U.S. patent application number 12/057806 was filed with the patent office on 2008-10-02 for stent having radially expandable main body.
This patent application is currently assigned to BIOTRONIK VI PATENT AG. Invention is credited to Daniel Lootz, Johannes Riedmueller, Bettina Surber, Daniel Wintsch.
Application Number | 20080243230 12/057806 |
Document ID | / |
Family ID | 39456395 |
Filed Date | 2008-10-02 |
United States Patent
Application |
20080243230 |
Kind Code |
A1 |
Lootz; Daniel ; et
al. |
October 2, 2008 |
STENT HAVING RADIALLY EXPANDABLE MAIN BODY
Abstract
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.
Inventors: |
Lootz; Daniel; (Rostock,
DE) ; Surber; Bettina; (Duebendorf, CH) ;
Wintsch; Daniel; (Zurich, CH) ; Riedmueller;
Johannes; (Nuernberg, DE) |
Correspondence
Address: |
POWELL GOLDSTEIN LLP
ONE ATLANTIC CENTER FOURTEENTH FLOOR, 1201 WEST PEACHTREE STREET NW
ATLANTA
GA
30309-3488
US
|
Assignee: |
BIOTRONIK VI PATENT AG
Baar
CH
|
Family ID: |
39456395 |
Appl. No.: |
12/057806 |
Filed: |
March 28, 2008 |
Current U.S.
Class: |
623/1.15 ;
623/1.34 |
Current CPC
Class: |
A61F 2002/91591
20130101; A61F 2002/9505 20130101; A61F 2230/0013 20130101; A61F
2002/91533 20130101; A61F 2/958 20130101; A61F 2250/0098 20130101;
A61F 2002/91575 20130101; A61F 2/91 20130101; A61F 2250/0071
20130101; A61F 2/915 20130101 |
Class at
Publication: |
623/1.15 ;
623/1.34 |
International
Class: |
A61F 2/82 20060101
A61F002/82 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 31, 2007 |
DE |
10 2007 015 670.9 |
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.
Description
PRIORITY CLAIM
[0001] 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.
FIELD
[0002] The present disclosure relates to expandable vascular
stents.
BACKGROUND
[0003] One 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.
[0004] 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.
[0005] 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.
[0006] 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.
SUMMARY
[0007] The present disclosure describes several exemplary
embodiments of the present invention.
[0008] 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.
[0009] 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.
[0010] 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.
[0011] 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.
[0012] 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.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] Various aspects of the present disclosure are described
hereinbelow with reference to the accompanying figures.
[0014] FIG. 1 is a perspective view of one exemplary embodiment of
a stent in its contracted starting position having a terminal glued
joint as the stabilization means;
[0015] FIG. 2 is a detail top view of the stent in an unwound view
having a glued joint variant;
[0016] FIG. 3 is a detail top view of the stent in an unwound view
having a different glued joint variant;
[0017] FIG. 4 is a schematic detail excerpt in an unwound
illustration of the stent having catches as the stabilization
means;
[0018] FIG. 5 is a schematic detail excerpt in an unwound view of a
stent having a boundary fixing traverse;
[0019] FIG. 6 is a schematic detail excerpt in an unwound view of
an exemplary embodiment of a stent having a different boundary
fixing traverse;
[0020] FIG. 7 is a schematic detail view in an unwound view of an
exemplary embodiment of a stent having boundary fine structure
struts as the stabilization means;
[0021] FIG. 8 is an enlarged detail excerpt as shown in FIG. 7;
[0022] FIG. 9 is a perspective partial illustration of an exemplary
embodiment of a stent having extension struts for removable
fastening to a balloon catheter;
[0023] FIG. 10 is a top view of the stent as shown in FIG. 9 in an
unwound view;
[0024] FIG. 11 is a detail top view of an exemplary embodiment of a
stent in an unwound view having marker projections coupled to one
another; and
[0025] FIG. 12 is a detail top view of an exemplary embodiment of a
stent in an online view having marker projections coupled in a
ring.
DETAILED DESCRIPTION
[0026] FIG. 1 clarifies the structure of the stent in its
contracted starting position. The stent is worked out of a
cylindrical metal body by laser cutting in such a manner that the
stent has multiple support segments 1 running around the
circumference U and arrayed in the axial direction A on one
another, which are each formed by one of the struts 2 meandering in
their coarse structure in the contracted starting position
shown.
[0027] 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.
[0028] 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.
[0029] To achieve the additional radial fixing of the stent desired
according to the present disclosure, in the variants shown in FIGS.
1-3, a glued joint 6 is provided which may be applied between the
two terminal meandering curves 3 on diametrically opposite radial
positions in the form of a grouting point, for example. This glued
joint 6 is shown schematically in FIG. 2. With this type of glued
joint 6, the adhesive faces are loaded by tension.
[0030] 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 FIG. 3.
