U.S. patent application number 09/983837 was filed with the patent office on 2002-05-02 for stent having a multiplicity of undulating longitudinals.
Invention is credited to Fischell, David R., Fischell, Robert E., Fischell, Tim A..
Application Number | 20020052646 09/983837 |
Document ID | / |
Family ID | 22748604 |
Filed Date | 2002-05-02 |
United States Patent
Application |
20020052646 |
Kind Code |
A1 |
Fischell, Robert E. ; et
al. |
May 2, 2002 |
Stent having a multiplicity of undulating longitudinals
Abstract
A stent which is adapted for placement in the vessels of a human
body is provided. The stent may be in the form of a thin-walled
metal cylinder having a longitudinal axis. The stent has a proximal
end and a distal end and includes a number of circumferentially
relatively rigid portions. The relatively rigid portions are joined
to each other by one or more longitudinals which extend in a
substantially longitudinal direction. At least a portion of at
least one of the longitudinals has an undulating shape where a
first relatively rigid portion is located at the proximal end of
the stent and a second relatively rigid portion is located at the
distal end of the stent.
Inventors: |
Fischell, Robert E.;
(Dayton, MD) ; Fischell, David R.; (Fair Haven,
NJ) ; Fischell, Tim A.; (Nashville, TN) |
Correspondence
Address: |
ROSENBERG, KLEIN & LEE
3458 ELLICOTT CENTER DRIVE-SUITE 101
ELLICOTT CITY
MD
21043
US
|
Family ID: |
22748604 |
Appl. No.: |
09/983837 |
Filed: |
October 26, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09983837 |
Oct 26, 2001 |
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09596074 |
Jun 16, 2000 |
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09596074 |
Jun 16, 2000 |
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09263518 |
Mar 5, 1999 |
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09263518 |
Mar 5, 1999 |
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08864221 |
May 28, 1997 |
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08864221 |
May 28, 1997 |
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08202128 |
Feb 25, 1994 |
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Current U.S.
Class: |
623/1.15 |
Current CPC
Class: |
A61F 2210/0019 20130101;
A61F 2002/825 20130101; A61F 2/90 20130101; A61F 2002/91533
20130101; A61F 2/91 20130101; A61F 2/844 20130101; A61F 2002/9155
20130101; A61F 2/915 20130101 |
Class at
Publication: |
623/1.15 |
International
Class: |
A61F 002/06 |
Claims
What is claimed is:
1. A post-deployment stent structure for maintaining patency of a
vessel of a human body comprising: a multiplicity of closed,
generally circular rings, the plane of each ring being generally
parallel to the plane of each adjacent ring, the rings having a
common longitudinal axis which is perpendicular to the plane of
each ring and which longitudinal axis passes through the geometric
center of each ring; and a multiplicity of elongated wire
structures forming longitudinals which longitudinals are fixedly
attached to the rings so as to be generally parallel to the
longitudinal axis of the rings.
2. The stent of claim 2 wherein the rings have a multiplicity of
cutouts for the placement therethrough of the longitudinals.
3. The stent of claim 2 wherein the cutouts on the rings are
notches.
4. The stent of claim 3 wherein the notches on the rings are
located at the outside perimeter of each ring.
5. The stent of claim 3 wherein the notches are located at the
inside perimeter of each ring.
6. The stent of claim 2 wherein the cutouts are holes drilled
through the rings.
7. The stent of claim 1 wherein the longitudinals are essentially
straight wires.
8. The stent of claim 1 wherein at least two of the longitudinals
are of an undulating shape.
9. The stent of claim 1 wherein the longitudinals are welded to the
rings.
10. The stent of claim 1 wherein the rings and longitudinals are
made from or coated with titanium.
11. The stent of claim 1 wherein the end rings are more radiopaque
as compared to any other ring.
12. The stent of claim 1 wherein the stent is formed from a metal
having a shape memory characteristic.
13. An intial structure that is capable of being formed into a
pre-deployment stent structure which in turn is capable of being
deployed into a post-deployment stent structure for placement
within a vessel of the human body, the initial stucture comprising:
a multiplicity of flat ovals, the plane of each oval being
generally parallel to the plane of all other ovals, the ovals
having a common longitudinal axis which is perpendicular to the
plane of each oval and which longitudinal axis passes through the
geometric center of the ovals; and a multiplicity of longitudinals
which are fixedly attached to the ovals, the longitudinals being
positioned onto the ovals so as to be generally parallel to the
longitudinal axis of the ovals.
14. The initial structure of claim 12 wherein the ovals and the
longitudinals are formed form a single piece of metal.
