Introducer sheath (10,30,40) having a flexible kink-resistant distal tip portion (26,32,42). A multilayer sheath structure is used, with an inner tube (12) such as PTFE having a coil (14) of wire wound therearound. A first length of outer tubing (20) such as of nylon is inserted over most of the coil-wound inner tube (12) in a manner exposing a distal length of coil-wound inner tube. A second length of outer tubing (22) with a softer durometer than first outer tubing length (20), is inserted over the exposed coil-wound inner tube and extends for a slight distance beyond the end of the coil. During heat application, the outer tubing lengths (20,22) are melted to bond to each other and to flow between the spacings of the coil turns to bond to the roughened outer surface of the inner tube (12). The distal tip region corresponding to the second tubing length is flexible and is kink-resistant due to the coil (14).

FIELD OF THE INVENTION

The present invention relates to the field of medical devices and more particularly to introducer sheaths.

BACKGROUND OF THE INVENTION

Introducer sheaths are well-known for percutaneous vascular access and typically comprise polytetrafluoroethylene or fluorinated ethylene propylene. These sheaths are of a thin-walled construction, but tend to kink, which is unacceptable since upon kinking the sheath is unusable and cannot be straightened while positioned in the body of a patient and must therefore be removed leaving an enlarged, bleeding opening which typically cannot be reused for the necessary percutaneous entry. Increasing the thickness of the sheath wall only minimally improves the level of kink resistance while enlarging the entry hole which generally is undesirable.

One introducer sheath with improved kink resistance is disclosed in U.S. Pat. No. 5,380,304 to Parker. The introducer sheath comprises a coil having a plurality of turns positioned and compression-fitted around an inner tube. An outer tube is connected to the inner tube through the uniform spacing of the coil turns. As a result, the compression-fitted coil reinforces the wall to provide an extremely kink-resistant and thin-walled introducer sheath. Preferably, the coil comprises flat wire for minimizing the wall thickness of the sheath.

The distal ends of the inner and outer tubes extend beyond the distal end of the coil, and the distal end of the outer tube is tapered and extends beyond the distal end of the inner tube to advantageously prevent the inner tube from presenting a rough edge or surface, which may cause injury to the vessel wall. The outer tube is said to comprise a heat-formable polyamide material such as nylon for connecting with the rough outer surface of the inner tube, between the coil turns. A distal tip member of nylon is then bonded onto the distal tip of the outer tube, and is of the same durometer, or is harder to further facilitate entry into the percutaneous access site.

It is desired to provide a kink-resistant introducer sheath that has a more flexible distal tip, enabling introducer sheaths to be utilized in applications involving more tortuous paths or more sensitive treatment sites.

SUMMARY OF THE INVENTION

The foregoing problems are solved and a technical advance is achieved in an illustrative flexible, kink-resistant, introducer sheath having a flexible distal tip portion. The sheath of the present invention includes an inner tube such as of polytetrafluoroethylene, and a flat wire coil wound therearound. A first length of outer tubing of a conventional relatively hard material such as of nylon, extends along most of the length of the coil-wound inner tube. A second, short length of outer tubing is selected to have a softer durometer than the first length of outer tubing, and is placed over the exposed coil-wound length of the inner tube and abutted against the end of the first length of outer tubing. Both first and second lengths of outer tubing are melted to flow between the spacings of the coil wire to bond to the roughened outer surface of the inner tube and to thermally bond to each other at the abutment location. After appropriate tapering of the distal end of the second outer tubing length, a sheath is fabricated having a flexible distal tip portion.

Thus, the present invention provides an introducer sheath for use in applications such as renal and other arterial applications involving tortuous vascular paths and that has an atraumatic flexible kink-resistant distal tip portion.

DETAILED DESCRIPTION

FIGS. 1 and 2show an introducer sheath assembly100of the prior art, as in U.S. Pat. No. 5,380,304. A dilator102extends through a passageway of sheath104such that a tapered distal tip106of dilator102extends beyond the tapered distal end108of sheath104. Sheath104also includes a connector valve110affixed at its proximal end112, that includes a silicone disk (not shown) for preventing the backflow of fluids therethrough. Connector valve110also includes a side arm114to which polyvinyl tube116and Luer lock connector118are connected for introducing and aspirating fluids therethrough. Tapered distal end106of dilator102facilitates accessing and dilating a vascular access site over a well-known and commercially available wire guide (not shown). A Luer lock connector hub120is attached at the proximal end of the dilator for connection to syringes and other medical apparatus.

Depicted inFIG. 2is a partially sectioned view of Prior Art introducer sheath104, with dilator102removed from longitudinal sheath passageway122. Sheath104comprises an outer tube124, an inner tube126of polytetrafluoroethylene (PTFE), and a flat wire coil128compression fitted around inner tube126within outer tube124. Outer tube124is joined to the roughened outer surface130of inner tube126between the spacings of the coil, in accordance with the disclosure of U.S. Pat. No. 5,380,304, wherein during fabrication a sleeve of heat shrinkable tubing is placed around the outer tube, a mandrel inserted through and beyond inner tube126, and heat applied until the outer tube melts to flow between the spacings of the wire coil, being urged thereinto by shrinking of the heat shrink sleeve, which is thereafter removed. Pursuant to the patent, a distal tip portion132is thermally bonded to a tapered distal end134of outer tube124, and is of the same durometer as outer tube124, or harder, and has a tapered end that forms tapered distal end108of sheath104. Inner surface136of PTFE inner tube126is lubricious and slippery to facilitate insertion and withdrawal of dilator102and of catheters and the like therethrough. Proximal end138of sheath104is flared to facilitate retention thereon of valve110.

