CA2035914A1 - Co-axial balloon catheter - Google Patents

Abstract

ABSTRACT

A catheter is provided having an elongate body including an inner tubular element and an outer tubular element. The inner element is contained within and located by the outer element to define a first lumen and a second lumen is defined at least in part by the outer element. First and second coupling tubes are connected by a junction to a proximal end of the body with each of the coupling tubes connected individually to one of the respective first and second lumens. A method of manufacture is also disclosed.

Description

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This invention relates to dual lumen catheters which have particular application in the treatment of stenosed blood vessels. The invention also relates to a method of manufacturing the catheter.
Dual lumen catheters are used in a variety of medical procedures such as haemodialysis and angioplasty. It has become common to use a single catheter which is built from an extrusion to include two distinct lumens. The requirements of such a catheter demand small cross-sections, selected flexibilities and usefulness with techniques such as the Seldinger insertion technique. Also, not all procedures call for the same characteristics but it is common to require a small diameter and clear well formed lumens in flexible bodies which may also require very soft tips to minimize the risk of damage to body tissue, particularly during prolonged access. These perameters are considered in the following description which uses angioplasty as an exemplary procedure in describing a preferred embodiment of catheter, and the manufacture of a catheter suitable for such use.
Angioplasty catheters have been successfully used for a number of years in the treatment of blood vessels obstructed or stenosed with plaque. An angioplasty catheter includes, near its distal end, a balloon which can be inflated by means of pressurized fluid supplied through one of two lumens defined by an extrusion forming the body of the catheter. The treatment involves the location of the balloon in the stenosed section of - ' the blood vessel, followed by inflation and deflation through this lumen. During inflation, the balloon compresses the plaque and stretches the blood vessel such that the cross-sectional area of the stenosis is increased until it is comparable to that of the unobsteucted blood vessel. When the treatment has been completed the balloon is deflated and the catheter removed. The treated blood vessel maintains substantially its enlarged cross-section to permit the free flow of blood through this pGrtion.
The second lumen is used to insert the catheter over a Seldinger wire and can be used with the catheter in place to monitor blood flow pressure at the site or to administer -~' midicament.
To perform satisfactorily a suitable angioplasty catheter must also possess a number of physical properties. For ease of insertion it is preferable that the catheter is flexible, has a relatively small cross-sectional area, and has a smooth outer surface. Also, insertion using the Seldinger technique requires a tapered distal end just beyond a balloon which must be strong enough to withstand the application of high pressures without rupture and which must always inflate to a predetermined shape and size.
Examples of typical structures intended for this purpose are found in U.S. Patent Nos. 4,338,942 to Fogarty, 4,646,719 to Neuman et al. and 4,402,307 to Hanson et al.
All of the prior art structures suffer from disadvantages and among them are the fact that the structures require a relatively large cross-sectional area for the body, 3~J~
and there is no provision to permit the tip to be made simply from a very flexible material. These problems stem from the fact that the currently used methods of manufacture depend on starting with an extrusion and this of course does not lend itself to the provision of a tip having more flexibility than the main body. Also, the inherent requirements of extruding mean that the outside diameter of the body of the catheter has a size dictated by the need to provide two distinct lumens separated by a wall which can withstand pressures used to inflate the balloon. In some instances attempts were made to overcome these disadvantages by using coaxial tubes of different materials with the inner tube projecting to form the tip. This is not a solution because the tubes tend to move longitudinally relative to one another, particularly during insertion. This makes it difficult to insert the structure over a Seldinger wire, the preferred method of insertion.
It is an object of the present invention to provide an improved catheter which overcomes some of the disadvantages of the prior art and which has particular utility in angioplasty procedures.