15. A generally cylindrical pre-deployment stent structure which is
capable of being deployed into a post-deployment stent structure
for placement within a vessel of the human body, the pre-deployment
structure being formed from an initial structure which consists of
a multiplicity of flat ovals, the plane of each oval being
generally parallel to the plane of all other ovals, the ovals also
having a minor axis and a major axis and a minor axis dimension and
a major axis dimension; the ovals having a common longitudinal axis
which is perpendicular to the plane of each oval and which
longitudinal axis passes through the geometric center of the ovals;
and a multiplicity of longitudinals which are fixedly attached to
the ovals, the longitudinals being positioned onto the ovals so as
to be generally parallel to the longitudinal axis of the ovals; the
pre-deployment stent structure being formed by folding the ovals
around a distal portion of a stent delivery catheter, the
pre-deployment stent structure being adapted to form a
post-deployment stent structure having a multiplicity of generally
circular rings that are formed from the ovals, the circular rings
being joined together by the longitudinals.
16. The pre-deployment stent structure of claim 15 wherein the
ovals are folded around an expandable balloon located near the
distal end of the stent delivery catheter.
17. The pre-deployment stent structure of claim 15 wherein the
ovals are folded around the oval's minor axis to form a generally
cylindrical shape that can be mounted onto a stent delivery
catheter.
18. The pre-deployment stent structure of claim 15 wherein one side
of the ovals is folded in one direction and the opposite side of
the ovals is folded in the opposite direction to form a
pre-deployment structure of a generally cylindrical shape.
19. The pre-deployment stent structure of claim 15 wherein the
outer diameter of the generally cylindrical pre-deployment stent
structure is approximately the same as the minor axis dimension of
the oval.
20. The pre-deployment stent structure of claim 15 wherein the
stent structure is a cylinder formed from a single piece of metal,
the cylinder being slightly smaller in its inside diameter as
compared to the outside diameter of an expandable balloon located
at a distal portion of a stent delivery catheter onto which the
stent structure is mounted.
Description
FIELD OF THE INVENTION
[0001] This invention is in the field of stents for maintaining
patency of any one of a multiplicity of vessels of the human
body.
BACKGROUND OF THE INVENTION
[0002] In the last decade, many different designs of stents have
been used to maintain patency of arteries and other vessels of the
human body. In all such devices, hoop strength is an important
characteristic. Specifically, the stent must have enough hoop
strength to resist the elastic recoil exerted by the vessel into
which the stent is placed. The Mass stent described in the U.S.
Pat. No. 4,553,545 and the Dotter stent described in U.S. Pat. No.
4,503,569 are each open helical coils. The Palmaz stent described
in the U.S. Pat. No. 4,733,665 is of the "chinese finger" design.
The Gianturco-Rubin stent currently sold by Cook, Inc. is another
stent design which like the stents of Mass, Dotter and Palmaz does
not have any closed circular member to optimize hoop strength.
[0003] The ideal arterial stent utilizes a minimum wire size of the
stent elements to minimize thrombosis at the stent site after
implantation. The ideal arterial stent also posses sufficient hoop
strength to resist elastic recoil of the artery. Although the
optimum design for maximizing hoop strength is a closed circular
structure, no prior art stent has been described which has a small
diameter when percutaneously inserted into a vessel and which
expands into the form of multiplicity of closed circular structures
(i.e. rings) when expanded outward against the vessel wall.
BRIEF SUMMARY OF THE PRESENT INVENTION
[0004] The present invention is an expandable stent that can be
used in an artery or any other vessel of the human body which, when
expanded, forms a mutiplicity of generally circular rings whose
closed structure optimizes hoop strength so as to minimize elastic
recoil of the vessel into which the stent is inserted. Furthermore,
the structure of the stent in the present invention is initially in
the form of folded ellipses or ovals which can be formed to a small
diameter for percutaneous insertion by means of a stent delivery
catheter. The ovals are joined to each other by either a straight
or undulating shaped wires which are called longitudinals which
serve to space the deployed rings within the vessel. Straight
longitudinals are used in straight vessels and undulating
longitudinals can be employed in either straight or highly curved
vessels such as some coronary arteries.
[0005] Thus an object of this invention is to provide a stent
having a maximum hoop strength by the employment of closed,
generally circular structures which are in fact rings.
[0006] Another object of this invention is that the rings are
initially in the form of ovals that can be folded to fit onto a
cylindrical structure at a distal portion of a stent delivery
catheter.
[0007] Still another object of this invention is that the fully
deployed rings are spaced apart by means of longitudinals which are
either straight of undulating wires that are placed to be generally
parallel to the longitudinal axis of the vessel into which the
stent is deployed.
