WO1990008567A1

WO1990008567A1 - An angioplasty catheter and a method of making the same

Info

Publication number: WO1990008567A1
Application number: PCT/CA1990/000027
Authority: WO
Inventors: Goeffrey S. Martin
Original assignee: Vas-Cath Incorporated
Priority date: 1989-01-30
Filing date: 1990-01-30
Publication date: 1990-08-09
Also published as: CA1329090C; AU4967990A

Abstract

An angioplasty catheter (20) having a body (22) formed initially from an extrusion having dual lumens (34, 36) and which is then drawn through a die to reduce the cross-section thereby enhancing the surface finish and molecular orientation of the body. The result is a catheter having a main body of minimized crossed-section with good strength, torque, stiffness and resistance to kinking characteristics.

Description

DESCRIPTION AN ANGIOPLASTY CATHETER AND A METHOD OF MAKING THE SAME

TECHNICAL FIELD This invention relates to angioplasty catheters for use in the treatment of stenosed blood vessels. The invention also relates to a method of manufacturing the catheter.

An angioplasty catheter is typically elongate and tubular, and is provided with a balloon near or at its distal end and radiopaque bands defining the extremities of the balloon. The catheter is inserted at a convenient location and fed into the stenosed blood vessel until the balloon is located in the narrowed portion of the blood vessel. Fluid from an external supply is then used to inflate the balloon such that it compresses the obstructing plaque and stretches the plaque coated walls of the blood vessel. When the physician is satisfied that the blood vessel has been widened sufficiently, the balloon is deflated and the catheter removed.

BACKGROUND ART

Angioplasty catheters have been successfully used for a number of years in the treatment of blood vessels obstructed or stenosed with plaque. An angioplasty catheter includes, near its distal end, a balloon which can be inflated by means of pressurized fluid supplied through a lumen in the catheter. The treatment involves the location of the balloon in the stenosed section of the blood vessel, followed by inflation and deflation. During inflation, the balloon compresses the plaque and stretches the blood vessel such that the cross-sectional area of the stenosis is increased until it is comparable to.that of the unobstructed blood vessel. When the treatment has been completed the balloon is deflated and the catheter removed. The treated blood vessel maintains substantially its enlarged cross-section to permit the free flow of blood through this portion.

To perform satisfactorily a suitable angioplasty catheter must possess a number of properties. For ease of insertion it is preferable that the catheter is flexible, has a relatively small cross-sectional area, and has a smooth outer surface. Also, the method of insertion of the catheter has a significant bearing on the form of the catheter. The catheter which is the subject of the present invention is intended for insertion using the Seldinger technique and therefore preferably has a tapered end and a lumen to receive the Seldinger guide wire. The catheter ends at an aperture in the tapered end substantially coaxially with the main body of the catheter. However, perhaps the most important part of the catheter is the balloon which must be strong enough to withstand the application of high pressures without rupture and which must always inflate to a predetermined shape and size.

With reference to the size of the catheter, it is desirable to minimize the cross-section of the body while meeting the requirements of strength, stiffness, resistance to kinking, torsional rigidity, and surface smoothness needed to enter and feed the long catheter through the veins or arteries from an access point remote from the stenosis. This conflicts with another requirement which is the need to make connections to the body at the proximal end and to attach the bulb satisfactorily near the distal end.

DISCLOSURE OF INVENTION

It has been found that these conflicting design requirements can be met in the present novel design in which the body is formed initially from a dual lumen extrusion of a diameter which is as small as is practical for making the proximal end attachments, and which is then drawn through a die to reduce the diameter and at the same time enhance the surface finish and molecular orientation of the body. The result is a catheter having a main body of minimized crossed-section with good strength, torque, stiffness and resistance to kinking characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a perspective view of an angioplasty catheter in accordance with a preferred embodiment of the present invention; Fig. 2 is an enlarged isometric view of a balloon forming part of the catheter;

Fig. 3 is a sectional view on line 3-3 of Fig. 1;

Fig. 4 is a sectional view on line 4-4 of Fig. 1; Fig. 5 is a diagrammatic sectional view illustrating the drawing of the main body to reduce cross-section and to change the physical characteristics of the main body of the catheter;

Fig. 6 is a sectional view illustrating the method of manufacturing a tip on the catheter;

Fig. 7 is a diagrammatic sectional view illustrating a method of manufacturing the balloon; and

Figs. 8 to 11 are views, mostly in section, illustrating the method of manufacturing the junction at the proximal end where tubes provide access for a Seldinger wire and for providing a supply of fluid to inflate the balloon.