In accordance with one of the aspects of the invention, a catheter is provided having an elongate body including an inner tubular element and an outer tubular element. The inner element is contained within and located by the outer element to define a first lumen and a second lumen is defined at least in part by the outer element. First and second coupling tubes are connected by a junction to a proximal end of the body with each of the coupling tubes connected individually to one of the r~i ~
respective first and second lumens.
In a second of its aspects, the invention provides a catheter having an elongate body including an inner tubular element and an outer tubular element. The inner element is contained within the outer element to define a first lumen and the outer element defining a second lumen. First and second coupling tubes are connected by a junction to a proximal end of the body with each of the coupling tubes connected individually to one of the respective first and second lumens.
In other aspects of the invention, a method is provided for manufacturing the catheters.
These and other aspects of the invention will be better understood with reference to the drawings, in which:
Fig. 1 is a perspective view of an angioplasty catheter in accordance with a preferred embodiment of the present invention and having a balloon in a deflated condition;
Fig. 2 is an enlarged sectional view of line 2-2 of Fig. l;
Fig. 3 is a side view, drawn to a larger scale than Fig. 1, and illustrating the balloon after inflation; and Fig. 4 is view similar to Fig. 2 and illustrating an alternative embodiment of the catheter.
The preferred embodiment of the angioplasty catheter according to the present invention will now be described in detail, firstly with reference to Fig. 1 of the drawings. mis view shows in perspective an angioplasty catheter, designated generally by the numeral 20, and including a flexible main body 22 having a distal end 24 defining a tapered tip 25 to ~ 3 facilitate insertion into a vein of a patient, and a proximal end 26 for connection, by means of a junction 28, to the respective distal ends of a guide wire tube 30 and a fluid supply tube 32. The tube 30 is larger than tube 32 although for quick response the tube 32 should be as large as possible so that inflation pressure will cause rapid flow to the balloon for inflation. The tubes 30, 32 are in communication with respective circular guide wire and fluid supply lumens 34, 36 defined within the main body 22 (Fig. 3) and are provided with conventional connectors 35, 37 at the respective proximal ends of the tubes.
The body 22 extends from the junction 28 to the tip 25 and passes through a balloon 40, (shown in a collapsed condition). A tubular shipping protector (not shown) for location over the distal end 24 and balloon 40 would normally be provided to protect the balloon and to retain it in a collapsed condition ready for insertion.
The elongate main body 22 meets, at its proximal end 26, the junction 28 and is supported by a short sleeve 42 as has become conventional in this kind of structure. Part of the sleeve is molded into the junction 28 and projects from the junction to provide strength where the flexible tube meets the rigid junction. Immediately beyond the sleeve 42, there is a tapered zone 44 where the original body diameter has been reduced to a new diameter as will be described with reference to the method of manufacture. Sufficient to say at this point that the final diameter of the body 22 is the result of a procedure which reduces the diameter of the extrusion used to make the ' : ' .
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body thereby not only providing a smaller diameter, but also improved molecular orientation for strength and an improved surface finish.
In order to better understand the shaping of the body, reference is next made to Fig. 2. It will oe seen that the body 22 includes an inner element 46 and an outer element 48. The innner element is embedded in the outer element so that the inner element is both located and restrained by the outer element. A portion of the inner element borders the lumen 36, and the other lumen 34 is formed inside the tubular inner element 46.
The resulting cross section shown in Fig. 2 is obtained by starting with a tubular inner element placed inside a tubular outer element along with two mandrels. The first mandrel has the shape of the lumen 34 and the other mandrel fits the shape shown for the lumen 36. Both mandrels are of nylon and are disposed of after the manufacturing process.
The elements 46, 48 are made from a soft synthetic plastics material sold under the trade mark PEBAX, the outer element being PEBAX 7033 and the inner element PEBAX 6333.
These are two different Durometers with the inner element being softer than the outer element.
The reduction in diameter is achieved by placing the assembled inner and outer elements with the mandrels in a die which is heated and the assembly is drawn through the die to deform the elements into the shape shown in Fig. 2. Sufficient heat is provided to soften these elements and the speed at which the assembly is drawn is dictated by the need to provide .

