WO2010060889A1

WO2010060889A1 - Microcatheter

Info

Publication number: WO2010060889A1
Application number: PCT/EP2009/065690
Authority: WO
Inventors: Ronald Adrianus Maria Horvers
Original assignee: Blue Medical Devices Bv
Priority date: 2008-11-26
Filing date: 2009-11-24
Publication date: 2010-06-03

Abstract

The application relates to a single lumen, balloonless catheter (100) having a proximal end (20) and a distal end (10), comprising an elongated flexible shaft (30) disposed with a longitudinal guidewire lumen (32) extending therein, which shaft (30) is connected at its distal end to a flexible distal tip (74) through which the guidewire lumen (32) extends, the flexible distal tip (74) formed from a solid-walled hollow cylinder of polymeric material, the shaft (30) comprising a hollow rope tube (72) formed from a plurality of longitudinal wire cables (40, 40') cylindrically stranded to form the hollow rope tube (72), the hollow rope tube (72) optionally having a region of transitional flexibility between the proximal (20) and distal ends (10).

Description

MICROCATHETER

FIELD OF THE INVENTION

This invention relates to a catheter (known herein as a microcatheter) having a narrow profile and flexible distal tip which provides good pushability and torque transfer, and is especially suited for guidewire support and exchange. More particularly, the invention relates to an over-the-wire microcatheter comprising a shaft formed from a hollow rope tube optionally disposed with a stiff proximal end, a flexible distal end, a region of transitional flexibility there between, and provided with a flexible distal tip, that improves the passage of the guidewire through the catheter.

BACKGROUND TO THE INVENTION

The use of catheters to treat structures, stenoses, or narrowings in various parts of the human body is well known in the prior art. Examples of such catheters are shown in Bonzel U.S. Pat. No. 4,762,129, Yock U.S. Pat. No. 5,040,548, Kanesaka U.S. Pat. No. 5,330,499, Solar U.S. Pat. No. 5,413,557, Tsukashima et al. U.S. Pat. No. 5,458,639, US 2008/0287786, WO 2006/065926, EP 1 428 547, EP 1 243 283, and WO 2006/122243.

In many cases, a stent must be implanted to provide permanent support for the artery. When a stent is to be implanted, it is usual practice to first advance a guidewire along the vasculature to the stenosed region, along which a stent bearing balloon catheter can later be guided. It is a problem that, not only are regions of the vasculature tortuous, but may be partially occluded which prevent proper access to the site of treatment.

After a first guidewire has been placed in the patient, the physician may wish to remove that guidewire and replace it with another guidewire having a different diameter or other property. It is a further problem in the art to replace an existing guidewire without loss of ideal placement when the vicinity of the guidewire distal end is located in a narrowed vasculature region.

Over the wire catheters employ a long guidewire lumen from the distal end to the top. As known in the art, the guidewire lumen of an over the wire catheter may be a duct at least partly reinforced with a hypotube as described in US 7,166,1 10 B2. The proximal portion of the catheter reinforced by the hypotube may have much greater column strength, which will tend to enhance the pushability of the catheter. The distal end also reinforced by hypotube disposed with a smaller distal pitch provides increased flexibility compared with the proximal end, which assists with advances through curves and crossing junctions. The skilled practitioner understands that a catheter will have an optimum combination of performance characteristics, which may be selected among: flexibility, pushability, catheter trackability, guidewire trackability, low profile, torque transfer and others. Flexibility may relate to bending stiffness of a catheter and/or stent, in a particular region or over its entire length. Pushability may relate to the column strength of a device or system along a selected path. Catheter trackability may refer to a capability of a catheter to successfully follow a desired path in a vessel, for example without prolapse. Guidewire trackability may refer to the ability of the catheter to advance along the guidewire, offering minimal resistance. Profile may refer to a maximum transverse dimension of the catheter, at any point along its length. Torque transfer refers to the ability of a catheter to transfer a rotational force from the proximal (handling) end to the distal end.

A disadvantage of some catheters in the art is their guidewire trackability that is reduced by the use of hypotubing. Said tubing creating a series of transverse circular ridges within the guidewire lumen that frictionally engage with the guidewire and prevent its advancement. Guidewire passage is particularly hindered when the catheter is bent so exposing gaps between the hypotube spiral into which a guidewire tip can enter and lodge. The guidewire then needs to be withdrawn and an attempt made to re-advance it through the guidewire lumen.

A further disadvantage of catheters in the art is their low torque transfer. During catheter advancement through a tortuous vasculature, a rotation of the catheter at the proximal end can be effective in opening vessels directing the tip of the catheter in a different direction. In addition catheters of the art having guidewire lumens formed substantially from polymeric material, exhibit undesirable frictional contact with the guidewire. When a long catheter is advanced along a long guidewire, the frictional effect can substantially hinder movements of the catheter, and the surgeon may experience difficulties with making fine adjustments.