BEST MODE FOR CARRYING OUT THE INVENTION

The preferred embodiment of the angioplasty catheter according to the present invention will now be described in detail, firstly with reference to Fig. 1 of the drawings. This view shows in perspective an angioplasty catheter, designated generally by the numeral 20, including a flexible main body 22 having a distal end 24 defining a tapered tip 25 to facilitate insertion into a vein of a patient, and a proximal end 26 for connection, by means of connection piece 28, to the respective distal ends of a guide wire tube 30 and a fluid supply tube 32. The tubes 30, 32 are in communication with respective circular guide wire and fluid supply lumens 34, 36 defined within the main body 22 (Fig. 3) and are provided with luer fittings 35, 37 at the respective proximal ends. Different coloured marking sleeves 38, 39 help distinguish the tubes from one another (although in practice the fluid supply lumen 36 is of significantly smaller cross-section than lumen 34). The body 22 extends from the connection piece 28 to the tip 24 and passes through a balloon 40, details of which are provided below. A tubular shipping protector (not shown) for location over the distal end 24 and balloon 40 would normally be provided to protect the balloon and to retain it in a collapsed condition ready for insertion.

Reference is now made to Fig. 2 of the drawings which shows the distal end of the catheter in greater detail with the balloon in a collapsed condition. The balloon 40, located at the distal end 24, is formed of a Nylon membrane which is flexible and substantially inextensible (i.e. not elastomeric) and, when inflated, is in the form of a cylinder having tapering ends (as indicated in ghost outline). The distal and proximal ends 46, 48 of the membrane locate snugly over the distal end 24 of the main body 22 with the distal end 46 being mated to the body just short of the tapered tip 25. An side opening or aperture 50 in the wall of the main body 22 provides fluid communication between the smaller fluid supply lumen 36 and the interior of the balloon 40 between the body 22 and the membrane of the balloon.

A pair of radiopaque bands 54, 55 are attached around the body 22 inside the balloon 40 and near the ends 46, 48 for monitoring the position of the balloon. To inflate the balloon 40, fluid is supplied under pressure through the fluid supply tube 32 and the fluid supply lumen 36, and then through the aperture 50 into the balloon 40. Thus, the balloon is pushed radially outwardly by the fluid pressure to assume the shape shown by the chain-dotted lines in Big. 3, so that the balloon 40 has a diameter greater than that of the main body 22. On deflation, and on withdrawing the fluid by suction (i.e. negative pressure) the balloon folds and collapses to lie close to the outer surface of the body, as shown in Figs. 2 and 4. Reference is next made to Fig. 5 which illustrates diagrammatically how the main body 22 is drawn down. As seen in Fig. 1, the main body meets, adjacent the connection piece 28, a short portion 56 of larger diameter than the main body 22. This corresponds to the diameter at portion 58 in Fig. 5 and a diameter 60 corresponds to that of the main body. The purpose of this reduction in diameter will be explained in more detail later but for the moment it is sufficient to understand how it is accomplished. A length of extruded Nylon having a cross-section similar to that shown in Fig. 3, but of the diameter of portion 58, is first cut to remove some material to leave a leading end piece 62. This piece is small enough to pass readily through an opening 64 in a heated die 66. A pair of supporting rods 68, 70 are engaged in the respective lumens 34, 36 (Fig. 3) and have proportions corresponding to the required sizes of these lumens as drawn in Fig. 3. Of course the rods will be loose in the original extrusion because it is of larger size than the body 22. The die 66 includes a conical lead-in portion 72 which blends smoothly into the polished opening 64, and at the outlet, a rounded nose portion 74 is provided so that after extrusion, the body can be drawn backwards through the die to remove it. After cutting the extrusion to provide the end piece 62, the rods 68, 70 are engaged and the end piece 62 fed through the heated die to be used to draw the remaining extrusion through the die. This drawing process takes place to effectively orientate molecular structure, improve the surface finish, and enhance the density of the Nylon to give it better torsional stiffness and strength. This continues in the manner illustrated in Fig. 5 until the portion 56 (Fig. 1) is reached, at which point the drawing is discontinued and the body is withdrawn in the opposite direction from the die 66. An end part, including the leading end piece 62, is cut off the extrusion leaving only,the required part of the body. The length of the catheter can be fixed at this stage.