[0008] Still another object of this invention is that the
pre-deployment stent structure is formed as a single piece out of a
metal tube having a smaller inside diameter as compared to the
outside diameter of an expandable balloon onto which the
pre-deployment stent is mounted.
[0009] These and other important objects and advantages of this
invention will become apparent from the detailed description of the
invention and the associated drawings provided herein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a side view of the stent after it has been
deployed; i.e., in its post-deployment form.
[0011] FIG. 2 is a transverse cross section at section 2-2 of FIG.
1 illustrating how the longitudinals are joined to the rings.
[0012] FIG. 3 is a cross section at section 3-3 of FIG. 2 showing,
the joining of a single ring to the longitudinals.
[0013] FIG. 4 is a side view of the stent prior to being mounted
onto a stent delivery catheter; i.e., in the form of an initial
structure.
[0014] FIG. 5 is a transverse cross section at section 5-5 of FIG.
4 illustrating how the longitudinals are joined to the ovals.
[0015] FIG. 6 is a side view of a pre-deployment form of the stent
structure in which the ovals have been folded into a small diameter
cylinder that is placed around a deflated balloon situated near the
distal end of a stent delivery catheter.
[0016] FIG. 7 is a partial side view of a pre-deployment stent
structure showing only two of a multiplicity of folded ovals formed
around an expandable balloon in which the ovals are folded in an
alternative manner as compared with FIG. 6.
[0017] FIG. 8 is a side view of a post-deployment stent structure
which utilizes two undulating longitudinals on opposite sides of
the stent for improved placement in curved vessels.
[0018] FIG. 9 is a side view of a stent as etched out of a small
diameter metal cylinder as a single piece of metal.
DETAILED DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a side view of the cylindrical stent 1 of the
present invention shown in its post-deployment configuration. The
stent 1 has a multiplicity of rings 2 which are spaced apart by
four wires called longitudinals. As seen in FIGS. 1 and 2, at the
top of the stent is longitudinal 4T, at the bottom is longitudinal
4B, at the left side is longitudinal 4L and at the right side is
longitudinal 4R. Although FIGS. 1 and 2 show 7 rings and 4
longitudinals, it is apparent that the stent can be made longer by
adding rings or increasing the separation between rings. In a
similar manner, the stent can be made shorter by reducing the
number of rings or decreasing the spacing between rings. Also
variable spacing of the rings is envisioned for accomplishing a
variety of purposes including increased hoop strength at a
particular section of the stent. Also, it is envisioned that the
two or more longitudinals could be utilized for this stent design
with a maximum number being 32.
[0020] FIGS. 2 and 3 illustrate the joining of the longitudinals to
the rings. Specifically the longitudinals can be placed into
cutouts in the form of notches 5 located on the outside perimeter
of the ring 2. The longitudinals can then be spot welded,
adhesively bonded or joined by any variety of means to the rings 2.
It is also envisioned that the longitudinals could be placed on the
inside perimeter of the ring 2, or holes could be mechanically or
laser drilled through the ring X for placement therethrough of the
longitudinals.
[0021] FIGS. 4 and 5 illustrate a stent 1' shown in one particular
form in which it could be fabricated; i.e., in an initial structure
form. Specifically, FIGS. 4 and 5 show that this initial form of
the stent 1' is a multiplicity of parallel ellipses or ovals 2'
each oval having the same minor axis dimension m and major axis
dimension M. The oval's minor axis passes through the center of the
longitudinals 4L and 4R. The oval's major axis passes through the
center of the longitudinals 4T and 4B. It is important to note
that, if it is desired to have a final outside diameter D (as seen
in FIG. 2) of the ring 2 after it is fully deployed, then it can be
shown that D is given by the equation
D.sup.2=1/2(m.sup.2+M.sup.2).
[0022] To place the stent design of FIGS. 4 and 5 onto a balloon
that is mounted near the distal end of a stent delivery catheter,
it is necessary to fold the ovals 2' around that balloon.
Specifically, the pre-deployment cylindrical stent 1" can be formed
onto an expandable balloon 6 as shown in FIG. 6 by folding the
ovals 2' about the dotted line F (which is the minor axis of the
oval 2') as shown in FIG. 5. Specifically, as seen in FIG. 4, the
top and bottom of the ovals 2' could be held stationery while the
side longitudinals 4R and 4L are pushed to the left which results
in the pre-deployment structure which is shown as the stent 1" in
FIG. 6. An optimum design has the folded ovals 2" as shown in FIG.
6 with the stent 1" being a cylinder whose outside diameter is
equal in size to the minor axis dimension m. When the balloon 6 of
FIG. 6 is expanded, the pre-deployment stent 1" structure forms the
post-deployment stent 1 structure having circular rings 2 as shown
in FIGS. 1 and 2.
