A catheter structure for use in medical treatment

Abstract: In a catheter structure having an inner tube, a metallic mesh knit provided to surround an outer surface of the inner tube and an outer tube provided to cover an outer surface of the metallic mesh knit, the metallic mesh knit is formed by spiral lines, one of which is greater than the other in mechanical strength.

Description: The invention relates to a catheter structure usually used for medical treatment to improve its manipulability. In a catheter structure which has an synthetic inner tube, a metallic mesh knit provided to surround an outer surface of the inner tube and an outer tube provided to cover an outer surface of the metallic mesh knit, the metallic mesh knit is made of flat thin wires of the same mechanical strength substantially knitted with equal pitch and angle. In this type of the catheter, it is difficult to concurrently overcome conflicting requirements between its structural property and functional property. When the thickness of the metallic mesh knit is reduced, its kink resistance property and good torque transmission is sacrificed although it better follows up a blood vessel due to an increased flexibility. When the thickness of the metallic mesh knit is increased, its follow-up property and inner diameter are reduced with less flexibility although the kink resistance property and good torque transmission are improved. With the reduced diameter of the metallic mesh knit, there arises a problem of increasing vessel pressure when supplying contrast medium with the blood vessel. When a guide catheter is used, there arises a problem of impeding passage of a balloon catheter and a stent. US 5,019,057 discloses a catheter structure in accordance with the preamble of claim 1. Therefore, it is an aim of the invention to provide a catheter structure which is capable of improving a kink resistant and good torque transmission property while maintaining a good follow-up property without reducing its inner diameter. Compared to US 5,019,057 the present invention is characterised by both the fibre or fibres of the one spiral line and the fibre or fibres of the other spiral line being rectangular in section, wherein the width of the fibre or fibres of the one spiral line being in the range of from 2.5 - 25 times that of the fibre or fibres of the other spiral line and the thickness of the fibre or fibres of the one spiral line being 1.0 - 10 times that of the fibre or fibres of the other spiral line; the fibre or fibres of the one spiral line being greater than the fibre or fibres of the other spiral line in hardness; and the fibre or fibres of the one spiral line being greater than the fibre or fibres of the other spiral line in terms of geometrical moment of inertia. Further optional features of the invention are set out in the dependent claims appended hereto. These, together with other aims, features and advantages which will be further described hereinafter with reference to exemplary embodiments and the accompanying drawings, in which: Fig. 1a is a perspective view of a catheter structure according to an embodiment of the invention; Fig. 1b is an enlarged perspective view of a main part of the catheter structure taken along the line A-A of Fig. 1a but partly removed; and Figs 2a-2d are sequential views of the main part of the catheter structure showing how the catheter is assembled. Referring to Fig. 1a, a catheter 1 has a catheter body 10 and a grip 11 provided at a rear portion of the catheter body 10. To a front end surface of the catheter body 10 which is made of a flexible tube, a soft tip 12 is connected. As shown in an enlarged view in Fig. 1b, the catheter body 10 has an inner tube 2 made of a synthetic resin. An outer surface of the inner tube is surrounded by a metallic mesh knit 3 which is coated by an outer tube 4 made of a synthetic resin. The metallic mesh knit 3 comprises a series of counterclockwise spiral lines and a series of clockwise spiral lines 6. The spiral line 5 is adapted to be mechanically stronger than another spiral line 6 in the following manner. The spiral line 5 includes eight thin fibres 51, each of which is flatly compressed into sash-like structure which measures 0.26 mm in width and 0.06 mm in thickness. Each of the thin fibers 51 is originally made of a stainless steel wire which measures 0.12 mm in diameter. In this instance, the stainless steel wire of the thin fiber 51 is usable so long as its diameter is below 0.2 mm with its Vicker's hardness (Hv) ranging from 180 to 750. It is preferable that the compressed thin fiber 51 measure 0.05 mm - 0.50 mm in width and 0.01 mm - 0.10 mm in thickness. The number of the thin fibers 51 can be altered appropriately within the range of 1 - 24. On the other hand, another spiral line 6 includes eight thin fibers 61, each of which is flatly compressed into sash-like structure which measures 0.13 mm in width and 0.03 mm in thickness. Each of the thin fibres 61 is originally made of an annealed stainless steel wire which measures 0.07 mm in diameter. In this instance, the stainless steel wire of the thin fiber 61 is usable so long as its diameter ranges from 0.04 mm to 0.12 mm with its Vicker's hardness (Hv) ranging from 50 to 210. It is preferable that the thin fiber 61 measures 0.02 mm - 0.20 mm in width and 0.01 mm - 0.10 mm in thickness. The number of the thin fibers 51 can be altered appropriately within the range of 1 - 24. The method of manufacturing the catheter 1 is as follows: (1) The inner tube 2 is made by extruding or blowing the synthetic resin over an outer surface of a metallic core 1A as shown in Fig. 2a. (2) On the outer surface of the inner tube 2, the eight numbers of thin fibers 51 and the thin fibers 61 are knitted together to form the metallic mesh knit 3 as shown in Fig. 2b. (3) After knitting the thin fibers 51, 61, the thin fiber 61 is yieldingly bent to form a hook portion against another thin fiber 51 at each of the intersection of the thin fibers 51, 61. (4) The outer tube 4 is made by extruding or blowing the synthetic resin over the outer surface of the metallic mesh knit 3 as shown in Fig. 2c. (5) The metallic core 1A is axially stretched to reduce its diametrical dimension, and the core 1A is pulled out of the inner tube 2 as shown in Fig. 2d. With the thin fiber 61 yieldingly bent against another thin fiber 51, the thin fiber 61 entangles with another thin fiber 51 so as to increase the mechanical strength of the metallic mesh knit 3. This makes it possible for the catheter to favorably follow up the blood vessel while maintaining a good kink resistant and torque transmission property. In the foregoing embodiment of the invention, the cross sectional area and the hardness are discretionally altered to provide the difference of the mechanical strength between the two types of the thin fiber 51, 61, the difference of the mechanical strength may be added as follows: (a) Instead of the annealed stainless steel, the thin fiber 61 of the spiral line 6 may be made by polyamide, polypropylene or the like. (b) In the method of manufacturing the catheter, a step of compressing the metallic mesh knit 3 is not always necessary. Without compressing the metallic mesh knit, the thin fiber 61 is yieldingly bent against the thin fiber 51 at their intersection, thus substantially improving the kink resistant and torque transmission property. While the invention has been described with reference to the specific embodiments, it is understood that this description Is not to be construed in a limiting sense in as much as various modifications and additions to the specific embodiments may be made by skilled artisan without departing from the scope of the invention, as defined in the appended claims.