[0031] The individual points of the glued joint 6 may not only be
situated terminally, as shown in FIGS. 1-3, but also distributed on
the circumference over the length of the stent 1. With such
multiple positioning, upon radial expansion of the stent, the
fixing is detached automatically in chronological sequence in
accordance with the retention force. Experiments have shown that in
spite of asymmetrical detachment of the individual fixed points,
the stent may be open homogeneously if the fixing force is only
large enough that the axial connectors 4 are still capable of
absorbing it. If glued joints 6' are positioned in the area of the
particular strut 2 second from the outside, for example, the axial
connectors 4 may also act on the glued joint 6' from both sides
which favors homogeneous opening behavior. In this case, the
outermost strut 2 is either to be as short as possible or have the
fine structures described in greater detail on the basis of FIGS. 7
and 8 on the edge to suppress flaring.
[0032] FIG. 4 shows a further exemplary embodiment for the
stabilization means for additional radial fixing of the stent. Two
neighboring meandering curves 3 of a strut 2 are coupled to one
another in the contracted starting position at their edges by
hooked catch elements 7, 8. When the stent is transferred into its
contracted starting position, the so-called crimping, the catch
elements 7, 8 are engaged with one another. The stent is thus held
together at its edge, so that the "flaring" cited hereinabove is
avoided. During the radial expansion, the engagement between
elements 7, 8 is broken open and the stent may open
homogeneously.
[0033] 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 FIG.
4. This fixing is also produced during crimping by hooking of the
projections 9, 10 and broken upon expansion of the stent. It is
recognizable that the hooked projections 9, 10 may be provided on
arbitrary struts 2 along the stent.
[0034] FIGS. 5 and 6 show further exemplary embodiments of the
stabilization means for the additional radial fixing of the stent
in the cramped state. In these embodiments, fixing traverses 11
shaped in one piece on the boundary struts 2 are provided which
connect to the adjacent meandering curves 3 of a strut 2 from
zenith point 5 to zenith point 5. While only one fixing traverse 11
is provided in FIG. 5, in the exemplary embodiment shown in FIG. 6,
the boundary of the stent is completely terminated by a row of
fixing traverses 11.
[0035] 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.
[0036] A further exemplary embodiment of the stabilization means
provided according to the present disclosure is shown in FIGS. 7
and 8. These are peripheral fine structure struts 14 on the
boundary at the ends 13 of the stent, which are bound to the
exterior sides 15 of the meandering curves 3. These fine structure
struts 14 are formed in each case by two struts 16, 17 running
essentially parallel having coupling struts 18 running in the axial
direction. The basic configuration of the fine structure struts 14
is thus ladder-like, the double struts 16, 17 being folded in a
zigzag in the lateral plane of the stent. Curved groin points 19
are shaped into the double struts 16, 17 in the bend points, via
which the coupling struts 18 may be fastened in one piece while
protecting the material in regard to the radial expansion of the
fine structure struts 14 at the struts 16, 17. The expandability of
the fine structure struts 14 is improved by the curved shape in
these groin points 19.
[0037] As schematically indicated in FIG. 8, the fine structure
struts 14 in the area of the interior groin points 19, which are
adjacent to one another in the contracted starting position, are
additionally fixed by a glued joint 6 or also catch means (not
shown here), for example. The entire stent is thus stabilized on
its front-side boundary in the crimped configuration in such a
manner that flaring is kept as small as possible. Due to the fixing
at the interior groin points 19, the opening forces act on both
sides of this fixing, so that higher fixing forces may be overcome
without impermissibly distorting the stent structure.
[0038] A further exemplary embodiment of the stabilization means
for additional radial fixing of the stent is illustrated in FIGS. 9
and 10. These are extension struts 20, which run essentially in the
axial direction A and are bound to the strut at one end via an
intended breakpoint 21 to the external strut 2. The free end 22 of
the extension struts 20 is permanently fastened in each case in a
suitable maimer to a balloon catheter 23, only schematically
indicated in FIG. 9.
[0039] 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.
[0040] Exemplary embodiments for stabilization means against
flaring shown in FIGS. 11 and 12 use the x-ray marker projections
24 often present in stents, which are formed as eye-shaped
projections onto the meandering curves 3 of the external struts 2
and are provided with a thermoplastically moldable marker polymer
coating 25. To use these elements, which are known in stents, as
stabilization means against flaring, the x-ray marker projections
24 having their marker polymer coating 25 are designed in such a
manner that the x-ray marker projections 24 contact one another
after the crimping of the stent and are reshaped into a peripheral
ring by a thermal treatment of the marker polymer coating 25. The
ring formation is supported by transverse connection elements 26
protruding in the peripheral direction from the x-ray marker
projections 24, which may be designed as either I-shaped or
T-shaped in a top view.
[0041] Finally, it is still possible, as shown in FIG. 12, to equip
stents with polymer-coated x-ray marking projections 24 against
flaring in such a manner that a peripheral ring made of magnesium,
for example, is pushed onto the projections 24 having their coating
25 which is embedded therein by heating and brief melting of the
marker polymer coating 25 and thus fixed. The ring 27 may comprise
rigid material or wire, and may also be laid on only a partial
circumferential length around the stent.
[0042] All patents, patent applications and publications referred
to herein are incorporated by reference in their entirety.
* * * * *