WO1998041277A1

WO1998041277A1 - Improved multi-lumen catheter

Info

Publication number: WO1998041277A1
Application number: PCT/US1998/005356
Authority: WO
Inventors: Steven Wiesner; Douglas Wilkins; James Segermark
Original assignee: Microvena Corporation; Infinity Extrusion & Engineering, Inc.
Priority date: 1997-03-19
Filing date: 1998-03-18
Publication date: 1998-09-24

Abstract

The present invention provides an improved multi-lumen catheter (10) which has particular utility in connection with a balloon catheter. The catheter may include a coaxial lumen proximal portion (12), and a dual lumen distal portion (14), the distal portion extending distally beyond the distal end of the proximal portion. The proximal portion may have an inner tubular member (30) having a lumen, and an outer tubular member (20). The inner tubular member is received within the outer tubular member, and may float substantially freely therewith along a majority of its length. An annular lumen (24) is defined between the inner surface of the outer tubular member, and the outer surface of the inner tubular member. The dual lumen distal portion of the catheter includes first and second lumens extending alongside one another with a septum (68) dividing the two lumens. The lumen of the inner tubular member communicates with the first lumen (70) of the distal portion, and the annular lumen of the proximal portion communicates with the second lumen (64) of the distal portion. The catheter may also include a selectively inflatable balloon (80) carried by the distal portion, with the balloon being in fluid communication with the second lumen of the distal portion. If so desired, the first lumen may be open distally and have perfusion inlet disposed proximally of the balloon, permitting blood to enter the first lumen and flow distally therethrough.

Description

IMPROVED MULTI-LUMEN CATHETER FIELD OF THE INVENTION

The present invention provides an improved catheter with multiple lumens. Such catheters can be used in creating balloon catheters for angioplasty and the like.

BACKGROUND OF THE INVENTION

Multi-lumen catheters have utility for a wide variety of medical procedures. For example, such catheters can be used to deliver a fluid through one lumen while permitting passage of a medical device through the other lumen. Similarly, hemodialysis catheters typically have one lumen for extracting the patient's blood and another for simultaneously returning processed blood to the patient's body. Most commonly, though, multi-lumen catheters are used in conjunction with balloons.

Balloon catheters have a number of applications. For example, balloons can be used to expand and deploy stents or grafts, serve as temporary anchors for other medical devices, or permit the delivery of drugs directly against vascular tissue. The details of such procedures and the method of using balloon catheters for such purposes are known to those skilled in the art and is beyond the scope of this disclosure. Angioplasty procedures are probably the most common situation in which balloon catheters are used today. Although a thorough description of angioplasty procedures is also beyond the scope of this disclosure, a basic understanding of this procedure is useful background for understanding the utility of the present invention. In most angioplasty procedures, a guiding catheter is introduced into the patient's vascular system via the femoral artery and extends upwardly into the aorta adjacent ihe ostium. A guidewire can then be passed through the guiding catheter and into the coronary arteries. By appropriately manipulating the guidewire in a known fashion, the guidewire can be passed through or positioned adjacent a vascular lesion which is to be treated. Once the guidewire is in place, a balloon catheter is urged along the guidewire and will track along the guidewire to the treatment site. A balloon catheter is typically an elongated, flexible plastic member which defines at least two passages extending along most of its length. An inflatable balloon is usually located near a distal end of the catheter. One of the elongate passages, referred to as an inflation lumen, is commonly in fluid communication with the interior of the balloon while another of the passages, referred to as a guidewire lumen, allows the guidewire to pass through the balloon catheter.

Once the balloon catheter is tracked along the guidewire (with the guidewire received within the guidewire lumen of the catheter), the balloon will be positioned within the lesion to be treated. A fluid (typically a saline solution or a contrast medium) can then be passed through the inflation lumen to inflate the balloon. The inflating balloon will exert pressure on the lesion and the walls of the artery and, hopefully, re-establish a sufficient flow of blood through the lesion. Two basic types of balloon catheters commonly in use are "dual lumen" and "coaxial lumen" balloon catheters. In dual lumen catheters, the inflation lumen and the guidewire lumen are usually positioned side-by-side with a septum dividing the two passages from one another. Coaxial lumen balloon catheters typically have two separate tubular members, with the smaller of the two tubular members being received within the interior of the other tubular member. The smaller, inner tubular member typically defines the guidewire lumen while the space between the exterior of the inner tubular member and the inner surface of the outer tubular member defines the inflation lumen of the catheter.