A still further disadvantage of catheters of the art is their difficulty of manufacture. When a hypotubing requires rendering watertight by way of a jacket, the jacket must be manually applied in or over the hypotubing which, owing to the presence of near-transverse spiral cuts, can lead to the leading end of the jacket becoming engaged in the spiral cuts, thereby preventing its smooth passage over the hypotubing. In view of the foregoing, it is an object of this invention to provide improved catheters for use with guide wires. In particular, the present invention aims to provide a catheter having differential flexibility at the distal and proximal ends, excellent guidewire trackability and torque transfer, while still maintaining good pushability and catheter trackability. These and various other objects, advantages and features of the present invention will become apparent from the following description and claims, when considered in conjunction with the appended drawings.

SUMMARY OF THE INVENTION One embodiment of the invention is a catheter (100) having a proximal end (20) and a distal end (10), comprising an elongated flexible shaft (30) disposed with a longitudinal guidewire lumen (32) extending therein, which shaft (30) is connected at its distal end to a flexible distal tip (74) through which the guidewire lumen (32) extends, the shaft (30) comprising a hollow rope tube (72) formed from a plurality of longitudinal wire cables (40, 40') cylindrically stranded to form the hollow rope tube (72), the hollow rope tube (72) optionally having a region of transitional flexibility between the proximal (20) and distal ends (10). The catheter is preferably a single lumen catheter. It is preferably a balloonless catheter. The flexible distal tip (74) is preferably formed from a solid-walled hollow cylinder of polymeric material,

Another embodiment of the invention is a catheter as described above, wherein the hollow rope tube (72) has a region of transitional flexibility, and the outer diameter of the hollow rope tube (72) gradually decreases in a direction from the proximal end (20) to the distal end (10) in the region of transitional flexibility.

Another embodiment of the invention is a catheter as described above, wherein the hollow rope tube (72) is provided with a medium impermeable coating or outer jacket.

Another embodiment of the invention is a catheter as described above, wherein the hollow rope tube (72) has a region of transitional flexibility, and the thickness of the coating or outer jacket gradually decreases in a direction from the proximal end (20) to the distal end (10) in the region of transitional flexibility.

Another embodiment of the invention is a catheter as described above, further comprising a coupling at the terminus of the proximal end (20) for connection of the guidewire lumen (32) to a source of pressurized fluid. Another embodiment of the invention is a catheter as described above, further comprising one or more radiopaque marker configured to indicate the position of the catheter in a subject.

Another embodiment of the invention is a catheter as described above, wherein the hollow rope tube (72) is formed by cylindrically stranding a group of metallic wire cables (40, 40') along a predetermined circle line to provide the tube (72) of the invention. The metallic wire cables are preferably formed from stainless steel.

Another embodiment of the invention is a catheter as described above, wherein the interior surface (25) of the guidewire lumen (32) is coated with either high and/or low density polyethylene, polyamides, poly(ethylene terephthalate) (PET) or polyesters and copolymers thereof, teflon or any such material that comprises a hydrophilic and/ or reduced surface friction character.

Another embodiment of the invention is a catheter as described above, wherein the exterior surface of the catheter (100) is coated with either high and/or low density polyethylene, polyamides, poly(ethylene terephthalate) (PET) or polyesters and copolymers thereof, teflon or any such material that comprises a hydrophilic and/ or reduced surface friction character.

Another embodiment of the invention is a catheter as described above, wherein flexible distal tip (74) is made or formed essentially from nylon, polyamide, silicone rubber, polypropylene, polyethylene, polyurethanes, poly(ethylene terephthalate) (PET), polyesters and copolymers thereof.

Another embodiment of the invention is a catheter as described above, wherein the maximum diameter of the shaft (30) is between 0.5 mm and 0.7 mm.

Another embodiment of the invention is a catheter as described above, wherein the maximum diameter of the distal tip (74) is between 0.4 mm and 0.7 mm.

DETAILED DESCRIPTION OF THE FIGURES FIG. 1 is a schematic illustration of a microcatheter of the invention comprising a hollow rope shaft having differential regions of flexibility (S-, T- and F- regions), disposed with a flexible distal tip. FIG. 2 is a transverse (D-D) cross-section through the distal tip of a microcatheter as shown in FIG. 1 , whereby the wall is formed from a continuous hollow cylinder.

FIG. 3A is a transverse (A-A) cross-section through the S-region of a microcatheter as shown in FIG. 1 , whereby the cables of the hollow rope shaft have a circular profile, and the shaft is devoid of coating or jacket.

FIG. 3B is a transverse (B-B) cross-section through the T-region of a microcatheter as shown in FIG. 1 , whereby the cables of the guidewire duct have a part-circular profile, and the shaft is devoid of coating or jacket.

FIG. 3C is a transverse (C-C) cross-section through the F-region of a microcatheter as shown in FIG. 1 , whereby the cables of the guidewire duct have a semi-circular profile, and the shaft is devoid of coating or jacket.

FIG. 4A is a transverse (A-A) cross-section through the S-region of a microcatheter as shown in FIG. 1 , whereby the cables of the guidewire duct have a circular profile, and the shaft has a coating of constant thickness. FIG. 4B is a transverse (B-B) cross-section through the T-region of a microcatheter as shown in FIG. 1 , whereby the cables of the guidewire duct have a part-circular profile, and the shaft has a coating of constant thickness.