In the present invention illustrated inFIGS. 3 to 6, sheath10includes an inner tube12corresponding to inner tube126ofFIG. 2, with a roughened outer surface and preferably of PTFE, and flat wire coil14wound spirally therearound. A mandrel16is inserted through passageway18of inner tube12, and a first length of outer tubing20(or proximal outer tubing) is placed over much of the length of the coil-wound inner tube12, with a selected length of the coil-wound inner tube remaining exposed. First outer tubing length20may be of for example nylon having a durometer of between about 50 D and 60 D (Shore D hardness) and may preferably be about 56 to 58 D. However, in certain applications it may be desired for the first outer tubing to have a hardness of up to 80 D.) A second, short length of outer tubing22(or distal outer tubing) of nylon having a softer durometer than first tubing length20, such as between about 35 D and 45 D and preferably about 39 D, is then placed over the exposed length of coil-wound inner tube12and abutted against the end of first outer tubing length20. The exposed length of coil may be about 5 mm to 1 cm or more beyond the distal end of the first outer tube for prevention of kinking at least at the junction of the first and second outer tubing lengths, and the coil may extend if desired for almost the entire length of the second outer tubing, such as for an infusion/drainage catheter with multiple side ports along an extended length.

Regarding the durometer of the second length of outer tubing22, in applications such as superselective tracking catheters where the leading end must negotiate small, tortuous vessels, the durometer may be selected to be as low as about 10 D for being optimally atraumatic. In other applications such as introducer catheters for placement of stents and various interventional devices where torque transfer and pushability are desired, the durometer of the second tubing length may be selected to be, for example, only about 5 D lower than that of the first length of outer tubing20, such as about 45 D where the first length20is about 50 D.

A length of heat shrinkable sleeve24is placed over the entire arrangement, and ends thereof are preheated to shrink at ends of the assembly to hold the first and second lengths against each other. Preferably the first and second lengths of outer tubing20,22are distinctly different in color or at least shade, such that abutment can be assured by visual inspection through transparent heat shrinkable sleeve24.

Upon heating to melt the outer tubing lengths20,22to flow between the turns of the coils to bond to inner tube12while being compressed by the shrinking of heat shrinkable sleeve24, a distal tip portion26results that is flexible due to the softer durometer of second outer tubing length22, and that is kink-resistant due to coil14. After fabrication the heat shrunk sleeve24is removed. A taper is then formed adjacent the distal tip of the sheath for a length of about 6 mm, such as by conventional grinding. Optionally, a hydrophilic coating is applied to the outer surface of the sheath.

As seen inFIG. 5, one embodiment of sheath30the present invention can have a distal tip region32that is linear in form and that is elongate such as about 7 cm, especially suitable for vascular applications involving tortuous paths, the elongate flexible kink-resistant distal tip portion being atraumatic. Also seen is a radiopaque marker band34positioned about one-quarter inch from tip36. InFIG. 6is seen another embodiment sheath40having distal tip region42that is formed into an arcuate section by placing the fabricated sheath under elevated temperatures while being constrained in a template of appropriate curvature; for example, a flexible kink-resistant distal tip portion of about 2.5 cm with such curvature is especially suitable for use in entering the renal ostium and eases stress to the renal artery. Preferably, such curvature extends about an angle of about 90°. Where it is desired for the sheath to have a distinct curvature, it would be desirable for the durometer of the second outer tubing length to have a durometer closer to that of the first outer tubing length, such as its durometer being only about 5 D or 10 D lower than that of the first outer tubing length.

The second outer tubing length can have a length of from about 1 cm to about 7 cm and preferably is hydrophilic coated. Preferably a radiopaque marker band, such as of platinum alloy or tungsten or gold, is positioned about the distal end of the coil prior to placement of the outer tubing lengths thereover and thermal bonding, whereafter the marker band becomes embedded within the outer tubing. Additionally, for certain applications it is preferred that the second outer tubing length have a content of radiopaque filler, such as between about 20% and 85%, and preferably about 80%, by weight of tungsten or barium sulphate particles or the like, while the first outer tubing length substantially does not have a radiopaque filler content.

Additionally, it may be desired to provide at least one intermediate outer tubing length between the first and second outer tubing lengths, with a respective durometer between that of the first and second tubing lengths.

The inner tube preferably comprises one continuous tube, but it can be an arrangement formed from two or more tubes fixed in an end-to-end relationship. The use of two or more inner tubes enables the durometer to be reduced in a distal direction in a manner similar to that of the outer tube arrangement which can have two or more outer tubes. The junctions in the inner arrangement would clearly need to be offset from those in the outer arrangement, if there were at least two parts in both the inner and outer tube arrangements.