Catheter

This invention relates to a catheter, for example, a catheter to be inserted into a blood vessel such as a catheter for angiography or a catheter for dilating a blood vessel.

A catheter for angiography to be inserted into a blood vessel consisting of a main body formed of a somewhat soft thermoplastic resin and a rigidity imparting member consisting of a metallic braided wire (generally a stainless-steel wire) and disposed around the main body which is for inhibiting kinking or squash of the catheter while maintaining its high flexibility and for improving the torque transmission efficiency has conventionally been designed.

A catheter equipped with an inflatable member for dilating a stenosis portion in a blood vessel to improve the blood flow on the peripheral side of the stenosis portion which is for use in curing the stenosis portion is disclosed in EPA No. 349640 for example. This catheter comprises an inner tube made of a flexible synthetic resin, an outer tube made of a flexible synthetic resin and disposed coaxially with the inner tube and a foldable and inflatable member having a proximal end portion attached to the outer tube and a distal portion attached to the inner tube, and besides, the inner or outer tube is provided with a rigidity imparting member consisting of a metallic wire (e.g., a stainless-steel wire).

The rigidity imparting member used in the above catheter can inhibit its kinking or squash and improve its torque transmission efficiency to some extent. However, the catheter as a whole had low rigidity and particularly had a low efficiency of transmitting the pushing force given at its proximal end (pushability) and only an insufficient torque transmission efficiency.

Catheters are required to be introduced into peripheral blood vessels. Catheters which can be introduced into a more peripheral blood vessel have now become more and more desirable.

However, the above catheter, whose body portion consists of a synthetic resin tube, needs to have a certain wall thickness and therefore necessarily has a large outer diameter. Accordingly, the blood vessel into which the catheter can be introduced is restricted by its outer diameter and the catheter could only be introduced into a blood vessel sufficiently larger than the outer diameter of the catheter.

The object of the present invention is to provide a novel and improved catheter of the design that a high efficiency of transmittting the pushing force given at its proximal end (pushability) and a high torque transmission efficiency and furthermore can be made to have a sufficiently thin wall thickness and a smaller diameter.

According to the present invention, there is provided a catheter comprising an inner tube which has a body portion, a distal portion and a first lumen whose tip is open; an outer tube which is disposed coaxially with said inner tube, has a body portion, a distal portion and a distal tip recessed by a predetermined distance from a distal tip of the inner tube and forming a second lumen between an inner surface of said outer tube and an outer surface of said inner tube; a deflatable or foldable and inflatable member which has a tip portion attached to the inner tube and a rear end portion atached to the outer tube and communicates with the second lumen near said rear end portion; a first opening disposed at the proximal portion of said inner tube and communicating with the first lumen; and a second opening disposed at the proximal portion of the tube and communicating with the second lumen, wherein at least one of the body portions of the inner and outer tubes includes a super-elastic metallic tube. The invention will now be described on hand of several non limitative examples illustrated on the annexed drawings. <ul id="ul0001" list-style="none" compact="compact"><li>Fig. 1 is a partial longitudinal cross section of a catheter according to a preferred embodiment of the present invention.</li><li>Fig. 2 is a partial longitudinal cross section of a catheter according to another preferred embodiment of the present invention.</li><li>Fig. 3 is a view showing the proximal end of a catheter according to one preferred embodiment of the present invention.</li></ul>

As shown in Fig. 1 and 2, the catheter 60 comprises an inner tube 61 having a body portion 64a, a proximal end portion 64b and a first lumen 66 whose tip is open; an outer tube 63 which is disposed coaxially with the inner tube 61, has a body portion 64a and a distal portion 64a, has a distal tip recessed by a predetermined distance from the distal tip of the inner tube 61 and forms a second lumen 67 between it and the outer surface of the inner tube 61; a deflatable or foldable and inflatable member 68 which has a tip portion attached to the inner tube 61 and a rear end portion attached to the outer tube 63 and communicates with the second lumen 67 near the rear end portion, a first opening 72 shown in Fig. 3 disposed at the proximal end portion of the inner tube and communicating with the first lumen 66; and a second opening 71 shown in Fig. 9 disposed at the proximal end portion of the outer tube 63 and communicating with the second lumen 67. At least one of the inner tube 61 and the outer tube 63 includes a super-elastic metallic tube.