FIG. 4C is a transverse (C-C) cross-section through the F-region of a microcatheter as shown in FIG. 1 , whereby the cables of the guidewire duct have a semi-circular profile, and the shaft has a coating of constant thickness.

FIG. 5A is a transverse (A-A) cross-section through the S-region of a microcatheter as shown in FIG. 1 , whereby the cables of the guidewire duct have a circular profile, and the shaft has a coating that is thickest in the S-region.

FIG. 5B is a transverse (B-B) cross-section through the T-region of a microcatheter as shown in FIG. 1 , whereby the cables of the guidewire duct have a circular profile, and the shaft has a coating that is intermediate thickness in the T-region.

FIG. 5C is a transverse (C-C) cross-section through the F-region of a microcatheter as shown in FIG. 1 , whereby the cables of the guidewire duct have a circular profile, and the shaft has a coating that is thinnest in the F-region. FIG. 6 is a transverse cross-section through a microcatheter as shown in FIG. 1 (e.g. across A-A, B-B, or C-C), indicating the dimensions of the shaft.

FIG. 7 is a transverse cross-section through a catheter as shown in FIG. 1 (e.g. across D-

D), indicating the dimensions of the distal tip.

FIG. 8 is an illustration of the apparatus used to prepare a hollow rope shaft of the present invention. DETAILED DESCRIPTION OF THE INVENTION

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as is commonly understood by one of skill in the art. All publications referenced herein are incorporated by reference thereto. All United States patents and patent applications referenced herein are incorporated by reference herein in their entirety including the drawings.

The articles "a" and "an" are used herein to refer to one or to more than one, i.e. to at least one of the grammatical object of the article. The recitation of numerical ranges by endpoints includes all integer numbers and, where appropriate, fractions subsumed within that range (e.g. 1 to 5 can include 1 , 2, 3, 4 when referring to, for example, a number of articles, and can also include 1.5, 2, 2.75 and 3.80, when referring to, for example, measurements). The recitation of end points also includes the end point values themselves (e.g. from 1.0 to 5.0 includes both 1.0 and 5.0).

The present invention concerns a microcatheter having a proximal end and distal end, comprising a longitudinal shaft with a guidewire lumen extending therewithin. The longitudinal shaft terminates at the distal end with a flexible distal tip, through which the guidewire lumen also extends. Being a microcatheter, it is preferably devoid of an inflatable balloon, i.e. it is balloonless.

The longitudinal shaft comprises a hollow rope tubing formed from a plurality of longitudinal wire cables cylindrically stranded to form the hollow rope tubing wherein the distal end is more flexible than the proximal end, and a region of transitional flexibility connects the differentially flexible ends. Advantageously, the hollow rope tubing so formed facilitates the ease of passage of the guidewire, since the cables forming the hollow rope tubing lumen run in a longitudinal direction. As mentioned elsewhere, advancement of a catheter of the art over a guidewire, can be difficult due to the guidewire frictionally engaging with the guidewire lumen. Because the guidewire lumen is provided with a plurality of essentially longitudinal grooves in the present invention, the proximal end of the guidewire is actively guided in the longitudinal direction. Moreover, the cylindrical cables presents a plurality of convex surfaces which direct the guidewire away from the inner wall, compared with a concave surface of traditional catheters which contribute to passage of a guidewire into the inner wall, particularly at bends. In additional, the duct so formed exhibits excellent torque transfer in both rotational (clockwise and anti-clockwise) directions. The flexibility of the hollow rope tubing may be uniform from its proximal end to its distal end, which may be achieved with a uniform duct diameter or wall thickness. Alternatively, it may gradually change from the proximal end to the distal end, typically being more stiff at the proximal end so as to provide better pushability. The more flexible distal end facilitates advancement of the catheter tip through the tortuous route of the vasculature. The longitudinal disposition of the cables also facilitates covering with a jacket, which can be slid over or in the hollow rope tubing with ease. Extending the distal end of the hollow rope tubing with a flexible distal tip provides additional flexibility at the distal end, useful for passage through severely convoluted routes. The length of the distal tip can be determined by requirements of the procedure according to the requirements of the intervention.

Because the microcatheter of the present invention has a narrow profile, it is able to pass through narrow vasculature easily, and yet it exhibits exceptional pushability and torque transmission from the proximal end to the distal tip. The pushing and rotational forces are transferred to the distal tip, which are capable of opening passages blocked by depositions. The ability to transmit a torque permits a rotation at the distal tip, that has an action capable of prising open occluded regions, and partially removing material causing the blockage. Because the distal tip is polymeric, it is softer and more flexible that a tip formed from hollow rope tubing, which polymeric tip prevents cutting of the occlusion, so generating less debris than a tip formed from hollow rope tubing. In particular, the microcatheter may provide guidewire support i.e. may accommodate a guidewire in its lumen and facilitate the crossing of regions partially blocked by hardened calcium deposits.

The microcatheter may also be employed to penetrate a blockage in a vessel by iterative cycles of guidewire and microcatheter advancement. The method described in detail below efficiently combines the excellent pushability and torque transfer of the microcatheter with the ability of the guidewire itself to apply a strong mechanical force to the blockage from its distal terminal end.

