WO1989008471A1

WO1989008471A1 - Low-profile angioplasty balloon catheter with guidewire

Info

Publication number: WO1989008471A1
Application number: PCT/US1989/000725
Authority: WO
Inventors: Bandula Wijay; Paolo Angelini
Original assignee: Leocor, Inc.
Priority date: 1988-03-07
Filing date: 1989-02-28
Publication date: 1989-09-21
Also published as: ES2012685A6; JPH03503244A; KR900700152A; US4884573A; AU4189489A; EP0406269A1

Abstract

A very low-profile balloon catheter (12) is disclosed that allows for an independently movable, steerable and removable guidewire (26). After removal of the guidewire, the balloon catheter retains adequately angiographic and hemodynamic characteristics. Such catheter construction allows for exchange of guidewires. A tracking mechanical device is included and provides excellent and easy advancement of the balloon catheter through severe obstructions.

Description

Low-profile angioplasty balloon catheter with guidewire.

Background of the Invention

Field of the Invention

This invention pertains to balloon catheter angio¬ plasty, and more specifically to dilation of an obstructed vessel in the human anatomy by a balloon catheter of novel design for use in the treatment of arterial occlusive disease.

Description of the Prior ftrt At the present time, the technique to perform an¬ gioplasty has employed a basic pattern. Once it has been determined that angioplasty is to be employed to treat an aterial occlusion, a guiding catheter is used to lead a balloon catheter to the aortic origin of the vessel to be dilated, while also allowing monitoring of aortic pres¬ sure. In addition, the guiding catheter permits dye in¬ jections to clarify the vascular anatomy during the proce¬ dure in a manner similar to that employed when a smaller diagnostic vascular catheter is employed for diagnostic angioplasty. Once the lesion is reached, the guiding catheter supports the balloon catheter as it crosses the lesion addressed.

The balloon catheter system comprises the balloon catheter and a guidewire. The essential function of the balloon catheter system is to carry safely an inflatable balloon across a vascular obstruction. The guidewire used in the system must be visible on fluoroscopy, it must be delicate, and the proximal end thereof must be responsive when manipulated from outside. Historically, these re- quirements have led to the development of the so-called "removable, steerable" guidewire concept. Typically, a 0.014" to 0.018" guidewire is passed through the balloon catheter and manipulated independently. This system, therefore, allows for the removal of the guidewire while leaving the balloon catheter in the vascular position attained, and permits the use of different guidewires having various qualities and tip shapes.

Prior art balloon catheters have these two essen¬ tial features: (1) they are capable of carrying the bal¬ loon to the desired position through the occluded vascular segment, and (2) they allow the inflation and deflation of the balloon from an external port. Most of the balloon catheters have a double passageway or lumen: (1) a first one dedicated to inflate and deflate the balloon with a hydraulic system, and (2) a second one for passing the guidewire therethrough while being large enough to main- tain a channel around it to permit monitoring of the tip pressure (i.e., the inside pressure of the vascular sys¬ tem) or alternately, to permit monitoring of the vascular anatomy by radiographic dye injection.