Dual lumen balloon catheters and coaxial lumen balloon catheters have fairly widely recognized relative advantages and disadvantages. Dual lumen catheters are frequently used because they are stiffer and have more "column strength", i.e., more resistance to buckling under a generally axial load. This enhances the ability of the physician to urge the catheter along the guidewire. In addition, fluid tends to flow through the inflation lumen of a dual lumen catheter more easily than in an annular inflation lumen of a coaxial lumen of the same cross-sectional area. Unfortunately, dual lumen catheters have disadvantages as compared to coaxial lumen catheters. As a matter of fact, the very rigidity that gives the dual lumen catheter its enhanced pushability can make it fairly difficult for the distal end of the catheter to track along the guidewire. This is particularly true where the catheter must follow the guidewire along a fairly tortuous path to reach the desired treatment site. Coaxial lumen catheters, on the other hand, tend to very easily track along the guidewire because the inner tubular member can move within the outer tubular member, permitting the two to move relatively freely with respect to one another along the curves and bends of the vasculature. This independent movement, though, makes it harder to push coaxial lumen catheters along substantial distances or along tortuous paths without buckling or kinking. Thus, both dual lumen and coaxial lumen catheter constructions have an inherent drawback in that the standard construction methods limit the ability to create an optimal catheter, which consists of a stiff proximal portion and a softer, i.e. more flexible, distal portion. Additionally, the advantage of being able to create a dual lumen catheter with three layers (i.e., both sides of the outer wall and the septum dividing the lumens) allows for creation of a smaller catheter when compared to the four layers (i.e. both sides of each of two tubes) of a coaxially constructed catheter. This allows one to maintain a larger inflation lumen for the same size catheter (making it easier to inflate and deflate the distal balloon) or to make a catheter having the same size inflation lumen. Varying the sizes and materials of these standard construction catheters can provide different benefits for the inflation and deflation of distally attached balloons.

U.S. Patent 5,370,615 (Johnson), the teachings of which are incorporated herein by reference, suggests an alternative construction which is said to combine the advantages of both the dual-lumen catheter design and a coaxial catheter design into a single balloon catheter. In Johnson's design, the proximal section of the balloon catheter has a dual lumen construction with the inflation lumen and the guidewire lumen extending alongside one another. The distal section of the catheter has a coaxial lumen construction, with an inner member being received within the outer member and the balloon. Johnson argues that this design provides maximum flexibility at the distal end while taking advantage of the pushability of dual catheter designs in the proximal section.

Johnson includes a separate transition element between the proximal and distal sections of the catheter. This complex transitional element is designed to be welded to the respective sections of the catheter and provide a passageway for communication between the guidewire and inflation lumens of the distal section and the guidewire and inflation lumens, respectively, of the proximal section. SUMMARY OF THE INVENTION

One embodiment of the present invention provides an improved multi- lumen catheter. The catheter may include a coaxial lumen proximal portion and a dual lumen distal portion, the distal portion extending distally beyond the distal end of the proximal portion. The proximal portion may have an inner tubular member having a lumen and an outer tubular member. The inner tubular member is received within the outer tubular member and may float substantially freely therewithin along a majority of its length. An annular lumen is defined between the inner surface of the outer tubular member and the outer surface of the inner tubular member. The dual lumen distal portion of this embodiment of the catheter includes first and second lumens extending alongside one another with a septum dividing the two lumens. The lumen of the inner tubular member communicates with the first lumen of the distal portion and the annular lumen of the proximal portion communicates with the second lumen of the distal portion.

In one particularly useful embodiment, the catheter of the invention is a multi-lumen balloon catheter. This embodiment also includes a coaxial lumen proximal portion and a dual lumen distal portion, the distal portion extending distally beyond the distal end of the proximal portion and carrying a balloon. The proximal portion includes an inner tubular member having a proximal guidewire lumen and an outer tubular member. The inner tubular member is received within the outer tubular member and may float substantially freely therewithin along a majority of its length. An annular proximal inflation lumen is defined between the inner surface of the outer tubular member and the outer surface of the inner tubular member. The dual lumen distal portion of this balloon catheter includes a distal guidewire lumen and a distal inflation lumen extending alongside one another with a septum dividing the two lumens.

The proximal guidewire lumen of the inner tubular member communicates with the distal guidewire lumen of the distal portion and the annular proximal inflation lumen of the proximal portion communicating with the distal inflation lumen of the distal portion. This yields essentially a single guidewire lumen and a single inflation lumen, both of which may extend along most or all of the length of the catheter. The balloon is carried by the distal portion, with the balloon in communication with the inflation lumen.