The microcatheter of the invention also finds utility in in situ guidewire exchange. Owing to its narrow profile, the microcatheter can be advanced in an over-the-wire mode to the point in the vasculature where the distal end of the guidewire rests. The in-place guidewire is withdrawn through the guidewire lumen and out through the proximal guidewire port of the microcatheter. The replacement guidewire is inserted through the proximal guidewire port of the microcatheter and along the guidewire lumen and out through the distal guidewire port. Since the distal guidewire port is in the same location as the original guidewire's distal terminal end or the vicinity thereof, the distal end of the replacement guidewire finds the same location in the vasculature.

The microcatheter may also be applied in a retrograde approach to unblock a vascular and facilitate in guidewire placement; by virtue of its flexibility, particularly by virtue of the flexible distal tip, the microcatheter is able to loop around a blockage and approach it from an alternative direction, thereby loosening and breaking down the blockage, as elaborated below. The microcatheter of the invention also be used to deliver medicament to the site of treatment.

Reference is made in the description below to the drawings which exemplify particular embodiments of the invention; they are not at all intended to be limiting. The skilled person may adapt the device and substitute components and features according to the common practices of the person skilled in the art.

With reference to FIG. 1 , one embodiment of the present invention concerns a microcatheter 100 comprising an elongated flexible shaft 30 having a proximal end 20, a distal end 10, a longitudinal guidewire lumen 32 disposed within the shaft 30. The catheter is preferably balloonless. The distal end of the elongated flexible shaft 30 terminates in a flexible distal tip 74, through which the guidewire lumen 32 (FIGs. 6, 7) extends. The guidewire lumen 32 is in fluid connection with a distal guidewire port 33 located at the distal end 10 of the microcatheter 100, and also in fluid communication with a proximal guidewire port 35 located at the proximal end 20 of the microcatheter 100. The shaft is formed at least partially from a hollow rope tube 72 comprising a plurality of longitudinal wire cables 40, 40' (FIGs. 3A, 4A, 5A) cylindrically stranded to form the hollow rope tube 72 optionally having a region of transitional flexibility between its proximal 20 and distal ends 10.

The terms "distal", "distal end", "proximal" and "proximal end" are used through the specification, and are terms generally understood in the field to mean towards (proximal) or away (distal) from the surgeon side of the apparatus. Thus, "proximal (end)" means towards the surgeon side and, therefore, away from the patient side. Conversely, "distal (end)" means towards the patient side and, therefore, away from the surgeon side.

The microcatheter 100 comprises an elongated shaft 30 (also referred to as a shaft herein) having with a proximal end 20 and a distal end 10, and a guidewire lumen 32 therein which extends the longitudinal length of the shaft 30. The proximal 20 terminal end of the guidewire lumen 32 is open (not sealed) for the passage of guidewire, and optionally of fluidic substances such as medicament. In a preferred embodiment of the invention, the catheter guidewire lumen 32 is the sole lumen e.g. there may be no inflation lumen nor separate medicament delivery lumen. The distal end 10 of elongated shaft 30 is connected to a distal tip 74, through which the guidewire lumen extends. The elongated shaft 30 is typically cylindrical. It will be appreciated that the elongated shaft 30 and distal tip 74 utilize an essentially co-axial assembly.

Hollow rope tube The elongated shaft 30 is formed, at least partially, from a hollow wire-cable rope tube 72. The hollow rope tube 72 is made by cylindrically stranding a group of wires along a predetermined circle line to provide a hollow rope tube 72 of the invention. An inner surface 25 of the hollow rope tube 72 forms a plurality of concave structures represented by the wires 40, 40' that are circular in cross-section. Such tubing is known in the art, for example, the Actone cable tube as manufactured by Asahi Intecc, and described, for instance, in US 2004/0249277 and EP 1 902 745. An outer surface 27 of the hollow rope tube 72 may be rendered partially smooth in regions of increased flexibility giving rise to wires 40, 40' that are part or semi-circular, while the inner surface forms a guidewire lumen 32 in which the convex-concave structure resides.

The hollow rope tube 72 may have 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 , 12, 13, 14, 15, 16, 17, 18, 19, 20, 21 , 22, 23 or 24 metallic wires 40, 40', or a number in the range between any two of the aforementioned values, preferably between 2 and 24. The wires 40, 40' are preferably metallic as describe herein. The wires 40, 40' may be formed from stainless steel or nitinol.

The maximum outer diameter (ROD, FIG. 6) of the hollow rope tube 72 including any coating or jacket, may be equal to or no greater than 0.50 mm, 0.55 mm, 0.6 mm, 0.65 mm, 0.70 mm, 0.80 mm, 0.90 mm, 1.0 mm, 1.2 mm, or a value in the range between any two of the aforementioned values, preferably between 0.5 mm and 0.6 mm. The maximum inner diameter (RID, FIG. 6) of the hollow rope tube 72 may be equal to or no greater than 0.30 mm, 0.35 mm, 0.40 mm, 0.45 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm or a value in the range between any two of the aforementioned values, preferably between 0.3mm and 0.5 mm.