It has become apparent during the last few years of clinical experience that attaining the lowest profile of the balloon catheter system is quite desirable in order to facilitate the passage of the balloon across severe and remote vascular obstructions. This technological chal¬ lenge has led to two simplifications of the above- described balloon catheter system. A first simplification referred to as the "Hartzler's design" sacrifices one lumen of the balloon catheter. This leads to the need for a non-removable and/or non-independently steerable guide- wire (i.e., the whole system of wire and balloon catheter steers). In such a design, the capacities for monitoring pressure and for dye injuection to determine vascular anatomy are consequently lost. In a second simplifica¬ tion, the guidewire is made hollow and carries an inflat¬ able balloon on its tip. This structure is sometimes referred to as the "balloon-on-the-wire" system. In this system, the capacities of monitoring distal pressure and anatomy by dye injection are also lost, while the steera- bility remains impaired as it is necessary to steer the balloon with the system. It must be noted here that guidewires that are not attached to a balloon catheter distally can be advanced and/or rotated with precision. By contrast, when the balloon catheter is attached dis¬ tally to the guidewire, the bulkiness of the balloon im¬ pairs the precise advancement or rotation of the guide- wire, while the balloon itself may become twisted by steering the system. The structure disclosed herein achieves a low pro¬ file in the balloon catheter system by reducing catheter wall thickness while maintaining at least most of the favorable qualities of the traditional so-called "steer¬ able, removable guidewire system". In double-lumen bal- loon catheters, as described above, typically four walls are present in a cross-sectional diameter. Each of these walls, when made of such conventional materials as poly¬ ethylene, polyurethane and polyvinyl chloride, has a thickness of at least 0.005". This fact leads to having at least 0.020" in the cross-sectional diameter of such traditional double-lumen catheters dedicated to material only. This material cross-sectional space constitutes a sizable portion of the entire cross-sectional thickness, which typically is 4.3 French or 0.0056". A minimum of 0.005" wall thickness is required when these materials are used in order to withstand inflation pressures and to prevent collapsing of the catheter body walls when vacuum is created to deflate the balloon.

A different and newer material is employed in the inventive structure herein set forth to build a double- lumen catheter. The material is polyimid plastic, which has a tensile strength 3-5 times greater than conventional materials. Use of such materials results in significant economies in the cross-sectional diameter dimension of the balloon catheter. Only a total of 0.004" of cross-sec¬ tional diameter of an otherwise typical double-lumen bal¬ loon catheter is occupied by the catheter walls. Having realized a significant saving in material thickness, the new balloon catheter, described hereinafter not only will have a low profile at the level of the balloon, which therefore becomes the critical profile in terms of capac- ity of crossing severe vascular obstructions, but also will enable the usage of traditional diagnostic catheters to guide the balloon catheter system. This is an advan¬ tage as traditional diagnostic catheters have excellent torque control and distal tip flexibility and curve memory compared with guiding catheters commonly used in angio¬ plasty. In addition, diagnostic catheters seat better than the guiding catheters commonly used in the ascending aorta, and the use of a diagnostic catheter to guide the balloon catheter results in less of a chance for the bal- loon catheter to dislodge from the coronary orifice when the balloon catheter is advanced in the coronary arteries.

It must be recalled at this point that balloon catheter angioplasty is currently being done by using a guiding catheter, which is different from the catheters used for diagnostic angioplasty. Such guiding catheter has a non-thrombogentic and Teflon-lined, low-friction inner lumen of relatively large inner diameter (typically, 0.070-0.072") which does not taper at the tip, thereby having poor distal tip flexibility, and which results in a less adequate torque control and curve memory than achieved by diagnostic catheters.

As set forth more fully hereinafter, the embodi¬ ments of polyimid plastic catheters, being lower in cross- section, allow the usage of the same catheters used for diagnostic angioplasty (e.g., having a dimension of 6 or 7 French) as a guiding catheter, thereby resulting in an economy of materials, time expenditure, and a reduction in patient risk during angioplasty.

Additionally, the new balloon catheter system de- scribed herein allows for an improved progressive maneuver for advancing the balloon catheter over the guidewire. The presently used systems frequently find difficulty in forcing the balloon tissue through the occlusive lesion, even after passing the guidewire. Most commonly, this passage is accomplished by simultaneously locking the guiding catheter into the arterial ostium or origin of the addressed vessel and pushing the balloon catheter slowly, while gradually retrieving the guidewire which previously had already passed through the lesion.

In one embodiment of the present structure, a new mechanical device is disclosed that allows for a gradual, forced protrusion of the balloon tip over the guidewire. This device is sometimes referred to herein as a "mechan¬ ical slider". Such a mechanical slider device allows for enhanced pushing forces to be safely and gradually used by a single operator physician. Hence, using such a device in combination with the catheter structure disclosed here¬ in provides a maneuver that is both important from a safety point of view, as well as providing economies in physician time usage.