Claims: A catheter structure comprising: an inner tube (2); an at least partially metallic mesh knit (3) surrounding an outer surface of the inner tube (2), and an outer tube (4) covering an outer surface of the metallic mesh knit (3); wherein the metallic mesh knit (5) is formed by two spiral lines (5, 6) one of which is greater than the other in mechanical strength, each of said spiral lines (5, 6) comprises a single thin fibre or a plurality of thin fibres, the fibre or fibres of the one spiral line (5) being greater in cross section than the fibre or fibres of the other spiral line (6); characterised by both the fibre or fibres of the one spiral line and the fibre or fibres (51) of the other spiral line being rectangular in section, wherein the width of the fibre or fibres of the one spiral line (5) being in the range of from 2.5 - 25 times that of the fibre or fibres (61) of the other spiral line (6) and the thickness of the fibre or fibres (51) of the one spiral line (5) being 1.0 - 10 times that of the fibre or fibres (61) of the other spiral line (6); the fibre or fibres of the one spiral line being greater than the fibre or fibres (61) of the other spiral line (6) in hardness; and the fibre or fibres (51) of the one spiral line (5) being greater than the fibre or fibres (61) of the other spiral line (6) in terms of geometrical moment of inertia. A catheter structure according to claim 1, wherein the one spiral line (5, 6) is made of stainless steel, and the other spiral line is made of synthetic resin. A catheter structure according to claim 1 or 2, wherein each of the two spiral lines (5, 6) is comprised of a plurality of thin fibres, where a cross section of the fibres of one spiral line is substantially the same as that of the fibres of the other spiral line, and the number of the plurality of thin fibres of the one spiral line is greater than that of the other spiral line. A catheter structure according to claim 1, wherein the number of the plurality of thin fibres of the one spiral line is in the range of from 1 to 24. A catheter structure according to claim 1, the fibre or fibres of the one spiral line have dimensions in the range of 0.05 to 0.50 mm in width and 0.01 to 0.10 mm in thickness and the fibre or fibres of the other spiral line have dimensions in the range of 0.02 to 0.20 mm in width and 0.01 to 0.10 mm in thickness. A catheter structure according to claim 1, wherein each of the two spiral lines is made of stainless steel.

Inventors: KATO TADAKAZU, MIYATA KENJI, MIZUKAMI ISAMU, KATO, TADAKAZU, MIYATA, KENJI, MIZUKAMI, ISAMU
Applicants: ASAHI INTECC CO LTD, ASAHI INTECC CO., LTD.
Application year: 1996
Main classification: A61M25
IPC codes: A61M25