The catheter 60 consists of the inner tube 61, the outer tube 63, the inflatable member 68 and a branched hub 70.

The body portion 64a of the outer tube 63 has a super-elastic metallic tube 62. The outer tube 63 covers the outer surface of the super-elastic metallic tube 62 and protrudes from its distal end to form a distal portion 64b. The super-elastic metallic tube 62 may extend to the distal end of the outer tube 63. The super-elastic metallic tube 62 is preferably formed of a super-elastic alloys such as a Ti-Ni alloys containing 49 ∼ 58 atom% of Ni, Cu-Zn alloys containing 38.5 ∼ 41.5 % by weight of Zn, Cu-Zn-X alloys containing 1 ∼ 10 % by weight of X wherein X is selected from the group consisting of Be, Si, Sn, Al and Ga, or Ni-Al alloys containing 36 ∼ 38 atom% of Al. The most preferred alloys are Ti-Ni alloys of the above composition. The super-elastic metallic tube 62 preferably has an outer diameter of 0.6 ∼ 2.0 mm, more preferably 0.8 ∼ 1.6 mm and a wall thickness of 40 ∼ 200 µm, more preferably 50 ∼ 150 µm. It preferably has a lengh of 300 ∼ 4,000 mm, more preferably 800 ∼ 3,000 mm a buckling strength (yield stress under load) of 5 ∼ 200 kg/mm² at 22°C, more preferably 8 ∼ 150 kg/mm² at 22°C, and a restoring stress (yield stress upon unloading) of 3 ∼ 180 kg/mm² at 22°C, more preferably 5 ∼ 130 kg/mm² at 22°C. The outer tube 63 preferably has an outer diameter of 0.60 ∼ 2.00 mm, more preferably 0.80 ∼ 1.60 mm and an inner diameter of 0.50 ∼ 1.90 mm preferably 0.60 ∼ 1.40 mm. The difference between the outer diameter of the inner tube 61 and the inner diameter of the outer tube 63 preferably is 0.05 ∼ 0.20 mm, more preferably 0.1 ∼ 1.20 mm and the wall thickness of the outer tube 63 is 0.05 ∼ 0.75 mm, more preferably 0.1 ∼ 0.3 mm.

The outer tube 63 is preferably formed of a somewhat flexible material and for the material, for example, thermoplastic resins such as polyolefin (e.g., polyethylene, polypropylene, ethylene-propylene copolymer), polyvinyl chloride, polyester, ethylene-vinyl acetate copolymer, polyamide elastomer and polyurethane and silicone rubber can be used. The above thermoplastic resins are preferred and polyolefins are more preferred.

The outer surface of the outer tube 63 may be coated with a biocompatible especially antithrombotic resin such as polyhydroxyethyl methacrylate or hydroxyethyl methacrylate-styrene copolymer (e.g., a HEMA-St-HEMA block copolymer).

The inner tube 61 is located inside the outer tube 63 and the distal portion of the inner tube 61 protrudes from the outer tube 63. The inner tube 61 preferably has an outer diameter of 0.40 ∼ 1.60 mm, more preferably 0.50 ∼ 1.30 mm and an inner diameter of 0.25 ∼ 1.50 mm, more preferably 0.30 ∼ 1.10 mm.

The inner tube 61 is preferably formed of a somewhat flexible material and for the material, for example, thermoplastic resins such as polyolefins (e.g., polyethylene, polypropylene, ethylene-propylene copolymer), polyvinyl chloride, polyester, ethylene-vinyl acetate copolymer, polyamide elastomer and polyurethane can be used. The above thermoplastic resins are preferred and polyolefins are more preferred.

The second lumen 67 is formed by the outer surface of the inner tube 61 and the inner surface of the outer tube 63. Therefore, the second lumen 67 has a sufficient volume. The tip of the second lumen 67 communicates with the internal space of the inflatable member 68 and the proximal end of the second lumen 67 communicates with the second opening 71 shown in Fig. 3 which forms an injection port for injecting a fluid (e.g., a contrast medium for angiography) for dilating the inflatable member 68. The second opening 71 is formed in the branched hub 70 shown in Fig. 3.

A super-elastic metallic tube may be disposed not on the outer tube 63 as in the catheter shown in Fig. 1. As illustrated on Fig. 2, the inner tube 61 may be provided with the super-elastic metallic tube 62. In such a case, the super-elastic metallic tube 62 may be disposed on the outer surface of the inner tube.