Summary of the Invention

The invention disclosed herein includes a balloon catheter system with the capacity for an independently movable guidewire, while including a preferred embodiment consisting of a "mechanical slider". The guiding catheter used with this balloon catheter system can either be a conventional guiding catheter or a diagnostic angiographic catheter with a larger than 0.040" inner lumen.

The preferred embodiment of the balloon catheter includes a double lumen, coaxial catheter body made from tubes of polyimid plastic having wall thickness of about 0.002". In the preferred embodiment, the distal segments of the coaxial catheter body are made from a softer mater¬ ial than polyimid, such as nylon, polyethylene or polyure- thane, or related materials having a similar stiffness. The proximal portion of the catheter is made from polyimid plastic, a material having a tensile strength of 20,000 psi, which lends stiffness to the catheter body so that it is pushable. The softer distal end, made of .nylon or a: similar material, provides tip softness to improve tracta- bility through tortuous arteries. The inner lumen is dedicated primarily to the passage of a guidewire and is _ referred to sometimes herein as the "guidewire lumen". The outer lumen is dedicated to the inflation and defla¬ tion of the balloon and is referred to sometimes herein as the "balloon lumen". The annulus of the balloon lumen preferable contains a relatively stiff wire, placed along a substantial length of the catheter body, that has a tensile strength greater than 60,000 psi to provide sup¬ port and prevent kinking of the catheter body during usage. In the preferred embodiment, the stiffener is tapered at the distal end so that it may provide maximum aid in pushability of the catheter along its proximal end, while at the same time providing added catheter flexi¬ bility at its distal end where the wire is tapered to a smaller diameter. With the stepped or multi-diameter con¬ struction for the wire stiffener, the distal end of the catheter contains sufficient flexibility, thus improving its tractability through tortuous arteries.

The guidewire lumen has a diameter that is adequate to allow free movement of a 0.012" or 0.014" guidewire. This means that this lumen would have an inner diameter of about 0.015-0.020". This lumen adequately provides room to enable the recording of meaningful distal pressures therethrough and the injection of adequate radiographic dyes after removal of the guidewire. The pressure gradi¬ ent across a vascular lesion is a parameter mainly used to assess the adequacy of the results of dilation, a function that is preserved by this very low-profile balloon cathe¬ ter, but which is not provided by similar profile cathe¬ ters currently available.

The free, independent motion of the guidewire al- lows for delicate and unobstructive advancement of the guidewire ahead of the obstructive balloon, a feature which is different from the currently available very low- profile balloon catheters which basicallay feature a fix¬ edly connected guidewire. In addition, the structure provides for the capacity to exchange the guidewire. This also is different from the currently available low-profile balloon catheters that do not allow for removal or rein¬ sertion of a new guidewire or the same guidewire with an adapted tip configuration. It is noteworthy that the currently available very low-profile catheter has to be discarded and replaced in case the tip should become unusable, such as having a stripped coil or severely bent tip, either of which is not an unusual occurrence, result¬ ing in significant increase in cost of the procedure.

The present structure provides also for an exchange of a balloon catheter capacity without need for withdraw- ing the guidewire. In cases where the balloon is not able to pass a lesion or is unable to effectively dilate a lesion already crossed although an improper ballooon is used, the currently available very low-profile catheters need to be withdrawn and the procedure of crossing the lesion must be restarted with a totally new device. The present invention allows usage of exchange guidewires that are typically 300-cm long and kept at the furthermost location reached by the balloon in the vascular anatomy.

