Stent for transluminal implantation into hollow organs

The present invention relates to a stent for transluminal implantation in hollow organs, in particular in blood vessels, ureter. Esophagus or biliary ducts, having a substantially tubular body, which from a compressed state with a first cross-sectional diameter into an expanded state with an enlarged second cross-sectional diameter can be transferred, wherein the wall of the tubular body wiederholande both in longitudinal direction and in the circumferential direction of the stent, the having expansion ensuring border perforations.

A stent of this type is known from EP-A-0335341. The stent is composed of individual tubular elements, in their walls parallel to the longitudinal axis of the stent disposed apertures are formed. The individual elements are connected together by connecting portions, wherein in the walls of the connecting portions through holes are formed, each comprising a sloping and a parallel to the longitudinal axis of the stent disposed elongate portion and allow a tilting of the tubular elements against each other.

Another stent is disclosed in post-published EP-A-0,709,067 which forms a prior art according to Art. 54 (3) EPC, is known, this stent also has apertures that run parallel to the longitudinal axis of the stent and not oblique to the longitudinal axis of the have stents arranged sections.

Stents of the type mentioned are used for recanalization of diseased hollow organs. The stents are inserted in a compressed state via an insertion catheter to the site to be treated within the hollow organ, where they can be expanded by different measures to a diameter which corresponds to that of the healthy hollow organ so that a supporting effect of the hollow organ, for example, a vessel wall is achieved.

Depending is reached on how the expanded state, a distinction is made between ballonexpandierten stents and self-expanding stents. Ballonexpandierte stents are mounted on a special balloon catheter in a compressed state, up to the introduced site to be treated of the respective hollow body and there expanded by Balloninsufflation to the desired diameter by the plastic deformation of the stent material, the stent obtained in the expanded state its stability, so that a sufficient supporting effect of the hollow organ is achieved.

Self-expanding stents are held by auxiliaries, such as membrane-like coatings in its compressed state and inserted via a catheter to the site to be treated within the hollow organ. After removal of the coating these stents expand by their own power by itself to a predetermined diameter in the hollow organ so that the support of the wall of the hollow organ is achieved in this way. Basically, this self-expanding stent can be pushed down with the aid of a balloon catheter against the vessel wall.

The group of self-expanding stents include stents made of the so-called "memory metal" Nitinol. Nitinol is a nickel-titanium alloy with temperature-dependent shape behavior. For example, a nitinol wire imprinted a certain shape, and then the wire over a certain "memory temperature" heated so wins this wire is a "memory" of this form. On cooling then the thus treated wire back below its conversion temperature, which is dependent on the alloy and the heat treatment, it is soft and easily deformed. With a further heating above the conversion temperature of the wire automatically assumes the memorized shape again.

Self-expanding stents of the type mentioned, for example, be produced in that, parallel to its longitudinal axis extending slots are cut with a laser into the wall of a tubular body of small diameter. These slots are arranged circumferentially offset from each other so that upon expansion of the tubular body, for example by Balloninsufflation or by heating in the case of a stent of memory metal diamond-shaped openings occur also whose longitudinal axes extend parallel to the longitudinal axis of the tubular body.

However, stents of this type have the disadvantage that on the one hand both in compressed and the expanded state having low flexibility, so that on the one hand the insertion in curved hollow organs only to a limited extent possible and the other used in joint areas stent kinking tend , which can lead to reduction or interruption of blood flow in blood vessels or even to pierce the vessel wall.

Moreover, passes through the expansion of the stent to a shortening in the longitudinal direction, which is a relatively uncontrolled manner, so that the positioning of the stent may be at a specific site to be treated within the hollow organ relatively difficult.

The problem of the low flexibility is achieved at a known stent of this type in that the connection between individual adjacent in the longitudinal direction of the stent disposed diamonds is interrupted. A disadvantage of this arrangement, however, is that the free, sharp diamond ends, the outer curve radius protrude in particular at a bending of the stent, as occurs, for example when cornering implantation from the wall of the stent and protrude at the inner radius of curvature in the inner region of the stent. This has the result that injuries to the wall of the hollow organ and the balloon of a balloon catheter used can occur. These are complications that can not be tolerated in practice.

The present invention has for its object to provide a stent of the type mentioned, having firstly both the compressed and the expanded state, a high degree of flexibility, while providing a safe, risk-free application is ensured and in which the expansion of shortening occurs, so that a proper positioning of the stent is achieved.

This object is solved starting from a stent of the aforementioned type by the characterizing features of claim 1 according to the invention.

Surprisingly, can be significantly improved by the oblique arrangement of the perforations, the flexibility of the stent in both the compressed and the expanded state relative to a stent having parallel to its longitudinal axis extending in the compressed state perforations. As can thus be dispensed with the severing of the links between longitudinally juxtaposed lozenges, exist in an inventively embodied stent no sharp edges, the violations of the wall of the hollow organ or a balloon of a balloon catheter could cause.

