U.S. patent application number 10/364612 was filed with the patent office on 2003-07-31 for radially-expandable stent and delivery system.
This patent application is currently assigned to Medtronic, Inc.. Invention is credited to Loshakove, Amir, Nativ, Ofer, Wolinsky, Lone.
Application Number | 20030144731 10/364612 |
Document ID | / |
Family ID | 21792010 |
Filed Date | 2003-07-31 |
United States Patent
Application |
20030144731 |
Kind Code |
A1 |
Wolinsky, Lone ; et
al. |
July 31, 2003 |
Radially-expandable stent and delivery system
Abstract
The present invention provides radially-expandable stents that,
in various embodiments, may reduce the bending stresses/strains
associated with the compressed state of self-expanding stents
and/or may prevent longitudinal expansion/contraction of radially
expandable stents between the compressed and expanded states. In
addition, stents according to the present invention preferably
exhibit increased longitudinal flexibility in both the compressed
and expanded states. The present invention also includes delivery
systems in which threading of the guidewire through the delivery
system may be simplified. In addition, the delivery systems
according to the present invention may also incorporate a balloon
to assist in radially expanding the stent and/or seating of the
stent in the lumen during deployment without removing the stent
delivery catheter. Further, the delivery systems may also include a
support tube at the proximal end to assist in fixing the position
of the stent relative to a guide catheter during deployment of the
stent.
Inventors: |
Wolinsky, Lone; (Ramat Gan,
IL) ; Nativ, Ofer; (Rishon LeZion, IL) ;
Loshakove, Amir; (Moshav Burgata, IL) |
Correspondence
Address: |
MUETING, RAASCH & GEBHARDT, P.A.
P.O. BOX 581415
MINNEAPOLIS
MN
55458
US
|
Assignee: |
Medtronic, Inc.
Minneapolis
MN
|
Family ID: |
21792010 |
Appl. No.: |
10/364612 |
Filed: |
February 11, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10364612 |
Feb 11, 2003 |
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09019210 |
Feb 5, 1998 |
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6533807 |
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Current U.S.
Class: |
623/1.16 ;
623/1.11 |
Current CPC
Class: |
A61F 2230/0054 20130101;
A61F 2/91 20130101; A61F 2/95 20130101; A61F 2002/91533 20130101;
A61F 2250/0037 20130101; A61F 2002/91583 20130101; A61F 2/915
20130101; A61F 2/966 20130101 |
Class at
Publication: |
623/1.16 ;
623/1.11 |
International
Class: |
A61F 002/06 |
Claims
What is claimed is:
1. A radially expandable stent for implantation within a body lumen
comprising: an elongated generally tubular body defining a
passageway having a longitudinal axis; the body comprising a
plurality of circumferential support sections arranged successively
along the longitudinal axis, each of the support sections having a
length along the longitudinal axis; each of the circumferential
support sections comprising a plurality of primary bends
interconnected by struts, the primary bends being located on
alternating ends of the support section around the circumference of
the body, each of the struts connecting successive primary bends on
opposite ends of the support section and having a midpoint
generally located therebetween; and at least one longitudinal
member connecting adjacent support sections in the body, the
longitudinal member having a first end attached proximate the
midpoint of one of the struts and a second end attached proximate
the midpoint of one of the struts in the adjacent support section;
wherein the stent is radially compressible into a compressed state
in which the struts are generally aligned with the longitudinal
axis and radially expandable into an expanded state in which the
struts and the primary bends in each of the support sections are
arranged in a zigzag pattern, and further wherein the longitudinal
length of the stent in the compressed state is substantially the
same as the longitudinal length of the stent in the expanded
state.
2. A stent according to claim 1, wherein the body comprises first,
second and third support sections, and further wherein each of the
longitudinal members connecting the first support section to the
second support section are circumferentially offset from each of
the longitudinal members connecting the second support section to
the third support section.
3. A stent according to claim 1, further comprising two or more
longitudinal members connecting adjacent support sections in the
body.
4. A stent according to claim 1, wherein all of the support
sections are in phase with each other.
5. A stent according to claim 1, wherein at least one pair of
adjacent support sections are out of phase with each other.
6. A stent according to claim 1, wherein the body comprises a
nickel titanium alloy.
7. A stent according to claim 1, wherein each primary bend of the
plurality of primary bends connects a pair of struts in the support
section, and further wherein each pair of struts abut at a point
between the primary bend and the midpoint of each of the struts in
the pair of struts when the stent is in the compressed state,
whereby the bending stress is reduced at each primary bend of the
plurality of primary bends.
8. A stent according to claim 7, wherein at least one of the struts
in each pair of struts associated with one of the primary bends
comprises a secondary bend located between the midpoint and one end
of the strut, the secondary bend including an apex facing the other
strut in the pair of struts, and further wherein the point at which
the pair of struts abut is at the apex of the secondary bend when
the stent is in the compressed state.