The mechanical slider which is disclosed herein is designed to advance, gradually and precisely, a balloon catheter in the guiding catheter, over the guidewre, by using a mechanism that advances the balloon catheter while keeping the guidewire tip in place. The device is man¬ ually activated under fluoroscopic control. When employed in the system, guidewires are recommended that are very stiff in the proximal segment, as well as in the segment just proximal to the balloon, in order to maintain pushing power and to optimize balloon catheter tracking of the guidewire. The mechanical slider is an optional feature and does not have to be used in all cases. It is recommended, however, for difficult progression of the balloon catheter through a severe stenosis.^■ Conditions for' its. ef ective¬ ness are a secure positioning of the guiding catheter in order to achieve optimal support jointly with the stiff¬ ness of the proximal section of the guidewire.;

Brief Description of the Drawings

So that the manner in which the above recited fea¬ tures, advantages and objects of the invention, as well as others which will become apparent, are attained and can be understood in detail, a more particular description of the invention briefly summarized above may be had by reference to the embodiments thereof which are illustrated in the appended drawings, which drawings form a part of this specification. It is to be noted, however, that the ap- pended drawings illustrate only preferred embodiments of the invention and are, therefore, not to be considered limiting of its scope, as the invention may admit to other equally effective embodiments.

In the Drawings:

Figure 1 is a side view of an embodiment of a very low-profile, percutaneous transluminal angioplasty cathe¬ ter in accordance with the present invention.

Figure 2 is a cross-sectional view of the proximal end of the dilating or balloon catheter portion of the embodiment shown in Figure 1, together with a suitable fitting for accessing the guidewire lumen and the coaxial balloon lumen.

Figure 3 is a cross-sectional view of the distal end of the dilating or balloon catheter portion of the embodiment shown in Figure 1, showing the dilating balloon structure attached thereto and illustrated in its inflated condition, and also showing the distal end of a guidewire threaded through the guidewire lumen of the dilating cath- eter. Figure 4 is a side view of a regulated and control¬ led advancement or mechanical slider device attached to the proximal end of the embodiment shown in Figure 1.

Figure 5 is a cross-sectional view taken at line 5-5, shown in Figure 5.

Figure 6 is a sectional view of a preferred embodi¬ ment of the very low-profile, percutaneous transluminal angioplasty catheter in accordance with the present inven¬ tion.

Description of the Preferred Embodiment

Now referring to the drawings and first to Figure 1, an embodiment of a very low-profile, percutaneous transluminal angioplasty catheter system or assembly is shown generally comprising a diagnostic or guiding cath¬ eter 10 and a dilating or balloon catheter 12. The guid¬ ing catheter has a length of approximately 95-110 cm for performing coronary percutaneous transluminal angioplasty on adults. The guiding catheter is made of polyethylene, polyvinyl chloride, polyurethane or nylon material, and may have an outside diameter as small as approximately 0.065" and a wall thickness as small as approximately 0.005". In the embodiment shown, there is formed therein, near the distal end of the guiding catheter, two permanent bends 14 and 16 suitable for use with a left coronary artery. A guiding catheter for use with some other artery would have a different shape. However, it is understood that the catheter is flexible and the shape only enhances its use in connection with a particular application. The proximal end of the guiding catheter is attached to a fin- shaped finger grip 18 or equivalent structure and has an end suitable for receiving a two-part fitting comprising stationary part 20 and swivel part 22.

The proximal end of dilating catheter 12 is secured to fitting 24. Fitting 24 is permanently secured to the proximal end of catheter 12; however, the details of its internal structure are more fully set forth below. A guidewire structure comprising guidewire.26 is. inserted through the central passageway or guidewire lume of dilating catheter 12. In addition, a super, flexible stiffness rod 67, preferably made from nickel-titanium alloy and more clearly shown in Figures 2 and 6, may also be included. As shown in Figure 6, rod 67 is tapered adjacent its distal end so that it may provide maximum stiffness to the proximal end of the catheter body 12, while at the same time allowing tip flexibility at the distal end of the catheter 12, to improve its tracta- bility.