Furthermore is achieved by the oblique arrangement of the perforations that a shortening trend in expansion of the stent can be counteracted. For example, in the preparation of a self-expanding stents made of memory metal it expands from its compressed state by threading an expansion axis, said first and usual shortening occurs. The diameter of the expansion shaft is in this case selected to be equal to the desired diameter of the stent in the expanded state.

Subsequently, the drawn onto the stent expansion axis in the longitudinal direction is stretched as far until the desired length is reached, reduces the angle of inclination of part of the inclined portions of the perforations. The stent is heated, the memory temperature in this state, the upper, he takes after cooling below the conversion temperature and then reheating in turn to this form, in which the shortening is compensated. Usually corresponds to the desired length of the length of the stent in the compressed state in order to achieve an exact positioning of the expanded stent during insertion.

According to an advantageous embodiment of the invention the openings form in the wall of the tubular body slot-like openings in the compressed state of the stent. In this way, a particularly simple production of the inventively designed stent is possible since the slot-shaped openings can be cut, for example by a laser in the tubular body. However, in principle it is also possible that the recesses are formed already in the compressed state broader, which can be achieved for example by punching or Erodiervorgänge.

The openings may be created in both the compressed and the expanded state of the stent. The production in the compressed state is advantageous, however, since the generation of the slot-shaped openings, the material losses are smaller than in the generation of corresponding expanded openings.

According to a further advantageous embodiment, the slot-shaped openings on several, in particular three sections which are zigzag-shaped and are each arranged at an angle to the longitudinal axis of the stent. This particularly uniform bending properties of the stent can be achieved both in the compressed and the expanded state.

The lying between the perforations of the wall material of the tubular body forms boundary elements for the apertures which are expandable to the expansion of the stent. The facing ends of longitudinally arranged adjacent border elements via in particular V-shaped intermediate elements are connected. Through this design a more flexible design of an inventively designed stent is achieved on the one hand. Secondly, due to the provision of separate intermediate elements, a decoupling between the boundary elements, which ensure the expansion of the stent in the first place, and the intermediate elements, which are preferably used for shortening compensation achieved.

Further advantageous embodiments of the invention are specified in the subclaims.

In the following the invention using an exemplary embodiment is described with reference to the drawings in greater detail; in which:<dl id="dl0001"><dt>Fig. 1</dt><dd>a truncated, flat pattern shown to produce the perforations for a stent according to the invention,</dd><dt>FIG. 2</dt><dd>a detailed view of FIG. 1,</dd><dt>Fig. 3</dt><dd>the detailed view of FIG. 2 as well as a corresponding detailed view in an inventively embodied stent in the expanded state,</dd><dt>Fig. 4</dt><dd>a further detail view of an inventively embodied stent in radial and tangential direction and</dd><dt>Fig. 5</dt><dd>a schematic cross section through an inventively designed stent.</dd></dl>

Fig. 1 (see FIG. 5) shows a cut pattern, as for example by means of a laser into the wall of a tubular body 1 is cut for producing a stent formed according to the invention. To clarify the position of the sections within the wall of the tubular body 1, the course of the longitudinal axis of the tubular body 1 is provided with the reference numeral 2 in Fig. 1.

By the cutting operation are formed in the wall of the tubular body 1 through apertures 3, 4, which have the form of that shown in Fig. 1 slot-shaped openings in the compressed state.

The slit-shaped openings 3 have three sections 3 ', 3 "and 3"', which are each arranged at an angle to the longitudinal axis 2 of the tubular body 1 and together form in each case Z-shaped slit-shaped openings 3rd

The lying between the perforations 3 material of the wall of the tubular body 1 forms each Umrandurtgselemente 5, which, as seen particularly clearly in Fig. 3b, each represent boundaries of the perforations 3.

The apertures 3 are point-symmetrical with respect to points of symmetry 6, which are together with the respective ends 7, 8 of the apertures 3 on parallels to the longitudinal axis 2 of the tubular body. 1 The symmetry point 6 is at the center between the two ends 7, 8 of the perforations arranged 3rd

Each two adjacent in the circumferential direction of the tubular body 1 arranged (superposed in FIG. 1) border elements 5 are connected via connection points 10 with each other, which are each arranged between the points of symmetry 6 of the boundary elements 5.

The mutually facing ends 11, 12 of two in the longitudinal direction of adjacently disposed boundary elements 5 are connected to each other via V-shaped intermediate elements. 13 The legs 14, 15 of the intermediate elements 13 are each arranged at an angle to the longitudinal axis 2 of the tubular body. 1

The generated by the pattern shown in FIG. 1 through holes 3, 4 are uniformly distributed over the entire circumference of the tubular body 1, so that for example the outline elements shown in Fig. 1 5 'and 5' 'coincide.

Depending on the length of the tubular body 1 more or less V-shaped intermediate elements 13 and boundary elements 5 can be distributed along the longitudinal axis 2 of the tubular body 1 as in Fig. 1 are shown. Accordingly, depending on the size of the tubular body 1, the number of V-shaped intermediate elements 13 and of the border elements 5 along the circumference of the tubular body 1 may vary.

