This is a continuation-in-part of U.S. paten application Serial No. 934,948 filed August 25, 1992. Field of the Invention

This invention relates to a dilatation catheter an more particularly to a monorail type dilation catheter having stiffening wire. Background of the Invention

Monorail dilatation catheters are commonly used i angioplasty procedures because the unique construction of suc catheters enables the rapid exchange of the catheter once it i inserted into the patient. For example, United States Patent No. 4,762,129 to Bonzel discloses a monorail catheter having a shor tube defining a guide wire lumen at the distal end of th catheter. The tube extends through the balloon from the dista end to a point proximal of the proximal end of the balloon. Thi tube terminates at an aperture opening to the exterior of th catheter such that most of the length of the guide wire from th balloon to the proximal end of the catheter is exterior of th catheter. Rapid exchange and manipulation of the dilatatio catheter is facilitated because the catheter segment contactin the surface of the guide wire is only as long as the balloon.

Although the monorail catheter provides rapid cathete exchange, it tends to lack stiffness and, therefore, is difficult to push through a patient's blood vessels. In the Bonzel construction, a stiffening wire extends through the cathete imparting stiffness to the catheter. However, the stiffenin

wire may impart stiffness in areas of the catheter wher flexibility is desired, for example in the balloon.

Due to the construction of the catheter, heretofore i has not been feasible to terminate a stiffening wire in dilatation catheter proximal of the section of the catheter i which flexibility is desired. To provide enhanced flexibility i situations where a stiffening wire is used, tapered stiffenin wires have been proposed. Schneider (Europe) AG sells dilatation balloon catheter in which a tapered stiffening wir "floats" within the catheter, i.e., the stiffening wire is no anchored at its distal and proximal ends. While thi construction, in the ideal situation, may provide the requisit stiffness and maintain distal flexibility, the floatin stiffening wire is prone to movement which can lead to problem in manipulating the catheter. Objects of the Invention

The object of the invention is to provide a dilatatio catheter in which a stiffening wire terminates proximal of th distal end of the catheter and is securely anchored in place a both its distal and proximal ends.

A more specific object of the invention is to provid a catheter of the monorail type in which a stiffening wire i anchored at the proximal end of the catheter and wherein th distal end of the stiffening wire terminates at and is secured i place within the catheter in the region of the entrance port fo the guide wire. Summary of the Invention

In accordance with the present invention, a balloo dilation catheter of the monorail type includes a stiffening wir secured at both its ends in a selected position such that maximu strength is imparted in the proximal portion of the cathete while flexibility is maintained in the distal portion of th catheter and the balloon. In the preferred embodiment, th catheter comprises an elongated tubular shaft with a dilatatio balloon mounted on its distal end. An inner tube extend

distally from a position proximal of the guide wire port and is adapted to receive the guide wire which is inserted through th port. The space between the tubular shaft and the inner tub provides an inflation lumen for the balloon. In accordance wit the invention, a stiffening wire is anchored at its proximal en within the catheter and the distal end of the stiffening wire is retained within the inner tube in the vicinity of the guide wire port.

The Drawings Fig. 1 is a schematic plan view of a monorail cathete in accordance with the invention;

Fig. 2 is a plan view partially in section showing one way in which the stiffening wire may be anchored in the lue fitting; Fig. 3 is a sectional view along the line 3-3 of Fig.

2;

Fig. 4 is a plan view partially in section showing ho the dilatation balloon is secured to the distal end of the catheter; Fig. 5 is a detailed cross-sectional view of a cathete manufactured in accordance with the preferred embodiment of the invention showing the fused laminate in the region of the guide wire port;

Fig. 6 is a sectional view along the line 6-6 of Fig. 5;

Fig. 7 is a sectional view along the line 7-7 of Fig. 5;

Fig. 8 is a detailed sectional view showing the inne tube with the retained stiffening wire inserted into the cathete shaft prior to the final assembly step in which the fuse laminate is formed;

Fig. 9 is a sectional view along the line 9-9 of Fig. 8;