[0023] Te stent 1'" is an alternative embodiment for a
pre-deployment structure of the stent of the present invention as
it is placed onto a balloon. Specifically, FIG. 7 shows 2 folded
rings 2'" of a multiple ring stent 1'". The stent 1'" being formed
by holding the top and bottom of the stent 1' of FIG. 4 stationery
while pushing the longitudinal 4R to the left and pushing, the
longitudinal 4L to the right. Like the stent 1" of FIG. 6, when
mounted onto a balloon, the stent 1'" has a cylindrical shape with
a diameter equal to the dimension m.
[0024] FIGS. 1 to 7 inclusive illustrate stents that employ
longitudinals that are formed from generally straight wires. FIG. 8
shows an alternative embodiment of a stent 10 that has two
undulating longitudinals. Specifically, the left side longitudinal
14L (shown as dotted lines) and the right side longitudinal 14R are
each undulating shaped longitudinals. A stent such as stent 10
could have two or more undulating longitudinals. Such a stent would
bend more easily during insertion into a vessel and would be more
readily adaptable for placement in curved vessels such as some
coronary arteries.
[0025] Typically, the rings and longitudinals of the stents would
be made of the same material. Typical metals used for such a stent
would be stainless steel, tantulum, titanium, or a shape memory
metal such as Nitinol. If Nitinol is used, the stent would be heat
treated into the shape at body temperature having circular rings 2
as shown in FIGS. 1 and 2. The rings could then be distorted into
ovals as shown in FIGS. 4 and 5 and then mounted onto a stent
delivery catheter which does not employ a balloon but is of the
more general shape described in the previously cited U.S. Pat. No.
4,553,545 by C. T. Dotter. Such a design would provide the desired
stent structure having a multiplicity of generally circular rings
instead of the Dotter design of a helical spring which inherently
has a lesser hoop strength as compared to the present
invention.
[0026] It should be understood that once the ovals are folded onto
a stent delivery catheter, when they fully deploy, they do not form
perfectly circular rings as shown in FIG. 2, but rather they are of
a generally circular shape. Such comparatively small deviations
from an exactly circular shape do not appreciably decrease hoop
strength because they are in fact closed structures that are almost
exactly circular.
[0027] It should also be understood that at least part of the end
rings of the stent could be fabricated from or coated with a
radiopaque metal such as tantalum or gold to provide a fluoroscopic
indication of the stent position within a vessel. However, the
other rings and the longitudinals could be made from a much less
dense metal which would provide less obscuration of the central
region within the stent. For example, the stent rings and
longitudinals could all be fabricated from titanium or a titanium
alloy except the end rings which could be formed from gold which is
then plated with titanium. Thus, the entire outside surface of the
stent would be titanium, which is known to be a comparatively
non-thrombogenic metal while the gold in the end rings provides an
improved fluoroscopic image of the stent extremities.
[0028] The dimensions of stent rings are typically 0.1 to 0.3 mm
thick, with a width of 0.1 to 0.5 mm and an outside diameter D
between 2.0 and 30.0 mm depending on the luminal diameter of the
vessel into which it is inserted. The length of the stent could be
between 1 and 10 cm. The wire diameter for the longitudinals would
typically be between 0.05 and 0.5 mm.
[0029] Although the designs of FIGS. 1 through 7 inclusive
illustrate separate longitudinals attached to a multiplicity of
rings, this invention also contemplates an initial stent structure
which is chemically etched from thin-walled tubing having an oval
transverse cross section. Thus the oval and longitudinals would be
formed from a single piece of metal thus precluding the need for
attaching the longitudinals to the rings. In a similar manner laser
or EDM machining could be used to form the stent from a thin-wailed
tube.
[0030] It is further anticipated that a pre-deployment stent
structure 20 as shown in FIG. 9 could be formed from a thin-walled
cylindrical tube whose inside diameter is slightly smaller than the
outside diameter of the balloon 6 shown in FIG. 6. A pattern such
as that shown in either FIG. 6 or FIG. 7 could be photoetched onto
a thin-walled metal cylinder. The one piece structure 20 shown in
FIG. 9 has folded ovals 22 and longitudinals 23T, 24B, 24R and (not
shown) 24L. This pre-deployment stent structure 20 could then be
mounted onto the expandable balloon; the stent having sufficient
elastic recoil to firmly grasp down onto the balloon.
[0031] Various other modifications, adaptations, and alternative
designs are of course possible in light of the above teachings.
Therefore, it should be understood at this time that within the
scope of the appended claims, the invention may be practiced
otherwise than as specifically described
* * * * *