The hollow rope tube 72 may be manufactured according to a scheme as shown in FIG. 8. Namely, a wire rope R is provided by stranding the metallic wires 40, 40' around an elongated core (not shown). One end of the wire rope R is secured to a rotational chuck

61 of a twisting device 70. The other end of the wire rope R is secured to a slidable chuck 63 from which a weight 67 is attached applying a longitudinal force. The wire rope R is twisted under the tensile force applied by the weight 67. A current generating device 68 provides electric currents to the chucks 61 and 63 through an electric wire 64 so that the wire rope R is heated by its electric resistance to remove the residual stress appeared on the wire rope R during the twisting process. Once the rope has formed, the outer surface of the hollow rope tube 72 may be smoothly ground to provide the requisite flexibility as necessary so that the metallic wires 40, 40' have a semi- or part-circular cross-section in the flexible regions. The elongated core is withdrawn from the wire rope R to provide a hollow tube structure that is the hollow rope tube 72.

The hollow rope tube 72 has an inherent medium-impermeable property, however, it may rendered medium-impermeable at higher pressures, for instance upto 30 bar by a medium-impermeable coating or jacket. The hollow rope tube 72 formed from the plurality of wire cables may be provided with a jacket or coating 51 , 52, 54, 56 (FIGs. 4A to 4C; FIGs. 5A to 5C) made from a substance typically used to form lumens in corresponding catheters of the art. For example, the jacket or coating may comprise of high and/or low density polyethylene, polyamides, poly(ethylene terephthalate) (PET) or polyesters and copolymers thereof, teflon or any such material that comprises a hydrophilic character. The coating or jacket improves the medium-impermeable property of the hollow rope tube 72. In the case of a coating, it can be applied by spraying or dipping a liquid form of the polymer over the surface of the duct. In the case of a jacket, it may be in slid in or over the hollow rope tube 72; advantageously, the longitudinal disposition of the cables facilitates sliding of the jacket. It is within the scope of the invention, that the coating is applied on the outside and/or the inside surface(s) of the duct. The interior surface 25 of the hollow rope tube 72 may be Teflon coated.

The flexible hollow rope tube 72 of the invention may have a region of transitional flexibility between its proximal 20 and distal ends 10 as mentioned elsewhere. The region provides a gradually changing flexibility from a stiffer proximal end to a less stiff (more flexible) distal end, thereby imparting differential flexibility on the guidewire duct.

The outer diameter (ROD) of the hollow rope tube 72 may gradually decrease in a direction from the proximal end 20 to the distal end 10 in the region of transitional flexibility. Proximal 20 to the region of transitional flexibility, the outer diameter of the hollow rope tube 72 may be essentially constant and essentially equal to the largest diameter present in the region of transitional flexibility. Distal 10 to the region of transitional flexibility, the outer diameter of the hollow rope tube 72 may be essentially constant and essentially equal to the smallest diameter present in the region of transitional flexibility. The inner diameter (RID) of the hollow rope tube 72 remains constant along the length of the hollow rope tube 72.

The distal end 10 of the hollow rope tube 72 may have a section in the lengthwise direction known herein as a flexible (F) region, depicted in FIG. 1. The proximal end 20 of the hollow rope tube 72 may have a section in the lengthwise direction that belongs to the stiff (S) region as known herein. The hollow rope tube 72 in the F-region exhibits greater flexibility compared with the hollow rope tube 72 in the S-region. A lengthwise portion, the transition (T) region, between the F-region and S-region serves as a region of transitional flexibility between the F-region and S-region. The S-region provides the requisite pushability to advance the microcatheter from the proximal end 20 without kinking the catheter, while the F-region being more flexible, can bend and flex around the tortuous route of a vasculature. The T-region effectively buffers the movements between the F- region and S-region.

The flexibility of the hollow rope tube 72 in the F-region may be increased compared with that in the S-region by a diametric reduction of the hollow rope tube 72. A lengthwise portion, the T-region, may be between the F-region and S-region diametrically increases progressively from distal 10 to the proximal 20 end to serve as a region of transitional flexibility between the F-region and S-region. As shown in FIGS. 3A, 3B and 3C the outer diameter of the tube, ROD, is maximal in the S-region (FIG. 3A), minimal in the F-region (FIG. 3C) and is transitional in the T-region (FIG. 3B). It will be appreciated that the cross- sections in the T-region progressive increase in diameter from the distal to proximal end. The smaller outer diameter, ROD, combined with a constant internal diameter, RID, provide a thinner wall in the F-region exhibiting increased flexibility compared with the thicker walled tube 72 in the S-region. The outer diameter of the hollow rope tube 72 may be modified by chemical treating or deforming or grinding the outside surface, for instance the metallic wires 40, 40' have a circular form in cross section with its outer surface not ground in the S-region (FIG. 3A), compared with in the F-region where the ground wires adopt a semi-circular profile (FIG. 3C).