Fig. 10 is a sectional view along the line 10-10 of Fig. 8; and

Fig. 11 is a plan view partially in section showing a alternative method for anchoring the proximal end of th stiffening wire within a luer fitting. Detailed Description As shown in Fig. 1, a dilation catheter in accordanc with the invention comprises an elongated tubular shaft 16 whic consists of a proximal shaft 32 and a distal shaft 34. Th distal shaft overlaps the proximal shaft in such a way as to for a guide wire port 30 through which a guide wire 12 can b introduced in conventional fashion. The lumen for the guide wir is formed by an inner tube 14 which may be made of the sam material as distal shaft 34, i.e., a flexible heat shrinkabl material such as high density polyethylene. Inner tube 1 extends from a point just proximal of the guide wire port 30 t the distal end of the balloon. The proximal end of shaft 32 i connected to a luer fitting 18. A dilatation balloon 26, whic may be of convention design, is secured at the distal end of th shaft 34. Fluid introduced through a connector 20 of luer 1 causes balloon 26 to expand in conventional fashion. In the preferred embodiment, the annular space 2 between the distal shaft 34 and inner tube 14 forms an inflatio lumen. The shaft 34 terminates proximal to the distal end of th inner tube 14 (Figure 4) . As shown in Figure 4, the proximal en of balloon 26 is connected and sealed to the distal end of th distal shaft 34. The inner tube 14 extends through the balloo 26 and is sealed at its distal end to the distal end of th balloon. Adhesive 29 provides a rounded end at the distal en of the balloon.

The balloon 26 is formed from either a noncomplian polyethylene terephthalate (PET) or a more compliant materia such as urethane. It is preferred that the balloon is coate with a highly lubricous, abrasion resistant coating. An exampl of a preferred coating is that disclosed in United States Paten No. 5,077,352 to Elton, and assigned to the assignee of th present invention, C.R. Bard of Murray Hill, New Jersey, th

disclosure of which is incorporated herein by reference. A disclosed in that patent, a flexible, lubricous organic polymeri coating is formed by applying a mixture of an isocyanate, polyol, poly(ethylene oxide) , and a carrier liquid to the surfac to be coated. The carrier liquid is removed and the mixtur reacted to form a polyurethane coating with associated pol (ethylene oxide) giving a highly lubricous, abrasion resistant, flexible coating.

A radiopaque coil spring 72 is positioned within th balloon 26 around the inner tube 14 (Figure 4) . The coil sprin 72 ensures flexibility of the balloon, the distal portion of th catheter, and the tip. The radiopaque coil spring enables th balloon 26 to be identified under X-ray. In one embodiment, th coil was formed from 0.0025 inch spring coil material such as gold-platinum combination. The formed coil may be about 4.5m long. The chosen coil parameters depend on the desire flexibility characteristics to be imparted to the distal end o the catheter.

In accordance with the invention, a stiffening wire 50, tapered at its distal end, extends from the luer 18 axiall through proximal shaft 32 to the vicinity of the guide wire por 30 where it is positioned within the inner tube 14. The tapere end of the stiffening wire 50 includes five adhesive beads 27 an is anchored within the proximal end of inner tube 14 by hea shrinking the inner tube to the stiffening wire as explaine further below. Slots 40 and 36 are cut in inner tube 14 an proximal shaft 32, respectively, so that the guide wire 12 can b inserted through the port 30 and into the lumen within inner tub 14 distal of port 30. As shown in Fig. 5, the inner tube 14 ma be bonded to a distal portion of the proximal shaft 32 and th distal shaft 34 to form a tubular laminate. Since fluid must b introduced into the balloon in the passageway 24 between th inner tube 14 and the distal shaft 34, a fluid passageway 35 i provided from the proximal shaft 32 through the thermally bonde section of the catheter into the region where the distal shaft 3

and inner tube 14 are coaxial. This region starts at the left hand side of Fig. 5 and extends into the balloon where the dista shaft 34 terminates.

Fig. 2 shows one way in which the proximal end of th stiffening wire 50 may be anchored within the luer fitting 18 The luer fitting 18 includes a cylindrical balloon leg 54, it distal end abutting against the proximal end of the proxima shaft 32. The stiffening wire 50 includes a crimp 52 at it proximal end which passes through the wall of balloon leg 54 s that the crimped portion lies against the exterior surface of th balloon leg 54. Wire 50 is positioned within the balloon le during the molding process. A strain relief tube 56 envelops th proximal shaft 32 distal of its junction with the balloon leg 54 A shrink tube 58 is placed over the crimped portion.of wire 5 and a proximal section of strain relief tube 56 and serves t secure the assembly when heat is applied. The luer may als include a conically shaped cover 60 which is secured to the lue by conventional adhesives and serves partly as a strain relie member. An alternative structure for anchoring the proximal en of the stiffening wire within the luer fitting is shown in Fig 11. In this case, the proximal end of the stiffening wire 5 includes a hook 62 which is embedded in a molded insert 64 of th luer during the molding process. The proximal end of th proximal shaft 32 is also embedded within the insert 64 durin the molding process. During the molding process, a core pin (no shown) is positioned within the mold to form a lumen 65 to enabl the introduction of air into the shaft 32 to inflate the balloon After the insert 64 is molded, the assembly is over-molded wit material 66 to form the finished luer fitting. The over-mol material 66 provides strain relief and is shaped to facilitat manipulation when a source of air is to be connected to the luer