The inflatable member 68 is deflatable or foldable and can be folded around the inner tube 61. At least a part of the inflatable member 68 is an almost circular cylinder having an almost equal diameter so that a stenosis portion in a blood vessel can easily be dilated and the inflatable member 68 is foldable. The above almost circular cylindrical part may not be a completely circular cylinder and may be a polygonal cylinder. The rear end portion of the inflatable member 68 is liquid-tightly fixed to the distal portion of the outer tube 63 by adhesive bonding or thermal fusion and the tip portion of the inflatable member 68 is similarly liquid-tightly fixed to the distal portion of the inner tube 61. The inflatable member 68 forms an inflatable space between its inner surface and the outer surface of the inner tube 61. The rear end portion of the expansion space communicates with the second lumen 67 over the entire circumference. Therefore, since the second lumen 67 has a relatively large volume, the fluid for inflation can easily be injected into the inflatable member 68 through the second lumen.

The inflatable member 68 is preferably formed of a somewhat flexible material and for the material, for example, thermoplastic resins such as polyolefins (e.g., polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, cross-linked ethylene-vinyl acetate copolymer), polyvinyl chloride, polyester, polyamide elastomer and polyurethane, silicone rubber and latex rubber can be used. The above thermoplastic resins are preferred and cross-linked ethylene-vinyl acetate copolymer are more preferred. The inflatable member 68 during its inflation preferably has an outer diameter of the cylindrical part of 1.20 ∼ 35.00 mm, more preferably 1.50 ∼ 30.00 mm, a length of the cylindrical part of 10.00 ∼ 80.00 mm, more preferably 15.00 ∼ 75.00 mm and a total length of 15.00 ∼ 120.00 mm, more preferably 20.00 ∼ 100.00 mm.

Furthermore, in the catheter equipped with the inflatable member according to the present invention, it is preferred for facilitating the insertion into a blood vessel and further into a guide catheter to be mentioned later to apply hydrophilic treatment to areas having the possibility of contacting with blood during use, that is to say, the outer surface of the outer tube 63 and the outer surface of the inflatable member 68 so as to make them exhibit lubricity when contacted with blood or the like. Such hydrophilic treatments include coating with a hydrophilic polymer such as poly(2-hydroxyethyl methacrylate), polyhydroxyethyl acrylate, hydroxypropyl cellulose, methylvinyl ether-maleic anhydride copolymer, polyethylene glycol, polyacrylamide or polyvinyl pyrrolidone.

The branched hub 70 consists of an inner tube hub 73 which has the first opening 72 communicating with the first lumen 66 and constituting a guide wire port and is fixed to the inner tube 61 and an outer tube hub 74 which has the second opening 71 communicating with the second lumen and constituting an injection port for an inflating fluid and is fixed to the outer tube 63. The inner tube hub 73 and the outer tube hub 74 are fixed together.

The branched hub 70 is preferably formed of a thermoplastic resin such as polycarbonate, polyamide, polysulfone, polyallylate or methacrylate-butylene-styrene copolymer. Instead of providing such a branched hub 70, for example, a tube having a port member forming an opening at the proximal end may be liquid-tightly attached to each of the first and the second lumens.

Since the catheter of the present invention comprises an inner tube having a body portion, a distal portion and a first lumen whose tip is open; an outer tube which is disposed coaxially with said inner tube, has a body portion, a distal portion and a distal tip recessed by a predetermined distance from the distal tip of the inner tube and forms a second lumen between it and the outer surface of said inner tube; a deflatable or foldable inflating member which has a tip portion attached to the inner tube and a rear end portion attached to the outer tube and communicates with the second lumen near said rear end portion; a first opening disposed at the proximal end portion of said inner tube and communicating with the above first lumen; and a second opening disposed at the proximal end portion of the above outer tube and communicating with the second lumen and at least one of the body portions of the inner and outer tubes includes a super-elastic metallic tube. The catheter has a high efficiency of transmitting the pushing force given at its proximal end (pushability) and a high torque transmission efficiency. Furthermore, since the body portion of the catheter includes a super-elastic metallic tube, the wall thickness of the body portion can be made sufficiently thin and a catheter with a small diameter can be formed.