WO2004058317A1

WO2004058317A1 - Method for fastening an elastic silicone-comprising jacket to a stent

Info

Publication number: WO2004058317A1
Application number: PCT/EP2003/012544
Authority: WO
Inventors: Michael Denzner; Franz Poersch; Georg Kühlein
Original assignee: Raumedic Ag
Priority date: 2002-12-30
Filing date: 2003-11-11
Publication date: 2004-07-15
Also published as: AU2003296569A1; DE10261728A1

Abstract

The invention relates to a method for fastening an elastic silicone-comprising jacket to a stent that can be converted from a contracted state to an expanded state by supplying heat. According to the inventive method, the jacket is converted from an initial state into an expanded state and the jacket and the stent are fit into each other in the contracted state of the stent. The jacket is then converted from its expanded state to a shrunken state in which it rests at least in some sections closely against the stent by supplying energy, preferably heat. In order to simplify this method and reduce costs, the jacket is converted from its initial state to its expanded state by mechanically expanding it while supplying heat and is cooled before stent and jacket are fit into each other. The shrink rate of the jacket in the radial direction is less than 2:1, preferably 1.1 to 1.2:1.

Description

Method for applying an elastic, silicone-containing sheathing on a stent

The present invention relates to a method for applying an elastic, silicone-containing sheathing on a stent which can be converted from a contracted to a spread state by supplying heat, in which the shroud is converted from an initial state to an expanded state and the sheath is in the contracted state of the stent and stent are pushed into one another and then the sheathing is transferred from its expanded state to a shrunk state by supplying energy, preferably heat, in which it rests at least in sections on the stent.

Methods for sheathing vascular supports are known from the prior art. These stents, also known as stents, are used in the treatment of vascular occlusions. Pathological narrowing of the occlusions or blood vessels, known as stenoses, causes a circulatory disorder in the organs or extremities to be supplied. Circulatory disorders of this kind can have serious consequences. The reduction in blood flow is shown in the form of pain, it can also come to a complete standstill, which can trigger a heart attack or stroke, for example. For the treatment of stenoses, the stents are introduced into the patient's blood vessels in a known manner. The vascular supports can be formed by a metallic, essentially tubular base body. In order to avoid injury to the blood vessel, the stents are surrounded with an elastic, tubular sheath.

In the known methods, the vascular support itself consists of an essentially tubular, metallic base body. The base body is mesh or lattice-shaped and is in a contracted state before being introduced into the bloodstream. In this state, the elastic covering is also applied to the stent. In the initial state, the casing has an inner diameter that is less than or equal to the outer diameter of the stent in the contracted state. In the known methods, the casing consists of a swellable material and is subjected to a swelling process before being attached to the stent. The jacket expands so that the inside diameter of the jacket is larger than the outside diameter of the stent. In the expanded state of the sheath, the stent can be inserted into the sheath. After the covering has been applied, the swelling process is reversed, so that the inside diameter of the covering decreases and the covering thus rests on the vascular support under a certain pretension.

The previously known methods are currently complex and therefore expensive; 'This proves to be disadvantageous, particularly in the mass production of stents. The queuing process cannot always be precisely controlled.

The object of the invention is therefore to provide a method of the type mentioned at the outset which, compared to conventional methods, enables simplification and better reproducibility of the application of an elastic jacket to a stent.

The object is achieved according to the invention in that the casing is transferred from its initial state to its expanded state with the addition of heat and is then fixed in its expanded state by cooling. After the stent and the sheath have been put together, heating is carried out again, the sheath shrinking onto the stent. The shrinkage rate of the sheathing in the radial direction is less than 2: 1, preferably 1.1 to 1.3: 1, in the axial direction less than 1.3: 1, preferably 1.03 to 1.11: 1.

This solution is simple and has the advantage that, compared to conventional solutions, the elastic covering can be expanded quickly and evenly, and the covering can shrink in a controlled manner while the covering is being attached to the stent. It is no longer necessary to carry out lengthy swelling processes. The method according to the invention can now be carried out using shrink sleeves. Of particular importance here is the low shrink rate of the shrink tube. Conventional shrink sleeves have a shrink ratio of approximately 3: 1. This means that the shrink sleeve is expanded, for example, to 3 cm outside diameter during manufacture. When shrinking back under the influence of heat, it goes back to 1 cm outside diameter. The shrink rate of 3: 1 is calculated from this.