Another embodiment of the present invention provides a method for manufacturing a multi-lumen catheter. In accordance with this method, a length of a relatively flexible dual-lumen catheter segment is provided. In this dual- lumen segment, a guidewire lumen and an inflation lumen extend alongside one another with a septum dividing the two lumens. A length of a smaller tubular member and a length of a larger tubular member are also provided. The outer diameter of a distal length of the smaller tubular member is tapered from a proximal dimension which is greater than the diameter of the guidewire lumen of the dual lumen catheter section to a distal dimension which is desirably no greater than the diameter of the guidewire lumen of the dual lumen section.

In accordance with the method, a length of the distal section of the inner tubular member is inserted into a proximal length of the guidewire lumen of the dual catheter section. A length of the outer surface of the inner tubular member is then bonded to a length of the inner surface of the guidewire lumen of the dual lumen section. The outer tubular member is bonded adjacent its distal end to the dual lumen section adjacent its proximal end. This design eliminates the need for any separate transitional element yet provides a strong, generally fluid-tight seal between the proximal and distal portions of the catheter. BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic side view of a length of a multi-lumen catheter in accordance with the present invention;

Figure 2 is a schematic cross-sectional view of a balloon catheter made in accordance with an embodiment of the present invention;

Figure 3 is a schematic cross-sectional view of the catheter of Figure 2 taken along lines 3-3;

Figure 4 is a schematic cross-sectional view of the catheter of Figure 2 taken along lines 4-4; Figure 5 is a schematic cross-sectional view of the catheter of Figure 2 taken along lines 5-5;

Figure 5A is a schematic cross-sectional view of a distal portion in accordance with another embodiment of a catheter of the invention;

Figure 6 is a schematic cross-sectional isolation view of the joint between the proximal portion and the distal portion of the catheter of Figure 2; and

Figure 7 is a schematic perspective view of a distal length of an inner tubular member of a proximal portion of a catheter of the invention and a proximal length of the distal portion of the same catheter.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Figure 1 illustrates a length of one embodiment of a multi-lumen catheter

10 in accordance with the present invention. The catheter generally comprises a proximal portion 12 which has a coaxial lumen design and a distal portion 14 which has a dual lumen design.

The proximal portion 12 comprises an outer tubular member 20 and an inner tubular member 30. The inner tubular member is received within the interior of the outer tubular member along most, if not all, of its length. The inner and outer tubular members 30, 20 may be fixed with respect to one another at their respective proximal and distal ends, as discussed below in connection with Figure 2. The inner tubular member 30, however, is desirably allowed to float substantially freely within the outer tubular member 20 along most of its length. The inner tubular member 30 includes a relatively thin wall 32 which defines a first lumen 34 of the proximal portion 12. In the preferred embodiment shown, this lumen 34 is adapted to receive a guidewire 16 therein and is referred to as a guidewire lumen. The outer tubular member 20 also includes a wall 22 which defines a lumen. However, the inner tubular member is received within the interior of the outer tubular member, as noted above. A generally annular lumen 24 is defined between the outer surface of the wall 32 of the inner tubular member and the inner surface of the wall 22 of the outer tubular member. If so desired, a braid 28 or the like can be incorporated into the wall 22 of the outer tubular member to enhance the column strength and pushability of the proximal portion 12. Although the braid could, instead, be incorporated into the wall 32 of the inner tubular member 30 to improve pushability, having the braid in the outer layer also improves the hoop strength of the outer tubular member and allows greater pressures to be applied to the annular lumen 24.

The distal portion 14 of the catheter may comprise a single elongate tubular member 60. This dual lumen tubular member includes a generally annular wall 62 with a septum 68 extending from one side of this annular wall to another side of the wall. The septum will typically extend along the length of most, if not all, of the distal portion 14 to provide two distinct lumens. If so desired, a braid could also be incorporated into the wall and/or the septum of this distal portion to improve its strength. As mentioned below in connection with Figure 5A, the distal portion 14 could comprise three or more lumens, if so desired.

A first lumen 70 of the distal portion 14 is in communication with the lumen of the inner tubular member 30 of the proximal portion 12. In particular, the guidewire 16 received within the guidewire lumen 34 of the inner tubular member 30 is adapted to be passed into the first lumen 70 of the distal portion 14. Accordingly, this first lumen 70 is also called a guidewire lumen. Together, the proximal guidewire lumen 34 of the proximal portion 12 of the catheter and the distal guidewire lumen 70 of the distal portion 14 of the catheter define an elongate guidewire lumen which optimally extends from the proximal end of the catheter to the distal end of the catheter.