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sufficient heat and residence time to achieve the changes in shape and the flow of the material into the shape shown in Fig.

2. This is continued to complete the body prior to assembly in the remainder of the structure shown in Fig. 1.
After the drawing has been completed, the nylong mandrels are removed by first pulling the ends to stretch the mandrels thereby reducing the cross sections to make it possibly to withdraw them. The stretched mandrels are then discarded.
With the body formed, the sleeve 42, and junction 28 are manufactured and assembled with the tubes 30, 32. The larger tube 30 is associated with lumen 34 and the smaller tube with the lumen 36.
A portion of the outer element 48 is cut away from the assembly leaving the inner element exposed to form the distal end 24 as will now be described with reference to Fig. 3.
As seen in Fig. 3, the body 22 enters the balloon 40 which is shown in this view in an inflated condition, and at the other end, the balloon is attached to the inner element 46 which extends beyond the outer element 48 leaving the lumen 36 (Fig.
2) exposed at its end inside the balloon for inflation and deflation of the balloon.
A conventional radiopaque band 50 is positioned about the element 46 centrally of the balloon before the balloon is attached by bonding to the body 22 at the ends of the balloon.
The tip 25 includes a tapered end portion 52 to improve insertion over the Seldinger wire which projects through the inner element 46 and out of the end of the tip by following the circular lumen 34 (Fig. 2).

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It will be clear from the description ofJt~ ~ f~ ~ ed embodiment that the inner element 46 can have a selected stiffness suitable for creating the tip 25 and be supported by the outer element 48 which can be of the same material or, as is preferably done, a stiffer material having a different Durometer from that of the inner element 46.
The arrangement of the preferred embodiment is such that the maximum use of material is made with a minimum outside diameter. The resulting structure has a diameter of 3 French and because of the selection of the cross section, there is significant strength in the structure. In particular, a portion of the inner element 46 forming a septum 54 (Fig. 2) between the lumens 34 and 36 is curved to resist pressures in the lumen 36 when the balloon is inflated. This ensures integrity of the lumen 36 and of the lumen 34 when the balloon is in the inflated condition. Clearly when the septum must be chosen to have sufficient strength if this integrity is important and the proportions of the structure are to some extent controlled by the requirement to apply high pressures in the lumen 36.
An alternative embodiment is illustrated by way of cross section in Fig. 4. This arrangement differs from that shown in Fig. 2 in that an inner element 56 is totally contained within an outer element 58 which originally was formed with a septum 60 before being drawn down to the shape shown. Typically the outer element 58 will have a double-D cross section, and the lumens being large enough that the inner element 56 can be pushed down one of the lumens with some minor deformation of the septum 60. Subsequent drawing causes flow of the material into ~ J~ ~ L ~

the shape shown. It will be appreciated that this structure locks the inner element 56 more positlvely to the outer element 58 and there is no possibility that pressure build up in a lumen 62 feeding the balloon will force separation of the inner and outer elements. This is a possibility in the preferred embodiment although it is not likely and if it does happen, it will have not effect on the procedure since the elements are arranged such that the lumen 34 is self contained and will not be affected by any pressure leakage between the inner and outer elements from the lumen 36. Nevertheless, in some circumstances it may be preferred to create the structure shown in Fig. 4 provided that a slightly larger diameter is acceptable because this tends to be about one half French larger than the preferred embodiment for similar usage.
In general, the body of the catheters according to the invention is typified by being of two elements, one inside the other, and two lumens, the lumens being separated by a septum formed from at least a portion of the inner element as shown in Fig. 2, and possibly also by a portion of the outer element as shown in Fig. 4. These and other embodiments and methods are within the scope of the invention as claimed.

Claims (22)

1. A catheter comprising:
an elongate body having proximal and distal ends, a tubular inner element, and a tubular outer element, the inner element being contained within and retained by the outer element and forming a first lumen, the elements combining to define a second lumen;
first and second coupling tubes;
juntion means coupled to a proximal end of the body and to the coupling tubes and connecting the tubes individually each to one of the respective first and second lumens; and a tip at the distal end of the body.

2. A catheter comprising:
an elongate body having proximal and distal ends, a tubular inner element, and a tubular outer element, the inner element being contained within and retained by the outer element and defining a first lumen and the outer element defining with a portion of the inner element a second lumen;
first and second coupling tubes:
junction means coupled to a proximal end of the body and to the coupling tubes and connecting the tubes individually each to one of the respective first and second lumens; and a tip at the distal end of the body.

3. A catheter comprising:
an elongate body having proximal and distal ends, a tubular inner element and a tubular outer element, the inner element being contained within and retained by the outer element to define a first lumen and the outer element defining a second lumen;
first and second coupling tubes;
junction means coupled to a proximal end of the body and to the coupling tubes and connecting the tubes individually each to one of the respective first and second lumens; and a tip at the distal end of the body.