The minimum outer diameter (ROD) of the hollow rope tube 72 in the F-region, may be 100%, 98 %, 96 %, 95 %, 90 %, 85 %, 80 %, 75 %, 70 % of that of the maximum outer diameter (ROD) of the hollow rope tube 72 in the S-region. The maximum outer diameter (ROD) of the hollow rope tube 72 in the S-region, may be equal to or no greater than 0.50 mm, 0.55 mm, 0.60 mm, 0.65 mm, 0.70 mm, 0.80 mm, 0.90 mm, 1.0 mm, 1.2 mm, or a value in the range between any two of the aforementioned values, preferably between 0.5 mm and 0.7 mm.

According to an aspect of the invention, the hollow rope tube 72 may be provided with a polymeric coating or jacket. The purpose of the jacket may be to provide or enhance medium impermeability. Where the differently flexible regions are provided by diametric changes in the hollow rope tube 72, the thickness of the jacket or coating may be constant as shown in FIGs. 4A, 4B and 4C, where the minimum coating 51 thickness is the same in the S-region (FIG. 4A), T-region (FIG. 4B) and F-region (FIG. 4C). In such cases, the jacket or coating thickness does not contribute to differential flexibility.

According to another aspect of the invention, the hollow rope tube 72 may be provided with a polymeric coating or jacket which thickness varies according to the desired flexibility. The purpose of the jacket may be to add or enhance medium impermeability, but also to control flexibility. In such cases, the diameter of the hollow rope tube 72 may be constant, and differential flexibility is achieved by virtue of the coating or jacket only.

The thickness of the coating or jacket only may gradually decrease in a direction from the proximal end 20 to the distal end 10 in the region of transitional flexibility. Proximal 20 to the region of transitional flexibility, the minimum thickness of the coating or jacket may be essentially constant and essentially equal to the largest thickness present in the region of transitional flexibility. Distal 10 to the region of transitional flexibility, the thickness of the coating or jacket may be essentially constant and essentially equal to the smallest thickness present in the region of transitional flexibility. The inner diameter (RID) of the hollow rope tube 72 remains constant along the length of the hollow rope tube 72; and outer diameter (ROD) preferably remains constant, or may vary to further enhance differential flexibility.

Depicted in FIG. 5A to 5C is the instance where the rope formed by the metallic strands has a constant diameter, the thickness of the coating 52 in the S-region (FIG. 5A) is greater compared with in the F-region (FIG. 5C) and the section is accordingly stiffen T- region exhibits a transition thickness at the section indicated (FIG. 5B). According to one aspect of the invention, differential flexibility may be enhanced by combining both diametric changes in hollow rope tube 72 with variable coating or jacket thicknesses. The minimum thickness of the coating or jacket of hollow rope tube 72 in the F-region, may be equal to or no more than 100%, 98 %, 96 %, 95 %, 90 %, 85 %, 80 %, 75 %, 70 % of the thickness of the coating or jacket in the S-region. The maximum thickness of the coating or jacket in the S-region may be equal to or no greater than 0.01 mm, 0.05 mm, 0.1 mm, 0.4 mm, or a value in the range between any two of the aforementioned values, preferably between 0.01 mm and 0.2 mm.

Other ways to achieve a variation in flexibility includes differentially tempering the metal during formation of the rope, changing the weight applied during the stranding process, changing the diameter of the elongated cored used during stranding, changing the type of metal used during stranding.

The length of the F-region, may be 0%, 2%, 5%, 10 %, 20 %, 30 %, or 40 % of the length of the catheter or a value in the range between any two of the aforementioned values, preferably between 2 and 30%.

The length of the T-region, may be 0%, 2%, 5 %, 10 %, 15%, or 20 %, of the length of the catheter or a value in the range between any two of the aforementioned values, preferably between 2 and 20%.

The length of the S-region, may be 40 %, 55 %, 60 %, 65 %, 70 %, 80%, 85%, 90%, 95% or 100% of the length of the catheter or a value in the range between any two of the aforementioned values, preferably between 70 and 95%.

The overall length of the microcatheter 100 is typically about 60 cm to about 200 cm. The exterior surface of the microcatheter 100 may be coated.

Flexible tip

The distal end 10 of the flexible shaft 30 is connected to a flexible distal tip 74 as shown, for instance, in FIG. 1. The guidewire lumen 32 extends through the distal tip 74. The longitudinal axes of the tip 74 and of the flexible shaft 30 are preferably in co-axial alignment. The distal guidewire port 33 is disposed on the distal tip 74 at the distal end, while the proximal guidewire port 35 is disposed on the shaft 30 at the proximal end. The distal guidewire port 33 is preferably disposed on the distal tip 74 at the distal terminal end, while the proximal guidewire port 35 is disposed on the shaft 30 at the proximal terminal end. The distal tip 74 is disposed with a guidewire lumen extending the length of the distal tip 74. The guidewire lumen of the flexible shaft 30 and the guidewire lumen of the distal tip 33 are in fluid communication and their longitudinal axis are preferably aligned coaxially. The distal tip is preferably a continuous cylinder; it may be tapered at the distal end. It is preferably devoid of ports, other than the distal guidewire port.