The second lumen 64 of the distal portion 14 of the catheter extends alongside the guidewire lumen 70, essentially parallel thereto, along most, if not all, of the length of the distal portion. The annular lumen 24 of the proximal portion 12 of the catheter is desirably in fluid communication with this second lumen 64. This would permit a fluid to be delivered from outside the patient's body to a location within the patient's body or withdrawn from the patient's body for collection or treatment. When this catheter is used in conjunction with a balloon, such as is described in connection with Figures 2-5, the fluid conduit defined by the annular lumen 24 and second lumen 64 can be used to deliver fluid to inflate the balloon. Accordingly, it is appropriate in such an application to refer to the annular lumen 24 as a proximal inflation lumen and to the second lumen 64 of the distal portion 14 as a distal inflation lumen. Hence, the proximal inflation lumen 24 of the proximal portion 12 and the distal inflation lumen 64 of the distal portion 14 define an elongate inflation lumen which optimally extends from the proximal end of the catheter to a positioned adjacent the distal end of the catheter.

The proximal portion 12 and distal portion 14 of the catheter are joined to one another to define the full catheter 10. The outer tubular member 20 is bonded adjacent its distal end 26 to the tubular member 60 of the distal portion adjacent its proximal end 66. Although these two catheters desirably overlap one another (as is shown in Figure 2), it is also possible to butt-weld the distal end 26 of the outer tubular member 20 to the proximal end 66 of the distal portion 14 using known techniques. Although this joint is not shown in Figure 1 , the distal end of the inner tubular member can be joined to the proximal end of the distal tubular member 60 using an innerlap in much the same fashion.

Figures 2-5 illustrate one particularly preferred embodiment of a multi- lumen catheter 10 of the invention. In many respects, the structure of this balloon catheter is the same as the general multi-lumen catheter structure detailed above. In particular, the proximal portion 12 generally comprises an outer tubular member 20 and an inner tubular member 30. As also shown in Figure 3, this permits a guidewire to be received through the more centrally disposed proximal guidewire lumen 34 while leaving an annular proximal inflation lumen 24 for delivery of an inflating fluid.

Much like the embodiment of Figure 1 , the distal portion 14 of the present embodiment also has a dual lumen design wherein the distal guidewire lumen 70 and distal inflation lumen 64 extend alongside one another. As best seen in Figure 5, the septum 68 serves to divide the interior of the distal tubular member 60 to define these two lumens 64, 70. In the embodiment shown, the septum is curved to yield a generally round distal guidewire lumen 70 and a generally crescent-shaped distal inflation lumen 64. It is to be understood, though, that the position and shape of this septum can be varied to yield any desired cross- sectional shape and size for each of these two lumens. Figure 5A shows another embodiment of a distal portion of the invention, wherein the distal portion 14' includes not two, but three lumens. In particular, a perfusion lumen 74 has been added to the embodiment of Figure 5. As mentioned below, it may be desirable to allow blood to flow through the distal portion of the catheter to prevent an inflated balloon to terminate flow of blood distally. Providing such a separate perfusion lumen 74 would provide a path for blood flow which would not interfere with any other aspect of the catheter. This third lumen is provided by adding a second septum 76 to separate the wire lumen 70 from the perfusion lumen 74. Any suitable number of lumens can be included in this multi-lumen distal portion 14 simply by adding additional septums. In the embodiment of Figures 2-5, the catheter includes a balloon 80 carried by the distal portion 14. This balloon can be formed in any suitable fashion. For example, the balloon can simply comprise a relatively thin, flexible sheath of material bonded at two spaced-apart locations to the exterior of the distal tubular member 60. If these bonds effectively seal the sheath, the balloon can be inflated by delivering a fluid through the inflation port 82 provided in the wall 62 of the distal portion. The second lumen 64, i.e. the inflation lumen, can be sealed at a location disposed distally of the inflation port to maintain inflation pressures. Suitable materials for the balloon are well known in the art, as are techniques for bonding the balloon to the distal tubular member and for sealing the inflation lumen.

The joint between the proximal and distal portions (12 and 14, respectively) of the catheter 10 in Figure 2 is slightly different from that shown in Figure 1 , but does so in cross section so the structure at this junction is more visible. In the embodiment shown in Figure 1 , the distal end 26 of the outer tubular member 20 simply abuts against the proximal end 66 of the distal tubular member 60. If so desired, this junction can be simply butt welded, and the joint between the inner tubular member 30 and the first lumen 70 can be similarly constructed, as noted above.