The next step in the process is to form the tip 25 (Fig. 1) and the method of doing this is illustrated diagrammatically in Fig. 6. Here a heated die 76 has an internal shape corresponding to that of the required tip and an opening 78 aligned with the tip to receive an end part of the mandrel 80 which is engaged through the guide wire tube of the body. A rod or mandrel 82 is provided in the fluid supply tube and, under the influence of heat from the die 76, the body is advanced into the die and deformed into the shape shown in Fig. 6. It will be seen in this Fig. that the fluid supply tube has been terminated at its end whereas the guide wire tube has been retained in an open condition to provide access for the Seldinger wire during insertion. The form of the structure is such that the end is conical so that the Seldinger wire is centered relative to the catheter during insertion.

As a separate procedure, a membrane is formed to be used to make the balloon. This procedure is illustrated diagrammatically in Fig. 7. A tube of Nylon having a wall diameter thickness of about 0.015 inches is located in a copper mould 84 made up of two halves 86, 88. The tube 56 is cut at a lower end 90 and a clamp 92 is attached to a short end piece 94 which extends from the mould 84 to seal the end of the tube and to ensure that the tube is not pulled from the mould. The tube and mould are then suspended in a heated oil bath 96 at about 170° to 175°C for three minutes. The total weight of the mould and accessories is about 150gm. and this weight tends to stretch the heated tube such that the molecular orientation becomes axial along the length of the tube.

After three minutes in the oil bath 96 a pressure of 400 p.s.i. is applied to the inside of the tube from an external supply (not shown) causing it deform to occupy the interior of the mould, oil in the mould being pushed from the mould through relief holes 98. After a short interval of time the pressure is released and the mould containing the resulting membrane 100 is removed from the oil bath and placed in freon which acts as a coolant and disperses the oil. The membrane retains the tapered cylindrical shape of the mould, the deformed portion having a wall thickness in the order of 0.00025 to 0.0005 inches.

Reference is next made to Fig. 8 which is the first of a series of Figs. 8 to 12 demonstrating the manufacture of the connection piece 28 shown in Fig. 1. The portion 56 of the main body is held in place to receive, under the influence of some heat, a pair of mandrels 102, 104. These mandrels have leading ends corresponding to the sizes of the respective guide wire tube 30 and fluid supply tube 32, and leading end portions 106, 108 are conical with the axis inclined as indicated by the chain dotted center lines to meet cylindrical portions 110, 112 of the mandrels. This arrangement is necessary since they are to be used to form an end of the main body and deformation can only take place outwardly. The mandrels are entered into the lumens 34, 36 to the position shown generally in Fig. 9 where it will be seen that the ends of the lumens have been flared. Next, and as seen in Fig. 10 diagrammatically, the distal ends of the respective guide wire tube 30 and fluid supply tube 32 are engaged in the flared ends of the lumens 34, 36 followed by a pair of suitably proportioned mandrels 114, 116 which are engaged through the tubes and into the body portion 56. The tubes and body are of Nylon which is a thermoplastic material so that deformation of these parts can be achieved to bring them together in a single assembly.