The distal tip 74 may be attached to the hollow rope tube 72 using any suitable attachment means in the art, for instance, by way of a frictional joint e.g. a portion of the proximal end 20 of the distal tip 74 disposed over a portion of the distal end of the hollow rope tube 72. Other means include the use of adhesive, or an inline adaptor (e.g. portion of bridging tubing) that mates one end of the hollow rope tube 72 with one end of the distal tip 74. Other means include the use of heat bonding.

Distal tip 74, generally will be more flexible than the hollow rope tube 72 or the hollow rope tube in the F-region where present. The length of distal tip 74, will depend on the requisite flexibility and pushability at the distal end 10. Generally a longer length is more suitable for tortuous routes or providing improved crossability through narrow channels, while a shorter length is better suited for advancement through and widening of blocked vessels, providing better pushability. The length of softened distal tip 74, will depend on the requisite flexibility at the distal end 10. The length as a general guidance, may be 0 mm, 0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm or 10 mm, or a value in the range between any two of the aforementioned values, preferably between 1 and 5 mm.

The distal tip 74 is more flexible that the hollow rope tube 72 or F-region of the hollow rope tube 72 where present, which flexibility may be attributable to the thickness of the wall of the tip, its diameter and the material used to form the tip.

The maximum outer diameter (POD, FIG. 7) of the distal tip 74, may be equal to or no greater than that of the hollow rope tube 72 or the hollow rope tube 72 in the F region where present. According to one aspect of the invention, the maximum outer diameter of the distal tip 74 is 0 %, 1 %, 5%, 10%, 15%, 20% less than that of the the hollow rope tube 72 or the hollow rope tube 72 in the F region where present. According to another aspect of the invention, the maximum outer diameter of the distal tip 74 is 0.35 mm, 0.40 mm, 0.45 mm, 0.50 mm, 0.55 mm, 0.6 mm, 0.65 mm, or 0.7 mm, or a value in the range between any two of the aforementioned values, preferably between 0.4 mm and 0.7 mm.

The maximum diameter (PID, FIG. 7) of the lumen of the distal tip 74 can be smaller than, equal to or no greater than that of the hollow rope tube 72. According to one aspect of the invention it is equal to or no greater than 0.30 mm, 0.35 mm, 0.40 mm, 0.45 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm or a value in the range between any two of the aforementioned values, preferably between 0.3 mm and 0.5 mm.

The distal tip 74 may be made from a suitable biocompatible material that is conventionally used for catheter tips. The distal tip 74 is preferably formed from a material other than that used to form the hollow rope tube 72. The distal tip 74 is preferably formed essentially from a non-metallic material. The distal tip 74 is preferably formed essentially from a solid wall of polymeric material. The wall is preferably essentially a continuous cylinder, which includes a polymeric material. The distal tip 74 may be formed from a material of the group nylon, polyamide, silicone rubber, polypropylene, polyethylene, polyurethanes, poly(ethylene terephthalate) (PET), polyesters and copolymers thereof.

The proximal port 35 may be disposed with a coupling such as a Luer-lock fitting for connecting the guidewire lumen 32 to a source of pressurized fluid.

The microcatheter 100 may be provided with one or more radiopaque markers 3 for determining the position of the microcatheter 100 in a subject during placement. At least one radiopaque marker is preferably placed towards the distal end, adjacent or close to the distal port 33. One or more makers may be present on the shaft 30 and/or on the distal tip 74.

The microcatheter 100 of the present invention has a narrow profile facilitating ease of passage through narrow vasculature, and yet exhibits exceptional pushability and torque transmission from the proximal end to the distal tip. The pushing and rotational forces are transferred to the distal tip 74, which are capable of opening passages blocked by depositions or stenosed lumen. In particular, the microcatheter 100 provides guidewire support i.e. may accommodate a guidewire in its lumen 32 and facilitate the crossing of regions partially blocked by hardened calcium deposits. The ability to transmit a torque permits a rotation at the distal tip 74, that has an action capable of prising open occluded regions, and partially removing material causing the blockage. Because the microcatheter 100 has a liquid impermeable shaft and tip, suction may be applied at the proximal guidewire port 35, to remove calcified deposits or other materials. If necessary, liquid substances that assist in the dispersion of blockages can be dispensed from the distal guidewire port 33.

The guidewire may be employed in the guidewire lumen 32 of the microcatheter 100 to penetrate a blockage by iterative cycles of guidewire and microcatheter 100 advancement. In the region of the blockage, where the microcatheter 100 can no longer advance, the guidewire is extended from the distal guidewire port 33 by the application of longitudinal force at the proximal end of the guidewire by the skilled practitioner. Because the guidewire is supported in the microcatheter guidewire lumen 32, it does not buckle as the force is applied. The force applied to the blockage by the distal terminal end of the guidewire is relatively high owing to its small cross-sectional surface area; as a consequence, it is able to penetrate the blockage by a certain distance. The result is an aperture in the blockage, which can be widened by subsequent advancement of the microcatheter 100 by the same distance combined, for instance, with rotational motion. The guidewire is advanced again by a small distance, followed by the microcatheter 100 in a cycle of consecutive guidewire and microcatheter advancements, which ultimately provide a path through the blockage. The method efficiently combines the excellent pushability and torque transfer of the microcatheter 100 with the ability of the guidewire itself to apply a strong mechanical force to the blockage from its distal terminal end.

