflated diameter of the balloon is approximately the same diameter as the native diameter of the body lumen being dilated so as to complete the dilatation but not overexpand the artery wall. After the balloon is finally deflated, blood flow resumes through the dilated artery and the dilatation catheter can be removed therefrom.
In most PTCA procedures, a guiding catheter having a preshaped distal tip is first percutaneously introduced into the cardiovascular system of a patient by means of a conventional Seldinger technique and advanced therein until the preshaped distal tip of the guiding catheter is disposed within the aorta adjacent to the ostium of the desired coronary artery. The guiding catheter is twisted or torqued from its proximal end, which extends out of the patient, to guide the distal tip of the guiding catheter into the desired coronary ostium. Once the guiding catheter is in proper position within the patient's vasculature, the dilatation catheter with a guidewire slidably disposed within an inner lumen of the dilatation catheter is positioned within the inner lumen of the guiding catheter. The guidewire is first advanced out the distal tip of the guiding catheter seated in the coronary ostium into the patient's coronary artery and directed to the region of the patient's coronary anatomy where the procedure is to occur. A torque may be applied to the proximal end of the guidewire, which extends out of the proximal end of the guiding catheter, to guide the curved or otherwise shaped distal end of the guidewire into a desired branch of the coronary artery. The advancement of the guidewire within the selected artery continues until it crosses the lesion to be dilated. The dilatation catheter is then advanced over the previously advanced guidewire, until the balloon on the distal extremity of the dilatation catheter is properly positioned across the lesion which is to be dilated.
Current intravascular catheter designs are limited by the need to incorporate conflicting characteristics. For example, most dilatation catheters are designed to be introduced into a body lumen over an in-place guidewire which is slidably received within an inner lumen within the catheter. As such, it is desirable to minimize the friction between the guidewire and the surface of the inner lumen of the catheter by constructing the catheter from a lubricous material such as a high density polyethylene. However, lubricous polymeric materials frequently lack other desirable properties, including, for example, the ability to readily bond to incompatible polymeric materials such as polyethylene terephthalate and nylon. Due to the high inflation pressures (up to 300 psi or more) associated with coronary balloon angioplasty, it is imperative to provide a strong bond between one or more ends of the dilatation balloon and the catheter shaft. Polyolefin balloons can be effectively fusion bonded to a polyethylene shaft but balloons made of nylon and other polyamide materials, and balloons made of polyesters such as polyethylene terephthalate do not easily bond to polyolefinic materials. Nylon and polyethylene terephthalate balloons usually require surface treatment and the use of a suitable adhesive to bond to polyolefin materials such as polyethylene. The additional manufacturing steps of surface treatments and incorporating and curing an adhesives, greatly complicate the manufacturing process and can introduce significant quality control problems. A catheter shaft should also have adequate strength for pushability and resistance to buckling or kinking. As another example, it may be desirable to provide a catheter shaft with elastomeric properties to improve flexibility. However, most lubricous materials are not elastomeric.
U.S. Pat. No. 5,304,134 to Kraus et al., which is hereby incorporated in its entirety by reference, attempts to provide a solution to the poor bonding of lubricous by providing the catheter shaft with an inner tubular member having a lubricous proximal portion and a non-lubricous, bondable distal portion. However, this approach does not represent a complete solution, because the lubricous proximal portion must still be bonded to the non-lubricous distal portion. The Kraus et al. system also requires that some portion of the guidewire lumen be formed from a non-lubricous material which restricts guidewire movement within the lumen.
A different approach involves forming the dilatation balloon as an integral portion of the catheter shaft itself, but this requires the balloon and the shaft to be formed from the same material, which is not always desirable because the property requirements for the balloon and the shaft can be quite different, particularly for dilatation catheters for PTCA .
Accordingly, there remains a need to provide a catheter shaft having a lubricous inner surface defining a guidewire lumen while allowing an easy, secure bond with a dilatation balloon or other catheter components formed of non-lubricous polymeric materials. The present invention satisfies these and other needs.
SUMMARY OF THE INVENTION
The present invention is directed to an intraluminal catheter, such as a balloon dilatation catheter for performing angioplasty procedures, which has a shaft or shaft segment which is both lubricous and is capable of readily bonding to other catheter components such as a balloon formed of essentially non-lubricous polymers.
In one embodiment of the invention, the catheter shaft or catheter shaft segment is formed of a polymeric blend comprising at least about 30% by weight, preferably at least about 50% by weight, of a lubricous polymeric component not more than about 60%, preferably not more than about 40%, of a bonding polymeric component and up to about 30%, preferably not more than about 10%, of a polymeric component for compatiblizing the lubricous and bonding components. Optionally, up to 25% by weight, usually not more than about 10% by weight of the blend could be a catalytic material to facilitate cross linking the shaft material to enhance compatiblizing. The lubricous component and the bonding component are not compatible, or miscible in the molten state. As used herein the term “compatible” and words of similar import mean that two polymer materials readily form an intimate mixture when they are melt processed together. However, the relative amounts of the different polymeric components of the polymeric blend will depends upon, and will therefore vary with, the nature of the polymeric materials.
Suitable lubricious polymeric components include polyolefins, such as polyethylene and polypropylene. One preferred lubricious polymeric material is high density polyethylene (HDPE), and most preferably high molecular weight HDPE having a molecular weight of about 50,000 to about 200,000. High density polyethylene has a density of at least about 0.94. The high molecular weight material has a high modulus of about 220,000 psi which provides improved collapse resistance for a given catheter shaft wall thickness.
In one embodiment, the bonding component comprises a polyamide polymeric material. Suitable polyamide materials include nylon, such as nylon
6
, nylon
6
,
12
, nylon
6
,
6
, nylon
11
, nylon
12
. The preferred nylons are typically semicrystalline, alth

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