In the embodiment shown in Figures 2-6, though, a different approach is used to join the distal tubular member 60 to the inner and outer tubular members (20 and 30, respectively) of the proximal portion 12. This junction is best illustrated in Figures 4 and 6. In this embodiment, a distal length 42 of the inner tubular member 30 is adapted to fit into the proximal end of the distal tubular member 60. If so desired, the inner tubular member 20 can have substantially constant dimensions along its entire length, with the outer diameter of this tubular member being desirably no greater than the diameter of the distal guidewire lumen 70.

In a preferred embodiment, though, the inner tubular member has an outer diameter larger than the lumen of the distal guidewire lumen. For example, the diameters of the proximal and distal guidewire lumens can be essentially the same, yielding an inner tubular member with an outer diameter greater than the diameter of the distal guidewire lumen 70 due to the thickness of the wall 32. In the embodiment shown in Figures 2-6, the inner tubular member 30 includes a tapered length 40 whereby at least the outer diameter is decreased and, if necessary, the inner and outer diameter can be decreased coextensively. This yields a distal length 42 of the inner tubular member which is sized to be received in the proximal end of the distal guidewire lumen.

As schematically illustrated in Figure 7, the distal length 42 of the inner tubular member 30 can be generally aligned with the distal guidewire lumen 60. The two tubular members can then be advanced toward one another to position the distal length 42 of the inner tubular member in the distal guidewire lumen. Once the distal length 42 is so received in the proximal end of the distal guidewire lumen 70, these two elements can be bonded to one another. This bond be accomplished by heat fusing, using a suitable biocompatible adhesive or in any other suitable manner. In a preferred embodiment, these elements are joined to one another by heat fusing, using known heat fusing techniques. So long as a suitably strong bond is achieved, the precise manner in which these elements are bonded is not believed to be critical to the present invention.

In the joint illustrated in Figures 2-6, the outer tubular member 20 is expanded adjacent its distal end 26 to fit around the exterior of the proximal end 66 of the distal tubular member 60. A distal length of the outer tubular member 20 thus overlaps a proximal length of the distal tubular member 60 and this overlap can be bonded with a suitable adhesive 28 or the like, by heat fusing or using any other known joining method. Once again, so long a suitable mechanical properties are achieved, the precise manner in which the elements are joined is not critical to the invention.

If so desired, the wall 22 of the outer tubular member 20 can be tapered adjacent its distal end to better accommodate the proximal end of the distal tubular member, as illustrated. More desirably, though, the outer tubular member 20 is somewhat larger than the distal tubular member 60 so a proximal length of the distal tubular member can more readily be received in the lumen of the outer tubular member. Such a constant-diameter tubular member would be easier to manufacture and would avoid the necessity to stretch the distal end 26 to receive the proximal portion of the distal tubular member. The catheter 10 of Figure 2 includes a standard Y fitting at its proximal end. This provides a central opening 54 which helps an operator direct the guidewire 16 into the proximal guidewire lumen 34 and an angled tube 52 through which inflation fluid can be introduced to the proximal inflation lumen 24. Such fittings are well known in the art and need not be discussed in detail.

The distal portion 14 of the catheter may be made more flexible than is the proximal portion 12. In one preferred embodiment, the distal portion is formed of a plastic material which is more flexible than the materials used to form one of the inner 30 and outer 20 tubular members of the proximal portion. Much the same result can be achieved by using a plastic material in the proximal portion 12 which is the same as (or is even more flexible than) the plastic material used in the distal portion 14, but using a reinforcing tubular braid 28 or the like to stiffen one or both of the inner and outer tubular members 30, 20.

One of the particular advantages of a balloon catheter of the invention is that it will permit one to perfuse blood through the catheter when the balloon is inflated. In the embodiment of Figure 2, the distal tubular member 60 includes a perfusion inlet 72 disposed proximally of the balloon 80. Ideally, this perfusion inlet is disposed immediately proximally of the balloon, but care should be taken to ensure that the balloon does not inadvertently occlude the perfusion inlet. The perfusion inlet 72 allows a patient's blood to enter the distal guidewire lumen 70. Since this lumen 70 is open distally, this permits blood to flow distally through the guidewire lumen from a position proximal of the balloon and exit the distal end of the catheter. In this manner, one can maintain a flow of blood through the site being treated despite the fact that the balloon otherwise fills the lumen of the vessel when it is inflated. As will be understood by those familiar with perfusion balloon catheters, it may be necessary to retract the guidewire within the guidewire lumen to a position distal of the perfusion inlet to ensure sufficient blood flow through the guidewire lumen.

