WO1998014233A1

WO1998014233A1 - Inflatable tube for dilating catheter and method of manufacture

Info

Publication number: WO1998014233A1
Application number: PCT/FR1997/001730
Authority: WO
Inventors: Georges Boussignac; Pierre Hilaire
Original assignee: Laboratoires Nycomed S.A.
Priority date: 1996-10-02
Filing date: 1997-10-01
Publication date: 1998-04-09
Also published as: FR2753907A1; JP2001501115A; FR2753907B1; EP1009469A1

Abstract

The invention concerns an inflatable tube for dilating catheter and its method of manufacture. This tube consists of a wall of substantially uniform thickness defining a generally cylindrical central portion connecting two generally tapered end portions characterised in that the said wall comprises at least one series of indentations distributed over said central portion and/or over said end portions, said indentations, and particularly those distributed on the central portion of the tube, being capable of being levelled out by the inflating of the air bag beyond a predetermined pressure, preferably close to the normal pressure for using the tube. The invention is useful for transluminal coronary angioplasty and for treating infections of various ducts of the human or animal body.

Description

Balloon for dilatation catheter and method of making the same

The present invention relates to a new balloon for dilatation catheter and its manufacturing process. The invention mainly finds application in the field of transluminal coronary angioplasty, and can be more generally used in the field of the treatment of affections of various conduits of the human or animal body, such as for example the urinary conduits and in particular the urethra , or even digestive and in particular the esophagus. The narrowing of the blood lines (vessels, arteries or veins) is the cause of serious circulation problems, and various techniques have been developed to prevent such conditions.

These techniques notably call for the use of a dilatation catheter carrying at its distal end an inflatable expander element, called a balloon or balloon.

As part of the technique called transluminal coronary angioplasty, a dilation catheter is inserted inside a coronary artery, to arrange the balloon at the level of the stenosis. The balloon is then inflated to a relatively high and predetermined pressure, so as to compress the stenosis in the wall of the artery and thus restore the normal section of passage of said artery at the level of the stenosis.

A balloon dilation catheter can also be used for the installation, inside the stenosis duct, of a device commonly designated by the American term "stent", intended to restore, or maintain, the normal section of passage of the duct at the level of the stenosis.

Such stents generally comprise an elongated radially expandable frame between a first constricted state of reduced diameter and a second expanded state where said frame has a diameter substantially equal to the natural diameter of the bodily duct to be treated. In their simplest configuration, these stents consist of one or more elements formed of a deformable metal wire with low elastic memory wound on itself according to a helical curve around a balloon, the expansion being forced mechanically under the effect of inflating said balloon. In general, a balloon for a dilatation catheter is constituted by a wall of substantially uniform thickness defining a substantially cylindrical central portion connecting between them two end portions of generally frustoconical shape. Such a balloon is usually produced from a tubular blank of small size inflated and stretched inside a mold until the desired shape is obtained.

The balloons used so far have both a substantially smooth surface at their central portion and at their end portion. In their implementation, the balloon dilatation catheters pose different problems, such as for example problems of gliding at the level of the bodily conduits to be treated, or again problems of space, resulting from an imperfect folding of the balloon, during the withdrawal of the catheter after treatment.

Furthermore, when used for the placement of a stent, the balloons, due to their particular conformation, tend to tighten the stent during inflation by creating a ferrule, likely to cause more or less damage. less important of the vessel wall to be treated.

Under these conditions, the aim of the present invention is to solve the technical problem consisting in the supply of a balloon for dilation catheter of a new design, which, when it is used in the various treatments mentioned above, does not not the disadvantages of the balloons used to date.

It has been discovered, and this constitutes the basis of the present invention, that it was possible to avoid the drawbacks resulting from the traditional conformation of the balloons for catheter of dilation, by forming in the wall of these, retractable impressions whose conformation is precisely studied to facilitate the implementation of the balloon in its different applications.

Thus, according to a first aspect, the subject of the present invention is a balloon for dilatation catheter constituted by a wall of substantially uniform thickness defining a central portion of generally cylindrical shape connecting between them two end portions of generally frustoconical shape, characterized in that said wall comprises at least one series of imprints distributed over said central portion and / or over said end portions, said imprints, and in particular the imprints distributed over the central portion of the balloon, being able to be flattened under the effect of the inflation of said balloon beyond a predetermined pressure, preferably close to the normal pressure of use of the balloon.

Thus, as can be understood, the balloon in the position of use has the usual form of balloons used to date and therefore behaves in an identical manner.

According to a first embodiment of the invention, the abovementioned imprints are shaped to allow easy and stable positioning of the balloon in a body conduit. To this end, said imprints can be in extremely varied forms, the determining element being to confer, at least on the central portion of the balloon, an irregular surface state, the irregularities constituting anchoring points of the balloon to the wall of the body duct to be treated ensuring easy and stable positioning of the balloon. Preferably, the abovementioned imprints will be in the form of bosses or toric grooves, bosses or helical grooves, an embossing or else of bumps distributed, preferably regularly, over a major part of the surface of the central portion of the balloon.

