FIELD OF THE INVENTION
The present invention relates to a coronary stent comprising a tubular, flexbile body whose wall has a web structure, 5 said web structure comprising a plurality of adjacent cells which are denned by webs and which are each connected via joint webs to adjacent cells.
BACKGROUND OF THE INVENTION 10
Very different types of coronary stents are already known from the prior art. The stents form a vascular prosthesis made from a physically compatible material. The stent or stent prosthesis is used for expanding blood vessels or also other body orifices and for keeping said vessels in their expanded state. To this end, the stent is positioned in a patient's body in its non-expanded state and is then expanded by suitable means, for instance a balloon catheter. During expansion the individual web portions of the stent 2Q are deformed such that the stent permanently remains in its expanded form.
A stent of such a type is, for instance, shown in Utility Model 297 02 671.
When stents are constructed, the fundamental problem 25 arises that these must have a sufficiently small diameter in their non-expanded state to be introducible into and positionable in a patient's body. The stents must be flexible along their longitudinal axis to some degree so as to be able to follow the shapes of, for instance, blood vessels. During 30 expansion the stent must be expanded such that its outer diameter becomes considerably larger. Such an expansion is achieved by deforming the individual web portions in such a manner that no cracks, or the like, are formed.
SUMMARY OF THE INVENTION
It is the object of the present invention to provide a stent of the above-mentioned type which is expandable and, nevertheless, of a simple structure, which can easily be manufactured and safely used. 40
This object is achieved according to the invention by.
Hence, according to the invention, first and second cells that are movable away from one another are alternately
arranged in the axial direction of the stent, identical cells are „ & 45 respectively provided in neighboring fashion in the circumferential direction, in the non-expanded state of the stent the first cells are provided at two opposite sides with folded webs and, in the non-expanded state, the second cells are provided at all sides with web portions that are folded and/or 5Q placed together.
The stent of the invention is characterized by several considerable advantages.
In the non-expanded state the alternating arrangement of different cells yields sufficient strength on the one hand and 55 sufficient flexibility on the other hand. Since the webs or web portions of the different cells have different expansion characteristics, the stent can be expanded in a simple and reliable manner. Hence, the different cells permit a corresponding deformation of the webs, so that the formation of go cracks or the like can be ruled out.
It has turned out to be particularly advantageous when the folded webs of the first cells have a zig-zag-shaped design, so that these preferably form a tape-like portion extending in circumferential direction. These tape-like portions increase 65 the strength of the stent and also ensure the dimensional stability thereof in the expanded state.
Since the webs or web portions of the second cells have a different design, different expansion characteristics of the webs or web portions are possible. While the zig-zag-shaped web portions are deformable in a manner similar to that of the first cells, the web portions which are placed together in arc-shaped configuration permit a high degree of deformation and expansion. Very long web portions can be provided in a space-saving manner in the non-expanded state owing to the preferably s-shaped arrangement.
The non-folded webs of the first cells are preferably arranged in arc-shaped configuration and parallel to one another, which also leads to a sufficient degree of deformability of the cells and to an increase in stability, in particular in the expanded state.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention shall now be described with reference to an embodiment in conjunction with the drawing, in which:
FIG. 1 is a schematically very simplified illustration of the basic structure of the stent according to the invention;
FIG. 2 is an illustration of the web structure of the wall of the stent in the non-expanded state;
FIG. 3 is an enlarged illustration of a first cell, and
FIG. 4 is an enlarged illustration of a second cell.
FIG. 1 shows the fundamental structure of an inventive stent 1 which comprises a flexible, tubular body 2 having a wall 3, of which the front side is visible in FIG. 1.
FIG. 2 shows the construction of the web structure of the invention.
DETAILED DESCRIPTION OF THE
As becomes apparent from the figures, rows of first cells
4 and of adjoining second cells 5 are alternately provided in circumferential direction. Each of the first cells 4 are provided at two opposite sides with webs 6 that are arrranged in zig-zag-shaped or v-shaped configuration, while the other sides of the first cells 4 are formed by arc-shaped webs 9 that are parallel to one another.
Shape and design of the second cells 5 differ from those of the first cells 4 by the feature that all webs that define cells
5 are folded or placed together.
As follows from FIG. 4, v-shaped or zig-zag-shaped webs
6 are formed at two opposite sides of the cell 5, while the two other opposite portions have provided thereat webs 8 which are in arc-shaped engagement. Thus, the webs 8 have an s-shaped structure.
Accordingly, as best seen in FIGS. 2-4, coronary stent 1 has a plurality of first cells 4 arranged to form a plurality of first circumferential rows that are axially spaced apart. A plurality of first and second circumferential webs 6 and a plurality of first and second axial webs 9 form the first cells 4. The axial webs 9 are connected to the circumferential webs 6 such that the circumferentially adjacent ones of the first cells 4 share one of the axial webs 9. The first cells 4 have different expansion characteristics from second cells 5. The plurality of second cells 5 are arranged to form a plurality of second circumferential rows that are axially spaced apart and located between the first circumferential rows of first cells 4. Thus, the adjacent second circumferential rows alternate in an axial direction of the tubular coronary stent as seen in FIG. 2. The first and second circumferential webs 6 and third and fourth axial webs 8 form the second cells. The third and fourth axial webs 8 are