Conventional shrink sleeves or jackets with a shrink rate of approximately 3: 1 are completely unsuitable for attachment to a stent. Since the vascular support with the sheath is inserted into a bloodstream after the sheath is mounted on the stent, the stent and thus the sheath also expands. The high shrinkage rate of the sheathing creates very high tensions, which either make it impossible to expand or pull the expanded stent together again over time, so that it loses its supporting effect.

In contrast, the significantly lower shrink rate of the method according to the invention results in a significantly lower pretensioning of the casing. It has been shown that, on the one hand, the low shrinkage rate of the sheathing used enables simple assembly and, on the other hand, the functioning of the stem can be guaranteed even after it has been introduced into the bloodstream and the vascular support has expanded.

Such shrink sleeves with a shrinkage rate of 2: 1 or below have not been commercially available and are not described in the literature. This is because for the usual shrink tube applications, an optimal hold of the sheath on the article to be shrink-wrapped is desired, which can only be achieved by prestressing the shrink tube as high as possible and thus a high shrink rate.

In the case of vascular support sheathing using shrink tubing, high prestressing is not tolerable for functional reasons - as has already been described - rather, one must be attached to the vascular support and the intended application. appropriately adapted, i.e. low pretension. The procedural parameters for producing the sheathing with a prestress, which ensures that the sheathing is adequately held on the stent without loss of function of the stent, on the one hand, in combination with the relative dimensions of the sheathing in relation to the stent to ensure that the sheathing is suitable for large-scale production the stent, on the other hand, could not be derived from the prior art by a person skilled in the art, and were therefore not obvious.

Surprisingly, the object was achieved by the invention with the features of claim 1.

In an advantageous development, the axial shrinkage rate between the expanded state and the shrunk state can be less than 1.3: 1, preferably 1.10-1.03: 1. Due to the low axial shrinkage rate, sufficient coverage of the stent in the axial direction can be guaranteed with optimized material use.

It can also be advantageous if the inner diameter of the casing in the expanded state is approximately 10 to 20% larger than the outer diameter of the stent in the contracted state. In this way, the shrinkage rate of the sheathing can be optimally used and slipping of the sheathing in the shrunk state on the stent can be avoided.

In an advantageous development of the invention, the vascular support can be a metal lattice support. Such metal lattice supports have proven themselves in use as vascular supports. It usually consists of so-called memory metals, which can be deformed in a known manner by mechanical action and return to their original state by supplying heat, in order to thereby, for. B. to allow a radial enlargement of the stent.

It can also be advantageous if the casing is heated to more than 90 ° C., preferably approximately 100 ° C., in order to transfer the casing from its initial state into the expanded state. With simultaneous expansion of the jacket, the jacket can be gently transferred from its initial state to the expanded state.

It can be advantageous if the jacket is expanded by about 25% during the heating. This also ensures gentle material processing.

Furthermore, it can prove to be advantageous if the casing is cooled to approximately 20 ° to 25 ° C., preferably 23 ° C., after the expansion. When cooled, the sheathing is stabilized and can be pushed onto the stent.

It can prove to be advantageous if the jacket is heated to approximately 70 ° to 90 ° C., preferably approximately 80 ° C., in order to shrink it. In connection with the low shrinkage rate of the sheath, the supply of heat can be shortened, so that an unintentional expansion of the stent can be avoided when the sheath is pushed on.

It can prove to be advantageous if the heat is supplied for less than 40 seconds, preferably 30 seconds, during the transfer from the expanded state to the shrunk state. This also prevents an inadvertent expansion of the stent.

Furthermore, the invention relates to the use of a silicone-containing shrink tube with a shrink rate of less than 2: 1, preferably 1.1 to 1.2; 1, as a covering for a stent.

Furthermore, the invention relates to a stent with a silicone-containing, shrinkable casing, the shrinkage rate of the casing being less than 2: 1, preferably 1.1 to 1.2.

The mode of operation and functioning is explained in more detail below using an exemplary embodiment.

Show it: 1 shows the vascular support according to the invention with a sheath before assembly;

Fig. 2 shows the casing of Figure 1 with the stent attached.

FIG. 1 shows the vascular support 1 according to the invention. The vascular support 1 consists of a metal grid made of so-called memory metal. The stent is in a contracted state. By supplying heat, it is possible to bring the stent graft into a spread state. Since the stent consists of a memory metal, this expanded state is an initial state that the stent can assume again due to the supply of heat.

The casing 2 is essentially tubular and has an inner diameter which is approximately 10 to 20% larger than the outer diameter of the stent in the contracted state. This makes it possible to push the sheathing onto the stent.

