STENT HAVING RADIALLY EXPANDABLE MAIN BODY
A stent made of a material having a low strength and having a main body circumscribing a cylindrical shape and radially expandable from a contracted starting position into a dilated support position, comprising a) a plurality of support segments disposed around the circumference and arrayed on one another in the axial direction each segment being formed by a strut meandering in its coarse structure in its contracted starting position and having alternately opposing meandering curves expandable into the support position made of flexible material; b) a plurality of axial connectors connecting between zenith points of at least a part of the meandering curves in the axial-parallel direction of the support segments; and c) at least one means for stabilizing the strut coarse structure in its contracted starting position against radial expansion and being automatically detachable upon a radial expansion of the stent.
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This patent application claims priority to German Patent Application No. 10 2007 015 670.9, filed Mar. 31, 2007, the disclosure of which is incorporated herein by reference in its entirety.
FIELDThe present disclosure relates to expandable vascular stents.
BACKGROUNDOne example of a vascular implant is described in detail in International Patent Publication No. WO 2004/103 215 A1, in particular, in regard to the fundamental areas of application of such stents and the special problems upon use of materials having a low ductile yield and also lower strengths, such as magnesium alloys.
In the embodiment which may be inferred from this publication, the stent is implemented by a main body circumscribed by a cylindrical shape and radially expandable from a contracted starting position into a dilated support position which, on one hand, comprises multiple support segments running around the circumference and arrayed in the axial direction on one another. The support segments are each formed by a strut which is meandering in coarse structure in its contracted starting position having alternating opposing meandering curves made of flexible material. On the other hand, the main body has axial connectors running in the axial-parallel direction which connect the support segments between zenith points of at least a part of the meandering curves.
The above-mentioned magnesium alloys as the material for producing stents have significantly lower strength values than typical construction materials for balloon-expandable stents, such as medical steel having the material identifications 316L, MP35N or L 605. These lower strength values cause problems in the practical application of the stents. It is thus necessary for the stent placement to mount the stent on a balloon catheter. For this purpose, the stent, which is structured from a sleeve material by laser cutting, for example, is crimped onto the balloon catheter in its contracted starting position. The stent is also guided on the catheter system through curved areas of the insertion or blood vessel system in this state during the implantation. Individual struts of the stent may open in the corresponding passages, by which the retention forces of the stent on the catheter are reduced. This causes a significant risk of loss of the stent.
Especially endangered areas of the stent are the terminal strut elements having their meandering curves. In addition, the danger arises due to projecting edge segments, the so-called “flaring,” that, in addition to the mechanical irritation of the internal vascular wall upon passage of the stenosis or the retraction into the insertion catheter, unintended stripping of the stent from the balloon catheter will occur.
SUMMARYThe present disclosure describes several exemplary embodiments of the present invention.
One aspect of the present disclosure provides a stent made of a material having a low strength and having a main body circumscribing a cylindrical shape and radially expandable from a contracted starting position into a dilated support position, comprising a) a plurality of support segments disposed around the circumference and arrayed on one another in the axial direction, each segment being formed by a strut meandering in its coarse structure in its contracted starting position and having alternately opposing meandering curves expandable into the support position made of flexible material; and b) a plurality of axial connectors connecting between zenith points of at least a part of the meandering curves in the axial-parallel direction of the support segments; and c) at least one means for stabilizing the strut coarse structure in its contracted starting position against radial expansion and being automatically detachable upon a radial expansion of the stent.
One feature of the present disclosure provides a stent of the type according to the species in such a manner that unintended expansion of the entire stent or exposed areas thereof, such as the terminal front edges, is reliably prevented during the implantation.
This feature is achieved according to the present disclosure by a means for stabilizing the strut coarse structure in its contracted starting position against radial expansion which are integrated in the stent design. These stabilization means are then detachable automatically upon the actual radial expansion of the stent.
These stabilization means advantageously secure radial locking of the stent in its crimped state so that unintended expansion of the stent, even in partial areas, is avoided because of this fixing.
According to preferred embodiments of the present disclosure, these stabilization means may be implemented in different ways, for example, by detachable glued joints between adjacent meandering curves of a strut or from strut to strut, by catch elements in the stent structure, boundary fixing traverses or by fine structure struts against the cited “flaring.” More detailed explanations may be inferred from the following description, in which exemplary embodiments of the subject matter of the present disclosure are explained in greater detail on the basis of the attached drawings.
Various aspects of the present disclosure are described hereinbelow with reference to the accompanying figures.
In the direction parallel to the axial direction A, the support segments 1 are connected to one another by axial connectors 4, which each run between the zenith points 5 of meandering curves 3 to be connected. The axial connectors 4 always run from the exterior side of a meandering curve 3 to the interior side of the meandering curve 3 of the adjacent strut due to the offset of the adjacent support segments 1 around the circumference U.