The distal end of dilating cather 12 is attached to a balloon 28 made of a relatively non-distensible mate¬ rial. Such a balloon is typically approximately 2-cm long and is conventionally made of polyethylene, polyethylene terapthalate, or polyvinyl chloride. It is attachable or bonded by means well-known in the art. Actually, the balloon is folded in such a manner that it readily passes through the central lumen of guiding catheter 10 to be unfolded or expanded with the application of pressure thereto in a manner more fully described hereinafter. The distal end of guidewire 26 passes through the guidewire lumen of dilating catheter 12 and extends beyond the dis¬ tal end of such catheter. This distal end 30 of guidewire 26 is more flexible than the guidewire as a whole since it includes a coiled spring 32 and is at a reduced diameter. It also is preferably slightly tapered and rounded at its distal end. Again, guidewire construction for use with dilating catheters are well-known in the art. In advancing guidewire 26 to its eventual location, it should be noted that the distal end 30 thereof is bent to one side and the guidewire itself is rotational by manipulation of its proximal end. Rotation is readily accomplished by way of guidewire manipulator 34. Now referring to Figure 2, the details of the con¬ nection between fitting 24 and dilating catheter 12 are illustrated. The body of fitting 24 is bonded to an elon- gated sheath 58, in turn bonded to the outside surface of external tube 62 of catheter 12.

Fitting 24 includes a side-opening female connec¬ tion 60 that provides connection to the annulus between external coaxial tube 62 and internal coaxial tube 64 of dilating catheter 12. Tubes 62 and 64 are preferably made of polyimid plastic and are approximately 0.028" and 0.016", respectively, in inside diameter dimension or 0.035" and 0.046" for a catheter capable of making distal measurements. Each has a wall thickness in the range of about 0.00075-0.002". As shown in Figure 6, the distal ends of coaxial tubes 62 and 64 are made of a different material than the proximal ends. The distal segment of tube 62 is indicated by numeral 100. The distal segment of tube 64 is indicated by numeral 102. Preferably, seg¬ ments 100 and 102 are made of nylon or any other material having similar stiffness properties, such as polyethylene or polyurethane. A joint 104 is made in the outer tube 62 to connect segment 100 to outer tube 62. Similarly, a joint 106 appears in inner tube 64 to connect it to tube segment 102. As further shown in Figure 6, tube segment 102 further has a taper 108 distally of joint 106 to fur¬ ther reduce the profile of the catheter 12 in the balloon area. The exact location of taper 108 can be as shown in Figure 6 or more distally or more proximally. A band 110 is shown adjacent taper 108 to allow appropriate placement of the balloon for dilation.

Also shown in Figure 6, by example and not by way of limitation, is wire 67 which has a taper 112 so that its distal end is of a lesser diameter than its proximal end. This allows relative rigidity and resistance to kinking throughout the length of the catheter, yet facili¬ tates tip softness. The taper feature of wire 67 can be employed in combination with soft segments 100 and 102 and taper 108 to give the catheter 12 a low profile coupled with tip flexibility to permit tracking in tortuous paths, yet at the same time to provide sufficient body stiffness to resist kinking and to promote pushability. All or^" the above features may be: used in combination or individually to achieve these results.

By example and not: by way of limitation, segment 100 is approximately 25-cm long, and the overall length of tube 64 with segment 102 to the distal extremity of the catheter is approximately 135 cm.

Although polyimid plastic has a tensile strength of approximately 20,000 psi, other plastic materials having a tensile strength of at least 10,000 psi can also be used. Through side connection 60, suitable fluid is pro¬ vided to the coaxial annulus between the tubes for inflat¬ ing the balloon at the distal end of the dilating catheter and for deflating the balloon at appropriate times. That is, removal of the fluid to collapse the balloon is pro¬ vided through connection 20 by equipping the system for a suitable vacuum.