From Fig. 2, the point-symmetrical construction of the slit-shaped openings 3 and thus the boundary elements 5 is particularly clearly visible. In particular, the advantages of a stent according to the invention are achieved in that the marked longitudinally with a and a 'respectively in the circumferential direction of the tubular body 1 with b and b' geometric distances are equal respectively.

In Fig. 3 it can be seen how the width of the border element 5 is increased by widening the opening 3 in the circumferential direction of the tubular body 1, whereby an expansion of the tubular body 1 is achieved. Furthermore, Fig. 3 it is apparent that the apparent longitudinal shortening of the border element 5, which is recognized by the fact that the end 11 of the border is 5 moved in Fig. 3b from the position in Fig. 3a to the left, by a simultaneous expansion of V -shaped intermediate member 13 is balanced so that the positions of the end 12 of the adjacently arranged boundary element 5 in the compressed (Fig. 3a) and in the expanded (Fig. 3b) consistent state. In this way, each having a unit of border element 5 and intermediate element 13 - and thus also the tubular body 1 as a whole - in the compressed state the same length as in the expanded state.

adjacent the region of the joints 10 between two in the circumferential direction of the tubular body 1 arranged frame members 5 are provided recesses 16, so that at these locations the bending of the boundary elements 5 is facilitated. Thereby, the elastic properties of a stent according to the invention be further improved.

In Fig. 4, the recesses 16 shown in detail how they can be provided for example between two directly interconnected boundary elements 5. Corresponding recesses 16 can also be provided between the boundary elements 5 and the V-shaped intermediate elements. 13 Here, both the recesses in the circumferential direction, as shown in Fig. 4a, and recesses in the radial direction, as shown in Fig. 4b, as well as any other type of recesses possible that affect the flexibility of the inventive design stents low.

In the FIG. 5 cross section schematically shown an inventively embodied stent 1 the perforations 3 are merely indicated by oblique strokes 19th The tubular body 1 has at its two ends extending in the peripheral direction than the projections 17 formed on thickened portions, which extend radially outward. Between the projections 17, an elastic shroud 18 is provided whose radial thickness equal to the radial dimensions of the projecting parts of the projections 17 is substantially, so that the stent has a substantially uniform outer surface. Furthermore, 5 seen from Fig., That the inner surface of the tubular body 1 is formed to extend uniformly.

The inventively constructed stent is preferably prepared as follows, prepared and used:

In the wall of an existing of memory metal tubular body 1 can be cut with a laser, the cut pattern shown in Fig. 1 and so that the slit-shaped openings 3, 4. The diameter of the tubular body 1 is selected such that it corresponds to the required for implanting the compressed state of the stent.

After the pattern shown in FIG. 1 has been cut over the entire length and the entire circumference of the tubular body 1, the tubular body 1 is drawn onto an expansion axis, their diameter, the required in the inserted expanded state diameter of the stent corresponds. Characterized the slot-shaped openings are extended 3 and 4, as shown in Fig. 3b. Subsequently, the drawn onto the axis of expansion tubular body as far as stretched in the longitudinal direction until the occurring by the expansion shortening is compensated by bending of the V-shaped intermediate elements 13, so that a surface structure of boundary elements 5 and intermediate elements 13 is created, as shown in Fig. 3b are shown.

By heating the tubular body on the memory temperature which arose end mold is then stored in the material.

After cooling the stent below the conversion temperature of the stent can again to its the compressed state corresponding output diameter will be pressed together and with a resilient sheath 18, which consists for example of nylon (registered trademark), polyethylene, polyamide or polyurethane elastomers, are coated. By the projections 17 a provided diches stripping the elastic sleeve 18 during implantation is prevented. At the same time 17, the stent can be better observed at the onset on the X-ray screen by the projections, so that proper positioning of the stent is guaranteed at the desired location within the hollow organ.

The stent is positioned about a delivery catheter at the desired location, wherein an expansion of the stent is prevented, for example, by an additional wrapping or a special catheter. By stripping the sheath or the catheter, the tubular body 1 due to the increases lying above the conversion temperature to body temperature, its memorized shape. In this case, due to the shortening of the compensation achieved by the intermediate elements 13, the length in the expanded state with the length of the stent in the compressed state is consistent, so that the observed on the X-ray screen during insertion position of both ends of the stent is maintained.

Due to the inventive structure of the tubular body 1 a high degree of flexibility is achieved in both the compressed and the expanded state, so that both an implantation in curved hollow organs as well as arranged in the region of joints hollow organs is possible. A bending of the stent by bending the joints is largely ruled by the erzieke flexibility. In addition, it is ensured by the inventive design structure both in the compressed and the expanded state, a good longitudinal and transverse stability of the stent.

Furthermore, both the outside and the inside of the tubular body are evenly distributed and have in particular no sharp outward or inward protruding elements so that neither injuries the hollow organ nor a possible expansion supportive balloon of a balloon catheter may occur.

Apart from the described embodiment of memory metal can take advantage of an inventively embodied stents even when using other materials, such as tantalum. Stainless steel or biocompatible plastics such as polyethylene, polyamide or polyurethane elastomers are obtained.