The sheathing consists of a silicone-containing material with shrinkable properties. In the present example, the inner diameter of the shrink tube or inner diameter of the sheathing is 1.65 mm. The outer diameter of the stent in the contracted state is 1.4 mm and its inner diameter is 1.35 mm.

The sheathing consists of a shrinkable silicone formulation with a radial shrinking rate between 1.1 and 1.2: 1. The shrinking rate is calculated as the ratio between the outer diameter, in the expanded or expanded state of the sheathing, and the shrunk state of the Sheath if the sheath is not attached to a stent. If it is on the stent, it comes into contact with the stent when it is transferred from the expanded state to the shrunk state and rests against it under tension.

In the longitudinal direction of the stent, the shrinkage rate is 1.01 to 1.02: 1. Here the shrink rate is calculated as the ratio of the outer length of the jacket in the expanded state to the length of the sheathing in the shrunk state without vascular support. Overall, the length of the sheathing is dimensioned in such a way that covering of the stent is ensured in the expanded as well as in the shrunk state. In the shrunk state, the sheath contracts radially at the end faces of the stents, as shown in FIG. 2.

The implementation of the method according to the invention is explained below.

The stent is first brought into its contracted state in a known manner. The jacket is heated from its initial state to 100 ° C and expanded radially to 25%. It is then cooled to 23 ° C. so that the jacket is stabilized. It is now in its expanded or expanded state. The inside diameter is now approx. 1.65 mm. The axial shrinkage rate is approx. 1.01: 1 and the radial shrinkage rate is approx. 1: 2: 1. The metal lattice stent is then fixed on a mandrel and the expanded casing is pushed onto the stent. Next, the jacket is heated to 80 ° C for about 30 seconds, and the jacket shrinks. The dimensions of the stent and sheath are selected so that after the sheath has been warmed up and shrunk, the sheath rests on the stent under prestress.

Next, the stent with casing can now be inserted into a vessel and expanded.

Due to the given shrinkage rate of the casing, a vascular support can be provided with a casing in a simple and inexpensive manner. The low shrinkage rate also enables the tension increase in the sheath to be comparatively small. remains with the subsequent widening of the stent, so that a secure hold of the stent can be guaranteed in the vessel.

- claims -

Claims

claims

Method for applying an elastic, silicone-containing sheathing on a vascular support which can be converted from a contracted to a spread state by supplying heat, in which the casing is transferred from an initial state to a widened state and the sheathing and the vascular support are pushed into one another in the contracted state and then the sheathing is converted from its expanded state into a shrunk state by supplying energy, preferably heat, in that it lies at least in sections on the stent graft,

characterized,

that the sheathing is converted from its initial state to its expanded state by mechanical expansion with the supply of heat and cooled before the stent and sheathing are put together, and the shrinkage rate of the sheathing in the radial direction is less than 2: 1, preferably 1.1 to 1.2 : 1 is.

2. The method according to claim 1, characterized in that the axial shrinkage rate of the sheathing is less than 1.3: 1, preferably 1.01 to 1.02: 1.

3. The method according to claim 1 or 2, characterized in that the inner diameter of the casing in the expanded state is approximately 10 to 20% larger than the outer diameter of the stent in the contracted state.

4. The method according to any one of the preceding claims, characterized in that the stent is mounted on a mandrel for pushing together the stent and sheath.

5. The method according to any one of the preceding claims, characterized in that the stent is a metal lattice support.

6. The method according to any one of the preceding claims, characterized in that in order to transfer the casing from the initial state into the expanded state, the casing is heated to more than 90 ° C, preferably approximately 100 ° C.

7. The method according to any one of the preceding claims, characterized in that the casing is expanded by approximately 25% in the radial direction during the heating.

8. The method according to any one of the preceding claims, characterized in that after the expansion, the casing is cooled to approximately 20 ° to 25 ° C, preferably 23 ° C.

9. The method according to any one of the preceding claims, characterized in that for shrinking the sheathing, it is heated to about 70 ° to 90 ° C, preferably about 80 ° C.

10. The method according to any one of the preceding claims, characterized in that the heating is carried out for less than 40 seconds, preferably 30 seconds, while the jacket is shrinking.

11. Use of a silicone-containing shrink tube with a shrinkage rate of less than 2: 1, preferably 1.1 to 1.2: 1, as a covering for a stent.

12. Vascular support with a silicone-containing, shrinkable casing, the shrinkage rate of the casing being less than 2: 1, preferably 1.1 to 1.2.

Rehau, December 30, 2002 dr.we-zh-rb