Alternatively, the perfusion inlet 72 could communicate with the separate perfusion lumen 74 in the alternative distal portion 14' of Figure 5A. So long as this perfusion lumen 74 is open distally, it could perform the same perfusion function without interfering with placement and use of the guidewire 16 within the wire lumen 70. The perfusion inlet 74 desirably extends distally from a position disposed proximally of the proximal end of the balloon 80. The perfusion lumen 74 optimally extends along the entire length of the balloon, but it need not so long as it defines a passage for blood to bypass the balloon.

In the design proposed by Johnson in U.S. Patent 5,370,615 and discussed above, the proximal part of the catheter has a dual lumen construction for pushability while the distal part of the catheter has a coaxial construction to enhance flexibility. Such a construction would effectively preclude one from allowing blood to pass through the guidewire lumen and bypass the balloon.

In particular, Johnson's guidewire lumen adjacent the balloon is enclosed entirely within the outer of the two coaxial catheters. This design does not allow one to introduce blood from outside the catheter to the guidewire lumen as the blood would have to pass through the inflation lumen, destroying the inflation lumen. Using a dual lumen design in the distal portion 14 of the present balloon catheter 10, the guidewire lumen extends alongside, not within, the inflation lumen. The perfusion inlet 72 can this pass through the wall 62 of the distal tubular section 60, introducing blood to the guidewire lumen 70, without compromising the integrity of the inflation lumen 64.

As noted above, the present invention also includes a method for use in connection with a multi-lumen balloon catheter. This method can be used to make multi-lumen catheters such as those illustrated in Figures 1-7, or catheters having different designs. Although reference numbers from these drawings are used in connection with the method discussed below, it should be understood that these drawings are being used solely for purposes of example and the method should not be limited to those catheter constructions shown in the drawings.

In keeping with this method, a dual lumen segment 60, a smaller tubular member 30 and a larger tubular member 20 are provided. The dual lumen segment includes a guidewire lumen 70 and an inflation lumen 64 which extend alongside one another. In a preferred construction, this is accomplished by providing a septum 68 dividing the guidewire lumen from the inflation lumen. If so desired, more than two lumens may be provided in this "dual" lumen segment. For instance, two septums (68, 76) may be provided to yield a guidewire lumen 70, an inflation lumen 64 and a perfusion lumen 74, as shown in Figure 5A.

Optimally, the smaller tubular member 30 initially has a generally uniform dimension along essentially its entire length. A distal length 42 of such a tubular member 30 can be tapered from a proximal outer dimension which is greater than the diameter of the guidewire lumen 70 of the dual lumen segment 60 to a distal outer dimension which is desirably no greater than the diameter of that guidewire lumen 70. at least the outer diameter is decreased and, if necessary, the inner and outer diameter can be decreased coextensively.

This can be accomplished, for example, by heating the distal length of the catheter to soften it and drawing it down on a mandrel to the desired dimensions. Although the dimensions of these elements are described in terms of diameters, it is to be understood that other, non-circular shapes could be used. Regardless of the shape, the distal portion 40 should be tapered to a shape having dimensions which are desirably no greater than, and optimally may be somewhat less than, the dimensions of the guidewire lumen. A length of this tapered distal portion 40 of the smaller tubular member then may be inserted into a proximal length of the guidewire lumen 70 of the dual catheter section. As schematically illustrated in Figure 7, the distal length 42 of the inner tubular member 30 can be generally aligned with the distal guidewire lumen 60. The two tubular members can then be advanced toward one another to position the distal length 42 of the inner tubular member in the distal guidewire lumen.

If the outer diameter of the distal end 42 of the distal portion is the same as the diameter of the wire lumen 70, it may be fairly difficult to insert the distal length of the distal portion in that lumen. To ease insertion, therefore, it is preferred that the distal end 42 of the smaller tubular member be somewhat smaller than the wire lumen 70.

Once the distal length 42 is so received in the proximal end of the distal guidewire lumen 70, these two elements can be bonded to one another. Optimally, a length of the outer surface of the smaller tubular member is bonded to a length of the inner surface of the guidewire lumen of the dual lumen section. This bond can be accomplished by heat fusing, using a suitable biocompatible adhesive or in any other suitable manner. In a preferred embodiment, these elements are joined to one another by heat fusing, using known heat fusing techniques. So long as a suitably strong bond is achieved, the precise manner in which these elements are bonded is not believed to be critical to the present invention.

The outer tubular member may then be bonded adjacent its distal end to the dual lumen section adjacent its proximal end. This can be accomplished using a butt weld, as illustrated in Figure 1 , using known techniques. Alternatively, the larger tubular member 20 can be expanded adjacent its distal end 26 to fit around the exterior of the proximal end 66 of the distal tubular member 60. Such a joint may, for example, have an appearance similar to that illustrated in Figures 2-6. A distal length of the outer tubular member 20 thus overlaps a proximal length of the distal tubular member 60 and this overlap can be bonded with a suitable adhesive 28 or the like, by heat fusing or using any other known joining method. Once again, so long a suitable mechanical properties are achieved, the precise manner in which the elements are joined is not critical to the invention.