As seen in Fig. 11, a thin sleeve 118, of a Nylon material is engaged over the body portion 56 and extending outwardly beyond this portion terminating around the tubes 30, 32. Over this is applied a heavy sleeve 120 of silicon rubber which is stretched into place. The assembly is then heated and compressed in a suitable clamping arrangement such as a pair of formed die halves (not shown) to bring the materials into flowing engagement with the mandrels and to seal the Nylon parts to one another. The silicon rubber sleeve 120 helps to distribute the load and to apply a circumferential compressive loading on the parts to cause flowing around the mandrels.

The resulting structure looks generally like that shown in Fig. 12. The tubes 30, 32 are supported where they meet the connection piece and the internal surfaces are smooth since they were formed around the mandrels 114, 116 which of course are withdrawn after the procedure is completed.

The procedure described with reference to Figs. 8 to 12 can be varied by using different sleeve arrangements and even by building up several sleeves one over another to provide more material flowing and to enhance the strength of the structure.

INDUSTRIAL APPLICABILITY

The resulting catheter 20 (Fig. 1) has retained the necessary sizing to perform the asembly shown in Figs. 8 to 12 while at the same time resulting in a main body of reduced diameter thereby meeting the conflicting desirable design criteria for manufacturing angioplasty catheters. The resulting body is not only smaller in diameter but is a more constant diameter and is enhanced due to the molecular orientation resulting from drawing and the enhanced surface finish provided by the polished die through which the body was drawn. The small diameter catheter has substantially the same strength characteristics both in torsion and flexibility achieved by the general extrusion so that it is not of any diminished capability but on the contrary, has improved characteristics desired by practioners in using these devices.

In the preferred embodiment the main body has an outside diameter of 5 French (about 0.0065 inches) which is drawn from about 5.5 French with guide wire lumen about 0.037 inches and fluid supply lumen about 0.017 inches, The portion 56 (which corresponds to the original extrusion) is 7 French (about 0.090 inches), and the lumens 0.039 and 0.024 inches in diameter.

This embodiment and others are within the scope of the invention as defined and claimed.

INDEX OF REFERENCES SIGNS

Claims

CLAIMS:

1. An angioplasty catheter (20) comprising an elongate main body (22) defining guide wire and fluid supply lumens (34, 36) and terminating at a distal end in a tapered tip (25), the fluid supply lumen being closed at the tip and the guide wire lumen extending to the tip for receiving a Seldinger wire to guide the catheter during insertion procedures, the main body defining a side opening (50) meeting the supply lumen near the tip; a balloon (40) sealed to the main body near the tip and containing said side opening, the balloon being of a non-elastomeric material and having a defined shape when inflated by fluid pressure applied through the supply lumen; the main body having a portion of larger cross-section (56) at the proximal end of the main body and formed integrally with the main body of thermoplastic material; guide wire and fluid supply tubes (30, 32) and a connection piece (28) at the proximal end of said portion and connecting the tubes to said portion, characterised in that said portion of the main body is an extrusion and the main body is formed from the extrusion by drawing the extrusion through a heated die while supporting the lumens to give the main body a reduced cross-section, longitudinal molecular orientation, and enhanced surface smoothness.

2. A catheter as claimed in claim 1 and further comprising a pair of raidopague bands on the body (22) and within the balloon (40).

3. A catheter as claimed in claims 1 or 2 in which said defined shape is essentially cylindrical.

4. A catheter as claimed in claim 1 or 2 in which the body (22) has a substantially circular cross-section.

5. A catheter as claimed in claims 1 or 2 in which the guide wire lumen (34) is substantially larger cross-section than the supply lumen (36).

6. A catheter as claimed in claim 1 or 2 in which the body (22) has a substantially circular cross-section and which the lumens (34, 36) are also of circular cross-section.

7. A method of making an angioplasty catheter (20) having a main body (22), a connection piece (28) at a proximal end of the main body and connecting the main body to a guide wire tube (30) and to a fluid supply tube (32), a balloon (40) near the distal end of the main body and in fluid communication with the fluid supply tube at an aperture (50), the method being characterized by making the main body from an oversized extrusion and drawing the extrusion to a smaller cross-section to improve the surface finish and orientate the molecular structure longitudinally of the main body.