As is not shown in greater detail in the drawings, upon radial expansion of the stent, the sections of the meandering curves 3 running between the zenith points 5 are deployed around the circumference U. The closer the corresponding sections approach to the circumference U, the greater the so-called collapsing pressure of the stent.
To achieve the additional radial fixing of the stent desired according to the present disclosure, in the variants shown in
In another exemplary embodiment, it is also possible to attach the glued joint 6 in such a manner that the adhesive faces are loaded by shear, as indicated in
The individual points of the glued joint 6 may not only be situated terminally, as shown in
In a further exemplary embodiment, the configuration of catch elements in the form of hooked projections 9, 10 in the interior of a meandering curve 3 is shown by dashed lines in
Each fixing traverse 11 has a double-arched course having a central bend 12 which acts as the intended breakpoint upon radial expansion of the stent. The stent, as already described in connection with the glued joint 6, may expand homogeneously by the tearing of the fixing traverses 11.
A further exemplary embodiment of the stabilization means provided according to the present disclosure is shown in
As schematically indicated in
A further exemplary embodiment of the stabilization means for additional radial fixing of the stent is illustrated in
The extension struts 21 again counteract a radial expansion of the meandering curves 3 of the external struts 2, in particular, which suppresses flaring. Upon dilation of the stent, the intended breakpoints 21 are torn and the stent is thus released from the extension struts 20.
Exemplary embodiments for stabilization means against flaring shown in
Finally, it is still possible, as shown in
All patents, patent applications and publications referred to herein are incorporated by reference in their entirety.
Claims
1. A stent made of a material having a low strength and having a main body circumscribing a cylindrical shape and radially expandable from a contracted starting position into a dilated support position, comprising:
- a) a plurality of support segments disposed around the circumference and arrayed on one another in the axial direction each segment being formed by a strut meandering in its coarse structure in its contracted starting position and having alternately opposing meandering curves expandable into the support position made of flexible material;
- b) a plurality of axial connectors connecting between zenith points of at least a part of the meandering curves in the axial-parallel direction of the support segments; and
- c) at least one means for stabilizing the strut coarse structure in its contracted starting position against radial expansion and being automatically detachable upon a radial expansion of the stent.
2. The stent of claim 1, wherein the at least one stabilization means is formed by a detachable glued joint between adjacent meandering curves of one or more struts.
3. The stent of claim 2, wherein the glued joint is attached to boundary and internal struts.
4. The stent of claim 2, wherein the glued joint is attached in such a manner that the glued joint may be loaded upon radial expansion by tension or shear.
5. The stent of claim 1, wherein the at least one stabilization means is formed by catch elements which interact with one another on the meandering curves which may be engaged with one another upon transfer of the stent into its contracted starting position and are detachable upon radial expansion of the stent.
6. The stent of claim 5, wherein the catch elements are formed by hook projections on the meandering curves.
7. The stent of claim 1, wherein the at least one stabilization means is formed by fixing traverses which connect the boundary meandering curves and may be broken open upon radial expansion.
8. The stent of claim 7, wherein the fixing traverses run between zenith points of two adjacent meandering curves and have a bend as the intended breakpoint.
9. The stent of claim 1, wherein the at least one stabilization means is formed by a plurality of fine structure struts peripherally disposed around the boundary of the stent ends.
10. The stent of claim 9, wherein the plurality of fine structure struts are implemented as double struts folded in a zigzag in a lateral plane of the stent which are fixed on one another at their adjacent groin points in the contracted starting position.
11. The stent of claim 1, wherein the at least one stabilization means is formed by a plurality of extension struts on the stent which detachably connect the boundary struts to the catheter for placing the stent.
12. The stent of claim 11, wherein the plurality of extension struts are each bonded to the stent via an intended breakpoint.
13. The stent of claim 1, further comprising a plurality of x-ray marker projections coated via marker polymer on the boundary struts, wherein the at least one stabilization means is formed by x-ray marker projections coupled in a ring via the marker polymer coating in the contracted state.
14. The stent of claim 13, wherein the plurality of x-ray marker projections are provided with radially oriented transverse connection elements.
15. The stent of claim 13, wherein a ring which is embedded in the marker polymer coating is drawn onto the x-ray marker projections in the contracted stent state.
Type: Application
Filed: Mar 28, 2008
Publication Date: Oct 2, 2008
Applicant: BIOTRONIK VI PATENT AG (Baar)
Inventors: Daniel Lootz (Rostock), Bettina Surber (Duebendorf), Daniel Wintsch (Zurich), Johannes Riedmueller (Nuernberg)
Application Number: 12/057,806
International Classification: A61F 2/82 (20060101);