4. A catheter comprising:
an elongate body having proximal and distal ends and inner and outer elements, the inner element being coupled to the outer element and the elements combining to define a septum between first and second lumens;
junction means coupled to the proximal end to provide external fluid connections to the respective first and second lumens; and an end structure at the distal end of the body.

5. A catheter as claimed in claim 4 in which the end structure includes a balloon, and in which the distal end of the first lumen ends inside the balloon and the distal end of the second lumen projects beyond the balloon and has a tip.

6. A catheter as claimed in claims 1, 2, 3 or 4 in which the inner element projects beyond the outer element.

7. A catheter as claimed in claims 1, 2, 3 or 4 in which the inner element is more flexible than the outer element and projects at said distal end beyond the outer element.

8. A catheter as claimed in claim 5 in which the tip is of a material which is softer than that of the outer element.

9. A catheter as claimed in claims 1, 2, 3, or 4 in which the body includes a tapered zone adjacent the junction means.

10. A catheter as claimed in claim 4 in which the septum is part of the inner element.

11. A catheter as claimed in claim 4 in which the septum includes parts of the inner and outer elements.

12. A angioplasty catheter comprising:
an elongate main body having proximal and distal ends and made up of a tubular inner element and a tubular outer element, the inner element being located and restrained in place by the outer element, the distal end having a tip formed from the inner element and the outer element terminating at an end spaced from the tip, the inner and outer elements combining to define a septum between first and second lumens;
a balloon extending outside the body and containing a portion of the body, the balloon being sealed at one of the ends of the balloon to the outer element and at the outer end to the inner element adjacent the tip so that the distal end of the first lumen ends inside the balloon for use in inflating and deflating the balloon and the tip is outside the balloon so that the second lumen can be used for Seldinger insertion; and junction means coupled to the body at the proximal end to provide fluid connection to the respective first and second lumens and to provide access to the second lumen for Seldinger insertion.

13. A catheter as claimed in claims 1, 2, 3, 4 or 12, in which the body is circular in cross-section.

14. A catheter as claimed in claims 1, 2, 3, 4, or 12, in which the inner element is circular in cross-section.

15. A catheter as claimed in claims 1, 2, 3, 4, or 12, in which the inner element and outer element are circular in cross-section.

16. A catheter having an elongate body with proximal and distal ends, and defining two lumens separated by a septum, tip structure at the distal end, and junction means at the proximal end for coupling to the lumens individually, the improvement in which the body includes inner and outer elements, the inner element being located and restrained by the outer element and the elements combining to define the septum.

17. Structure as claimed in claim 16 in which the septum is part of the inner element.

18. Structure as claimed in claim 16 in which the septum parts of the inner and outer elements.

19. A method of manufacturing a catheter comprising the steps providing thermoplastic inner and outer element, the inner element being proportioned to fit inside the outer element leaving space inside the outer element;
engaging shaped mandrels, a first inside the inner element and a second in said space, the mandrels having constant cross-sectional corresponding to the desired cross-sectional shapes of respective first and second lumens to be formed in the body;
applying heat and tension to the body locally in a die having the desired outside shape of the body, and moving the body progressively through the die thereby causing the materials of the elements to flow so that the inner element becomes embedded in the outer element and said lumens are shaped about the respective mandrels;
withdrawing to mandrels;
attaching junction means to a proximal end of the body and manufacturing an end structure on the distal end of the body.

20. A method as claimed in claim 19 in which the step of manufacturing an end structure comprises:

removing a portion of the outer element adjacent said distal end to expose a portion of the inner element;
placing an elongate balloon over said exposed portion and attaching the balloon to the outer element at one end of the balloon and to said portion of the inner element to contain a distal end of the outer element inside the balloon for inflating and deflating the balloon.

21. A method as claimed in claims 19 or 20 in which the outer element before heat is applied, is tubular and in which said space is between the inner and outer elements.

22. A method as claimed in claims 19 or 20, in which the outer element, before heat is applied includes a septum dividing the element to define two D-shaped lumens, and in which the inner element is inserted into one of the lumens and said space is defined by the other of the lumens.