In the preferred embodiment, the proximal shaft 32 i an extruded polymer tube (for example, high molecular weight hig density polyethylene) . However, all or part of the proxima

shaft 32 may comprise a hypotube in which case the proximal end of the stiffening wire is joined to the distal end of the hypotube rather than to the luer. If the proximal shaft were to consist of a hypotube and extruded polymer tube, the two would be joined together by conventional means.

The precise point at which the stiffening wire 50 terminates is not critical but it is preferred that the stiffening wire terminate in the vicinity of the guide wire port 30. The point of termination will depend on the desired flexibility of the distal section of the catheter.

Assembly of the preferred embodiment of the catheter according to the invention is as follows. First, the adhesive beads 27 are applied to the distal end of the stiffening wire 50 and cured. Stiffening wire 50 is then inserted into the inner tube 14 with a patency mandrel between the wire and tube in the area where the tube and wire are not to be bonded together. A shrink tube is then placed over the assembly and the inner tube 14 heat welded to the stiffening wire 50. The shrink tube and patency mandrel are removed. As shown in Figure 8, the stiffening wire assembly thus formed is then placed in the proximal shaft 32. The proximal end of wire 50 is attached to luer 18 as described above and heat welded into position.

Next, a flat mandrel 37 is positioned between inner tube 14 and proximal shaft 32 to provide for the fluid passageway 35 through the fused laminate after heat welding. Similarly, a patency mandrel (not shown) is positioned in the inner tube 14 to maintain an opening for the guide wire 12. A shrink tube is positioned over this assembly and heat applied to weld the inner tube 14 to proximal shaft 32. The shrink tube and patency mandrel are then removed.

Slots 36 and 40 are then cut through the proximal shaft 32 and inner tube 14 to provide an opening for the guide wire into the lumen within the inner tube 14. A patency mandrel is then placed within the inner tube extending through the slots.

The flared distal shaft 32 is inserted over the distal end of th proximal shaft 34 and up over the slots and patency mandrel wit the proximal end of the distal shaft 32 overlapping th stiffening wire 50. The shrink tube is applied over the join area and heat applied to weld the entire assembly to form th fused laminate. The shrink tube is removed and then the patenc mandrel and flat mandrel 37 are removed leaving the fuse laminate with a guide wire port into the inner tube 14 and th fluid passageway 35 through the fused laminate. During the welding process, the portion of proxima shaft 32 just proximal of slot 36 is "folded down" into contac with the wire retention section of inner tube 14 to form a slope wall 38 (Fig. 5) . The close positional relation among the guid wire opening 40 of the inner tube 14, the guide wire entranc port 30, and the sloped wall 38 of the proximal shaft 32 forms smooth transition and passageway for the guide wire into th inner tube 14. The smooth transition and passageway not onl aids in initial guide wire placement into the catheter, but als facilitates catheter exchange. The stiffening wire 50 may be formed from differen materials. A 302 or 304 stainless steel has been foun satisfactory. Plastics, composite metals, and other material also can be used as long as the selected material imparts th desired stiffness to the proximal portion of the catheter. With a catheter that is about 150 cm long, and with conventional length dilatation balloon, the stiffening wire 50 i about 121 cm long. In one embodiment, the wire is about 0.01 +/- 0.0003 inches diameter and tapers down to about a 0.003 +/ 0.0003 inch diameter cylindrical portion. The tapered portio may be approximately 10 +/- 0.5 cm long, and the cylindrica portion about 10 mm +/- 2mm. When the wire is formed of metallic material such as stainless steel, the distal 9 cm may b stress relieved.

The monorail catheter of the present invention offer several benefits over prior art monorail catheters. The use o

a stiffening wire anchored proximally at the luer and distall adjacent to the guide wire entrance port enhances pushability, kink resistance at the guide wire entrance port, and th flexibility transition from the proximal portion to the dista portion of the catheter. The use of a single lumen shaft at th proximal portion of the catheter maximizes th inflation/deflation lumen and reduces deflation times to minimum. The different coaxial inner and outer shaft material are chosen from materials to enhance performance characteristics. The coaxial distal section minimizes tip distension durin balloon inflation.