According to a second embodiment of the invention, the abovementioned imprints are shaped to facilitate regular expansion of a stent during its placement using a balloon dilatation catheter.

To this end, the imprints will preferably be made in the form of a continuous or discontinuous helical boss extending over a major part of the surface of the central portion of the balloon. According to a third embodiment of the invention, the aforementioned imprints will be shaped to facilitate folding and folding of the balloon.

To this end, the imprints will be shaped to constitute bending caps and will preferably be in the form of grooves extending longitudinally at the end portions of the balloon and possibly at the level of the central portion.

Such grooves can have various profiles and in particular U or V profiles.

According to a second aspect, the subject of the present invention is a method for manufacturing a balloon for a dilatation catheter as defined above. This process comprises, in a manner known per se, the steps consisting in: - extruding a thermoplastic material to form a substantially tubular blank;

- Hot stretching said blank longitudinally and expanding it radially inside a mold to orient said thermoplastic material biaxially, and is characterized by the fact that said mold has on its internal wall imprints of shape complementary to those of the imprints desired on the ball.

The invention will be better understood, and other objects, characteristics and advantages thereof will appear more clearly on reading the explanatory description which will follow, made with reference to the appended schematic drawings given solely by way of nonlimiting examples illustrating several embodiments of the invention, and in which:

- Figure 1A is a schematic view in longitudinal section illustrating the problems of positioning in a body conduit of a balloon for dilatation catheter according to the prior art;

- Figure 1B is a view similar to Figure 1A of a balloon according to an embodiment of the present invention for solving this positioning problem; - Figure 2A is a schematic view in longitudinal section illustrating the establishment of a stent using a balloon according to the state of the art and the problems of sliding of the stent resulting therefrom;

- Figure 2B is a view similar to Figure 2A of a balloon according to an embodiment of the present invention to solve this problem;

- Figure 3A is a schematic view of a balloon according to the present invention comprising imprints in the form of toric bosses;

- Figure 3B is a view similar to Figure 3A of an alternative embodiment of the balloon in which the imprints are in the form of toric grooves;

- Figure 3C is a view similar to Figure 3A of an alternative embodiment of the balloon in which the imprints are in the form of a helical boss; - Figure 3D is a view similar to Figure 3A of an alternative embodiment of the balloon in which the imprints are in the form of bumps;

- Figure 3E is a view similar to Figure 3A of an alternative embodiment of the balloon in which the imprints are in the form of an embossing;

- Figure 4 is a view similar to Figure 3A of an alternative embodiment of the balloon in which the imprints are in the form of longitudinal grooves; - Figure 4A is a sectional view along line AA of Figure 4;

- Figure 4B is a view similar to Figure 4A showing the balloon during its folding phase.

The principle on which the present invention is based makes it possible to solve various problems of positioning or using balloons for a dilatation catheter.

Three possibilities of using the present invention will be more particularly described in the following.

With reference to FIGS. 1A and 1B, a first embodiment of the invention will be described which makes it possible to prevent the problems of positioning a balloon in a body conduit.

It is known that the thermoplastic materials commonly used for the manufacture of balloons pose problems of "sliding" at the level of the bodily conduits into which these balloons are introduced. To avoid these problems, balloons are generally coated with a hydrophilic material intended to improve gliding. However, the installation of a balloon thus coated is difficult because of the risks of slipping during inflation, as can be understood with reference to FIG. 1A.

In this figure, the reference numeral 1 designates a bodily conduit such as a blood conduit, the numeral 2 representing a stenosis. As can be seen, a traditional balloon coated with a hydrophilic material 3 has, during inflation, a shape similar to that of a suppository and tends to slide in the duct due to this shape and its coating. This problem can be avoided by using, in accordance with the present invention, a balloon, whether or not coated with a hydrophilic material, the central part of which at least in the positioning phase has an irregular surface state.

In the example shown in FIG. 1B, the wall of the balloon 3 (also shown in FIG. 3A) comprises, at its central portion, a set of toric bosses 4 preferably distributed evenly and forming a set of anchor points of the balloon to the wall of the body conduit 1 to be treated, thus guaranteeing an easy and stable positioning of said balloon at the level of the stenosis 2. Of course, other embodiments are possible to achieve this result and in particular those which are shown in FIGS. Figures 3B to 3E.

In the variant embodiment shown in FIG. 3B, the imprints are in the form of toric grooves preferably distributed evenly over a major part of the surface of the central portion of the balloon. In the variant embodiment shown in FIG. 3C, these imprints are in the form of a helical boss which can be continuous or discontinuous, single or multiple.

In the alternative embodiment represented in FIG. 3D, the imprints are produced in the form of bumps each having substantially the shape of a bowl, and which can be distributed over a major part of the surface of the central portion of the balloon, for example along longitudinal lines, the bumps of each line being regularly spaced from one another and offset longitudinally from the bumps of the neighboring line.

In the variant embodiment shown in FIG. 3E, the imprints are in the form of rectangular parallelepipeds obtained by embossing. These shapes are designated in this description by the term embossing.