The microcatheter 100 may further be employed to exchange a guidewire in situ. Owing to its narrow profile, the microcatheter 100 can be advanced in an over-the-wire mode to the point in the vasculature where the distal end of the guidewire rests. Specifically, the proximal end of the guidewire is inserted into the distal guidewire port 33 of the microcatheter 100, and the microcatheter is advanced over the guidewire, such that the guidewire passes through the guidewire lumen 32 until it exits from the proximal guidewire port 35; during advancement time, the position of the guidewire in the vasculature is held steady so that its distal terminal end does not move. The microcatheter 100 is advanced until its distal guidewire port 33 reaches the guidewire's distal terminal end or the vicinity thereof. The in-place guidewire is withdrawn through the guidewire lumen 32 and out through the proximal guidewire port 35 of the microcatheter 100. The replacement guidewire is inserted through the proximal guidewire port 35 of the microcatheter 100 and along the guidewire lumen 32 and out through the distal guidewire port 33. Since the distal guidewire port 33 is in the same location as the original guidewire's distal terminal end or the vicinity thereof, the distal end of the replacement guidewire finds the same location in the vasculature.

The microcatheter 100 may also be applied in a retrograde approach to unblock a vascular and facilitate in guidewire placement. The retrograde approach refers to the advancement across a blocked region whereby the blocked region in one direction is harder (e.g. more calicified) that in the other direction. Where a loop in the vasculature exists that bypasses the blockage, the microcatheter 100 by virtue of its flexibility is able to loop around the blockage and approach it from the softer end, thereby loosening and breaking down the blockage.

The microcatheter 100 of the invention can be used to deliver medicament to the site of treatment. The proximal end 20 of the microcatheter 100 may be attached to a fluid delivery fitting such as a Luer connector. The fitting can be coupled to a syringe or tubing for the passage of liquid medicament, which advances along the inner lumen 32 towards the distal end 10 of the micro catheter 100. The medicament exits from the distal guidewire port 35.

Those skilled in the art will recognize that other modifications and improvements can be made to the invention without departing from the scope thereof.

Claims

1. A single lumen, balloonless catheter (100) having a proximal end (20) and a distal end (10), comprising an elongated flexible shaft (30) disposed with a longitudinal guidewire lumen (32) extending therein, which shaft (30) is connected at its distal end to a flexible distal tip (74) through which the guidewire lumen (32) extends, the flexible distal tip (74) formed from a solid-walled hollow cylinder of polymeric material, the shaft (30) comprising a hollow rope tube (72) formed from a plurality of longitudinal wire cables (40, 40') cylindrically stranded to form the hollow rope tube (72), the hollow rope tube (72) optionally having a region of transitional flexibility between the proximal (20) and distal ends (10).

2. Catheter according to claim 1 , wherein the hollow rope tube (72) has a region of transitional flexibility, and the outer diameter of the hollow rope tube (72) gradually decreases in a direction from the proximal end (20) to the distal end (10) in the region of transitional flexibility.

3. Catheter according to any of the preceding claims, wherein the hollow rope tube (72) is provided with a medium impermeable coating or outer jacket.

4. Catheter according to claim 3, wherein the hollow rope tube (72) has a region of transitional flexibility, and the thickness of the coating or outer jacket gradually decreases in a direction from the proximal end (20) to the distal end (10) in the region of transitional flexibility.

5. Catheter according to any of the preceding claims, further comprising a coupling at the terminus of the proximal end (20) for connection of the guidewire lumen (32) to a source of pressurized fluid.

6. Catheter according to any of the preceding claims, further comprising one or more radiopaque marker configured to indicate the position of the catheter in a subject.

7. Catheter according to any of the preceding claims, wherein the hollow rope tube (72) is formed by cylindrically stranding a group of metallic wire cables (40, 40') along a predetermined circle line to provide the tube (72) of the invention.

8. Catheter according to any of the preceding claims, wherein the interior surface (25) of the guidewire lumen (32) is coated with either high and/or low density polyethylene, polyamides, poly(ethylene terephthalate) (PET) or polyesters and copolymers thereof, teflon or any such material that comprises a hydrophilic and/ or reduced surface friction character

9. Catheter according to any of the preceding claims, wherein the exterior surface of the catheter (100) is coated with either high and/or low density polyethylene, polyamides, poly(ethylene terephthalate) (PET) or polyesters and copolymers thereof, teflon or any such material that comprises a hydrophilic and/ or reduced surface friction character

10. Catheter according to any of the preceding claims, wherein flexible distal tip (74) is formed essentially from nylon, polyamide, silicone rubber, polypropylene, polyethylene, polyurethanes, poly(ethylene terephthalate) (PET), or polyesters, or copolymers thereof.

1 1. Catheter according to any of the preceding claims, wherein the maximum diameter of the shaft (30) is between 0.5 mm and 0.7 mm.

12. Catheter according to any of the preceding claims, wherein the maximum diameter of the distal tip (74) is between 0.4 mm and 0.7 mm.