If so desired, the wall 22 of the outer tubular member 20 can be tapered adjacent its distal end to better accommodate the proximal end of the distal tubular member, as illustrated. More desirably, though, the outer tubular member 20 is somewhat larger than the distal tubular member 60. As explained above, such a constant-diameter tubular member would be easier to manufacture and would avoid the necessity to stretch the distal end 26 to receive the proximal portion of the distal tubular member. EXAMPLE

The materials used in forming the various components of the catheter 10 of the invention, as well as their individual and relative dimensions, will depend to a great deal on the intended use of the catheter. In some circumstances, a catheter may be needed to treat a stenosis in a fairly large, easy to reach vessel. In such circumstances, the catheter and its balloon can be fairly large and formed of relatively rigid materials. In contrast, catheters used to traverse tortuous vasculature to reach more selective sites will typically require narrower tubular members formed of more flexible materials. Accordingly, it is difficult to generalize the materials and dimensions for catheters of the invention as these parameters will be varied on a case-by-case basis.

By way of example, one catheter believed to be appropriate for a variety of applications utilizes an inner tubular member having an inner diameter of about 0.018 inch (about 0.46 mm) and an outer diameter of about 0.024 inch (about 0.61 mm)is used. This tubular member 30 can be formed of, for example, high density polyethylene. The outer tubular member 20 can comprise a hypotube formed of a metal, e.g. shape memory alloys like Nitinol, or can be a more conventional plastic tube made from, for example, a high density polyethylene. This outer tubular member can have an inner diameter of about 0.038 inch (about 0.97 mm) and an outer diameter of about 3.5 French (about 0.047 inch or about 1.2 mm). As noted above, one or even both of these inner and outer tubular members can include a braid, such as a stainless steel braid, incorporated in the wall to help stiffen the wall and improve its resistance to rupture or tearing.

The distal tubular member 60 of this example can have an outer diameter of about 0.037 inch (about 0.94 mm), a round distal guidewire lumen having a diameter of about 0.018 inch (about 0.46 mm) and a generally crescent-shaped distal inflation lumen having a maximum radial height of about 0.010 inch (about 0.25 mm). This distal tubular member is optimally formed from a material which is softer than the material used to form either of the proximal tubular members. For example, suitable materials could include a moderate grade (e.g. 50D) of Pebax or nylon, or a blend of about 25-60% low density polyethylene with a balance of high density polyethylene.

In this configuration, the inner tubular member has an inner diameter about the same size as the diameter of the distal guidewire lumen 70. In this circumstance, these two members can be butt welded so that the lumens align with one another to produce the combined guidewire lumen. Alternatively, a tapered length 40 of about 3 mm can be used to take the outer diameter of the distal end of the inner tubular member 30 down to about 0.017 inches, preferably also thinning the wall 32 along this length, too, to maximize the size of the guidewire lumen at this joint. Once the inner tubular member and distal tubular member are placed in the appropriate physical relationship, they can be bonded to one another as previously described. The proximal end 66 of the distal tubular member 60 can than be inserted into the distal end 26 of the larger outer tubular member 20 and bonded thereto as described above. The balloon can be made of any of a wide range of materials, depending on the specific properties needed in the application for which the catheter is to be used. For example, the balloon can be made of polyethylene, nylon or a suitable urethane. The balloon will typically be between about 4 cm and about 6 cm long (measured in terms of its dilating surface) and have an inflated diameter of anywhere from about 1.5 mm for applications in smaller vessels to about 30 cm for much larger vessels.

While a preferred embodiment of the present invention has been described, it should be understood that various changes, adaptations and modifications may be made therein without departing from the spirit of the invention and the scope of the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A multi-lumen catheter comprising a proximal portion and a distal portion, the distal portion extending distally beyond the distal end of the proximal portion; the proximal portion comprising an inner tubular member having a lumen and an outer tubular member, the inner tubular member being received within the outer tubular member and floating substantially freely therewithin along a majority of its length, an annular lumen being defined between an inner surface of the outer tubular member and an outer surface of the inner tubular member; the distal portion including first and second lumens extending alongside one another with at least one septum dividing the two lumens; the lumen of the inner tubular member communicating with the first lumen of the distal portion and the annular lumen of the proximal portion communicating with the second lumen of the distal portion.