With reference to FIGS. 2A and 2B, a second embodiment of the invention will now be described which makes it possible to solve the problems of placing a stent in a body conduit such as a blood conduit. Due to its shape and in particular the presence of extreme portions of generally frustoconical shapes, a traditional balloon around which a stent has been wound tends, during inflation, to compress the stent in its central part, thereby creating a ferrule as understood with reference to Figure 2A. In this figure, the reference numeral 5 designates a stent of traditional shape.

The balloon according to the present invention and shown in Figure 2B allows regular deployment of the stent in a body channel and easy positioning of this stent without any risk of longitudinal sliding.

To this end, the balloon is provided with a helical boss which can be continuous or discontinuous, the turns of this boss making it possible, as we understand, to obtain a guided deployment of the stent.

FIGS. 4 and 4A show a third embodiment of the invention which makes it possible to solve the problems of folding and folding the balloon, in particular during the withdrawal of the catheter.

To this end, a balloon in accordance with the present invention can be provided with a set of longitudinal grooves extending at least over the end portions of the balloon and possibly over the central part of the latter. As can be understood, these grooves form primers for folding the balloon (see FIG. 4B) and promote not only the folding of the balloon before its introduction into a body conduit, but also the folding of the latter during removal after an intervention.

Such grooves can have various profiles and in particular a U-shaped profile (see FIG. 4A) or even a V-shaped profile.

Of course, the wall of a balloon in accordance with the present invention can be provided with several different series of imprints, each series of imprints being intended to prevent or solve one of the three problems explained above. The balloons according to the invention which have just been described can be produced relatively easily by a process consisting in:

- extruding a thermoplastic material to form a substantially tubular blank;

hot stretching said blank longitudinally and expanding it radially inside a mold to orient said thermoplastic material bi-axially, said mold having on its internal wall imprints of a shape complementary to those of the imprints desired on the balloon. This process differs from the processes usually used for the manufacture of balloons, only by the imprints carried by the mold shells.

The thermoplastic materials which can be used for the manufacture of the balloons in accordance with the invention are in particular polyethylene, polyethylene terephthalate, polyamides and polyamide copolymers.

For a more detailed description of the steps known per se of the process according to the invention, reference may be made to the existing state of the art and in particular to US Patent No. 4,490,421 incorporated here by reference. The imprints of the balloon thus obtained are capable of being flattened under the effect of the inflation of said balloon beyond a predetermined pressure, preferably close to the normal pressure of use.

For this purpose, the imprints have dimensions slightly smaller than the maximum stretching dimensions of the material. This gives areas of less stretch which have a higher elongation potential than the other areas and which therefore make it possible to find a smooth surface from a certain pressure. As can be understood, the balloons are initially inflated to a pressure slightly lower than the normal pressure of use (for example of the order of 1 to 6 bars). Under these conditions, the balloon reproduces the imprints of the mold.

When the balloon is inflated to a higher pressure, close to the operating pressure (8 to 16 bars), these imprints disappear and the balloon resumes a cylindrical shape in its central part and frustoconical in its end portions.

Claims

1. Balloon for dilatation catheter, constituted by a wall of substantially uniform thickness defining a central portion of generally cylindrical shape connecting between them two end portions of generally frustoconical shape, characterized in that said wall comprises at least one series of footprints distributed over said central portion and / or over said end portions, said footprints, and in particular the footprints distributed over the central portion of the balloon, being able to be flattened under the effect of the inflation of said balloon beyond a predetermined pressure, preferably close to the normal pressure for using the balloon.

2. Balloon according to claim 1, characterized in that the aforementioned imprints are shaped to allow easy and stable positioning of the balloon in a body conduit and confer, at least on the central part of the balloon, an irregular surface state.

3. Balloon according to claim 2, characterized in that the abovementioned imprints are in the form of bosses or toric grooves, bosses or helical grooves, an embossing or else distributed bosses, preferably in a regular manner, over a major part of the surface of the central portion of the ball.

4. Balloon according to claim 1, characterized in that the aforementioned imprints are shaped to facilitate regular expansion of a stent during its implementation using a balloon dilatation catheter.

5. Balloon according to claim 4, characterized in that the impressions are made in the form of a continuous or discontinuous helical boss extending over a major part of the surface of the central portion of the balloon.

6. Balloon according to claim 1, characterized in that the aforementioned imprints are shaped to facilitate folding and folding of the balloon by forming folding primers.

7. Balloon according to claim 6, characterized in that the aforementioned imprints are in the form of grooves extending longitudinally at the end portions of the balloon and optionally at the level of the central portion.

8. Balloon according to claim 7, characterized in that the aforementioned grooves have a U or V profile.

9. A method for manufacturing a balloon for a dilatation catheter as defined in any one of claims 1 to 8, of the type consisting in: - extruding a thermoplastic material to form a substantially tubular blank;

hot stretching said blank longitudinally and expanding it radially inside a mold to orient said thermoplastic material biaxially, characterized in that said mold has on its internal wall imprints of shape complementary to those of the imprints desired on the ball.