Wedge-shaped end piece 66 of fitting 24 is bonded into the body of the fitting into the end of tube 64 so as to provide a continuous passageway through the fitting contiguous with the central passageway or lumen of dilat¬ ing catheter 12. End piece 66 is also suitably threaded as a female connection for suitable attachment either to cap 68 or to a "Tuohy-Bovsh" connector, as shown in the illustration, or to a suitable external hose or other connection for making contact with the central passageway of the dilating catheter when guidewire 26 has been re¬ moved. Suitable contrast dye can be inserted through this connection and pressure measurements can be made there- through, as desired.

Although not required in all cases, a super elastic rod 67 of nickel-titanium alloy, having an outside diame¬ ter in the range of 0.005-0.008" can be bonded or placed in contact with housing 24 or the end of wedge piece 66. Rod 67 is located in the coaxial annulus between the two coaxial tubes or in the balloon lumen. Approximately th last 1.5 cm of its distal end is preferably tapered an may terminate at the proximal end of the balloon or .5-10 cm proximal to the proximal end of the balloon, as more fully shown in Figure 3. The rod gives stiffness to the shaft of the dilating catheter and prevents any kinks or bends from occurring therein as it is advanced in use.

Alternate structures equivalent to fitting 24 are available and well-known. Therefore, although described as suitable for purposes of this invention, other fitting means are available. Now referring to Figure 3, the distal end of dilat¬ ing catheter 12 and guidewire 26 are illustrated. The distal end of guiding catheter 10 is shown on the left side of the illustration and has a central opening at the exit of its passageway or lumen which is large enough to permit the distal end of coaxial tubes 62 and 64 of the dilating catheter and balloon 28 to pass therethrough. At the time of passage, of course, balloon 28 is appropri¬ ately folded and collapsed. It should be noted that the balloon is secured at the left side of the illustration to outer tube 62 by means well-known in the art and in simi¬ lar fashion to internal tube 64 near its distal end on the right. This provides means by which the balloon is ex¬ panded and collapsed by the application and removal, respectively, of fluid through the coaxial annulus or passageway between the coaxial tube, as shown at reference arrows 68.

Guidewire 26, threaded through the central passage¬ way or guidewire lumen of the dilating catheter, exits at opening 70 thereof. The distal end of guidewire 26 in- eludes a bent tip 30 and a very small coiled-spring por¬ tion 32, which allows the guidewire end to bend just enough to permit convenient positioning into the appropri¬ ately selected arterial branch.

Finally with respect to the illustrations, a preci- sion advancement device or mechanical slider 72 is illus¬ trated in Figures 4 and 5. The device is generally U- shaped and is attached at its front end to fitting portion 22 and at its rear end to the handle of manipulator 34. The long central part of the device is provided with a rack 74 for the advancement of the device with respect to a pinion 76 attached to a fitting 24. Pinion 76 is, in turn, centrally mounted to a thumbscrew 78. Hence, fit¬ ting 24, attached to the dilating catheter, can be ad¬ vanced with precision and accuracy by thumbscrew 78 with respect to fitting piece 22 and hence with respect to guiding catheter 10. Figure 5 shows a cross-sectional view of the end of the advancement device Just described. Fitting 24 is snapped into a square opening in that part of the device which is connected to the pinion. In like fashion, the ends of the advancement device are also received in snap- like fashion in fitting portion 22 and manipulator 34. This permits the device to be readily removed if desired. It should also be noted that the device does not hold manipulator 34 so rigidly as to prevent its rotation or torquing of the guidewire, as previously described. The apparatus which has just been described permits the physician operator to manipulate the guidewire, the dilating catheter and the guiding catheter all indepen¬ dently of one another through appropriate proximal end fittings and the manipulator. The passageways through the fittings provide for accessing the lumens to the guiding catheter and to the dilating catheter for appropriate operation in connection with radio contrast dye and wit respect to appropriate pressure transducer for monitoring the pressure of the respective distal ends of the guiding catheter and the dilating catheter in the manner previ¬ ously described.