2. The multi-lumen catheter of claim 1 wherein the distal portion is formed of a plastic material which is more flexible than the material used to form one of the inner and outer tubular members of the proximal portion.

3. The multi-lumen catheter of claim 1 wherein one of the inner and outer tubular members of the proximal portion comprises a plastic material reinforced with a tubular braid.

4. The multi-lumen catheter of claim 3 wherein the inner tubular member is braided.

5. The multi-lumen catheter of claim 3 wherein the outer tubular member is braided.

6. The multi-lumen catheter of claim 3 wherein the distal portion is more flexible than the proximal portion.

7. The multi-lumen catheter of claim 1 further comprising a selectively inflatable balloon carried by the distal portion of the catheter.

8. The multi-lumen catheter of claim 7 wherein the balloon comprises a flexible plastic material carried about the exterior of the distal portion adjacent a distal end thereof, the balloon being in fluid communication with the second lumen of the distal portion.

9. The multi-lumen catheter of claim 8 wherein the first lumen has a perfusion inlet disposed proximally of the balloon, the perfusion inlet permitting blood to enter the first lumen.

10. The multi-lumen catheter of claim 9 wherein the first lumen is open distally and permits blood to flow distally through the first lumen.

11. The multi-lumen catheter of claim 8 wherein the second lumen is sealed at a location disposed distally of the balloon.

12. The multi-lumen catheter of claim 1 wherein the distal portion further comprises a third lumen extending alongside at least one of the first and second lumens, with a second septum dividing the third lumen from at least one of the first and second lumens.

13. The multi-lumen catheter of claim 12 wherein the third lumen extends alongside the second lumen and defines a perfusion lumen through which blood may flow.

14. The multi-lumen catheter of claim 13 further comprising a selectively inflatable balloon carried by the distal portion of the catheter.

15. The multi-lumen catheter of claim 14 wherein the perfusion lumen is distally open and extends distally from a point proximal to a proximal end of the balloon, further comprising a perfusion inlet extending through a wall of the distal portion at a location disposed proximally of proximal end of the balloon and allowing blood to flow into the perfusion lumen.

16. A multi-lumen balloon catheter comprising a proximal portion and a distal portion, the distal portion extending distally beyond the distal end of the proximal portion and carrying a balloon; the proximal portion comprising an inner tubular member having a proximal guidewire lumen and an outer tubular member, the inner tubular member being received within the outer tubular member and floating substantially freely therewithin along a majority of its length, an annular proximal inflation lumen being defined between an inner surface of the outer tubular member and an outer surface of the inner tubular member; the distal portion including a distal guidewire lumen and a distal inflation lumen extending alongside one another with a septum dividing the two lumens; the proximal guidewire lumen of the inner tubular member communicating with the distal guidewire lumen of the distal portion and the annular proximal inflation lumen of the proximal portion communicating with the distal inflation lumen of the distal portion.

17. The multi-lumen balloon catheter of claim 16 wherein the distal portion is formed of a plastic matehal which is more flexible than the material used to form one of the inner and outer tubular members of the proximal portion.

18. The multi-lumen balloon catheter of claim 16 wherein one of the inner and outer tubular members of the proximal portion comprises a plastic material reinforced with a tubular braid.

19. The multi-lumen balloon catheter of claim 16 wherein the balloon comprises a flexible plastic material carried about the exterior of the distal portion adjacent a distal end thereof, the balloon being in fluid communication with the distal inflation lumen.

20. The multi-lumen catheter of claim 19 wherein the distal inflation lumen has a perfusion inlet disposed proximally of the balloon, the perfusion inlet permitting blood to enter the distal guidewire lumen.

21. The multi-lumen catheter of claim 16 wherein the distal guidewire lumen is open distally and permits blood to flow distally through the distal guidewire lumen.

22. A method for use in connection with a multi-lumen balloon catheter, comprising: a. providing dual lumen segment comprising a guidewire lumen and an inflation lumen extend alongside one another, a length of a smaller tubular member and a length of a larger tubular member; b. tapering the outer diameter of a distal portion of the smaller tubular member from a proximal dimension which is greater than the diameter of the guidewire lumen of the dual lumen segment to a distal dimension which is desirably no greater than the diameter of the guidewire lumen of the dual lumen segment; c. inserting a length of the distal portion of the smaller tubular member into a proximal length of the guidewire lumen of the dual catheter section; d. bonding a length of the outer surface of the smaller tubular member to a length of the inner surface of the guidewire lumen of the dual lumen section; and e. bonding the larger tubular member adjacent its distal end to the dual lumen section adjacent its proximal end.