While particular embodiments have been shown, it will be understood that the invention is not limite thereto. Many modifications may be made that will becom apparent to those skilled in the art.

Claims

WHAT IS CLAIMED IS:

1. An angioplasty balloon catheter assembly, compris¬ ing

-a balloon-tipped, very low-profile catheter made of plastic material having a tensile strength of at least 10,000 psi and including outer and inner coaxial tubes, defining an outer access annu¬ lar passageway therebetween for inflating and de¬ flating said balloon and an inner access annular passageway for passing a movable and steerable and removable guidewire.

2. An angioplasty balloon catheter assembly in accor¬ dance with claim 1, wherein said outer and inner coaxial tubes are made from polyimid plastic.

3. An angioplasty balloon catheter assembly in accor¬ dance with claim 2, wherein the wall thickness of said outer and coaxial tubes are not more than 0.002".

4. An angioplasty balloon catheter assembly in accor¬ dance with claim 1 and including a stiffness rod located in said balloon access annular passageway.

5. A percutaneous transluminal angioplasty catheter assembly, comprising

-a dilating catheter,

-a balloon attached to the distal end of said dilating catheter, said balloon being made of a relatively non-distensible material,

-said dilating catheter being made of plastic material having a tensile strength of at least 10,000 psi and including outer and inner coaxial tubes defining a balloon access annular passageway therebetween, said balloon access annular passage¬ way providing access for inflating and deflating said balloon, -an annular guiding catheter surrounding said dilating catheter, and

-a guidewire for passing through said, inner coaxial tube of. said dilating catheter.

6. A percutaneous transluminal angioplasty catheter assembly in accordance with claim 5, and including an advancement device ("mechanical slider"), secured to the proximal ends of the guiding catheter, said dilatin catheter said guidewire, to permit gradual precise an secured advancement of said dilating catheter with respect to said guiding catheter over said guidewire.

7. An angioplasty balloon catheter assembly, compris ing a balloon-tipped, very low-profile catheter whos substantial proximal length is made of plastic materia having a tensile strength of at least 10,000 psi and in cluding outer and inner coaxial tubes, wherein the dista ends of said inner and outer coaxial tubes are made of softer material than the proximal lengths of said oute and inner coaxial tubes, said tubes defining an oute access annular passageway therebetween for inflating an deflating said balloon and an inner access annular pas sageway for passing a movable and steerable and removabl guidewire.

8. The catheter of claim 7 wherein the proximal lengt of said inner and outer coaxial tubes is made of polyimi plastic.

9. The catheter of claim 8 wherein said distal ends o said inner and outer coaxial tubes are made of nylon.

10. An angioplasty balloon catheter assembly in accor dance with claim 9, wherein the wall thickness of sai outer and coaxial tubes are not more than 0.002".

11. An angioplasty balloon catheter assembly in accor¬ dance with claim 7 and including a stiffness rod located in said balloon access annular passageway.

12. The catheter of claim 11 wherein said stiffeness rod is tapered to a smaller diameter near its distal end.

13. An angioplasty balloon catheter assembly in accor¬ dance with claim 9 and including a stiffness rod located in said balloon access annular passageway.

14. The catheter of claim 13 wherein said stiffeness rod is tapered to a smaller diameter near its distal end.

15. A percutaneous transluminal angioplasty catheter assembly, comprising

-a dilating catheter,

-said dilating catheter having its substantial proximal length made of plastic material having a tensile strength of at least 10,000 psi and includ- ing outer and inner coaxial tubes, wherein the distal ends of said inner and outer coaxial tubes are made of a softer material than the proximal lengths of said outer and inner coaxial tubes, said tubes defining a balloon access annular passageway therebetween, said balloon access annular passage¬ way providing access for inflating and deflating said balloon,

-an annular guiding catheter surrounding said dilating catheter, and -a guidewire for passing through said inner coaxial tube of said dilating catheter.