9. A stent according to claim 7, wherein each strut of the
plurality of struts comprises two secondary bends, one of the
secondary bends located on each side of the midpoint of the strut
and each of the secondary bends being spaced from the ends of the
strut, each of the secondary bends having an apex, wherein the
apexes of each of the secondary bends face the opposing struts in
each pair of struts associated with one of the primary bends in the
support section, and further wherein the point at which each pair
of struts associated with one of the primary bends abut when the
stent is in the compressed state is at the apexes of the secondary
bends of the struts.
10. A stent according to claim 7, wherein at least one of the
struts in each pair of struts associated with one of the primary
bends comprises a protrusion located between the midpoint and one
end of the strut, the protrusion facing the other strut in the pair
of struts, and further wherein the point at which the pair of
struts abut is at the protrusion when the stent is in the
compressed state.
11. A stent according to claim 7, wherein each strut of the
plurality of struts comprises two protrusions, one of the
protrusions located on each side of the midpoint of the strut and
each of the protrusions being spaced from the ends of the strut,
wherein the protrusions face the opposing struts in each pair of
struts associated with one of the primary bends in the support
section, and further wherein the point at which each pair of struts
abut when the stent is in the compressed state is at the
protrusions in each strut in the pair of adjacent struts.
12. A self-expanding radially expandable stent for implantation
within a body lumen comprising: an elongated generally tubular body
defining a passageway having a longitudinal axis, the body
comprising at least one circumferential support section having a
length along the longitudinal axis; each of the circumferential
support sections comprising a plurality of primary bends
interconnected by struts, the primary bends being located on
alternating ends of the support section around the circumference of
the body, each of the struts connecting successive primary bends on
opposite ends of the support section and having a midpoint
generally located therebetween; wherein the stent is radially
compressible into a compressed state and radially expandable into
an expanded state in which the struts and primary bends in each of
the support sections are arranged in a zigzag pattern, and further
wherein each pair of adjacent struts associated with each of the
primary bends abut at a point between the primary bend and the
midpoint of each strut in the pair of adjacent struts when the
stent is in the compressed state, whereby the bending stress is
reduced at each primary bend of the plurality of primary bends.
13. A stent according to claim 12, wherein at least one of the
struts in the pair of struts associated with each of the primary
bends comprises a secondary bend located between the midpoint and
one end of the strut, the secondary bend including an apex facing
the other strut in the pair of struts, and further wherein the
point at which the pair of struts abut is at the apex of the
secondary bend when the stent is in the compressed state.
14. A stent according to claim 12, wherein each strut of the
plurality of struts comprises two secondary bends, one of the
secondary bends located on each side of the midpoint of the strut
and each of the secondary bends being spaced from the ends of the
strut, each of the secondary bends having an apex, wherein the
apexes of each of the secondary bends face the opposing struts in
each pair of struts associated with one of the primary bends in the
support section, and further wherein the point at which each pair
of struts associated with one of the primary bends abut when the
stent is in the compressed state is at the apexes of the secondary
bends of the struts.
15. A stent according to claim 12, wherein at least one of the
struts in each pair of struts associated with one of the primary
bends comprises a protrusion located between the midpoint and one
end of the strut, the protrusion facing the other strut in the pair
of struts, and further wherein the point at which the pair of
struts abut is at the protrusion when the stent is in the
compressed state.
16. A stent according to claim 12, wherein each strut of the
plurality of struts comprises two protrusions, one of the
protrusions located on each side of the midpoint of the strut and
each of the protrusions being spaced from the ends of the strut,
wherein the protrusions face the opposing struts in each pair of
struts associated with one of the primary bends in the support
section, and further wherein the point at which each pair of struts
associated with one of the primary bends abut when the stent is in
the compressed state is at the protrusions in the struts.
17. A self-expanding radially expandable stent for implantation
within a body lumen comprising: an elongated generally tubular body
defining a passageway having a longitudinal axis, the body
comprising at least one circumferential support section having a
length along the longitudinal axis; each of the circumferential
support sections comprising a substantially continuous element
including a plurality of primary bends interconnected by struts,
the primary bends being located on alternating ends of the support
section around the circumference of the body, each of the struts
connecting successive primary bends on opposite ends of the support
section and having a midpoint generally located therebetween,
wherein the stent is radially compressible into a compressed state
and radially expandable into an expanded state in which the struts
and primary bends in each of the support sections are arranged in a
zigzag pattern; and means for reducing bending stress at the
primary bends when the stent is in the compressed state.
18. A stent according to claim 17, wherein the means for reducing
bending stress causes each pair of struts associated with one of
the primary bends to abut at a point between the midpoints of the
pair of struts and the primary bend.
19. A stent according to claim 17, wherein the body comprises a
plurality of circumferential support sections arranged successively
along the longitudinal axis, and further wherein the body comprises
at least one longitudinal member connecting adjacent support
sections in the body, the longitudinal member having a first end
attached to one of the support sections and a second end attached
to the adjacent support section.
20. A stent according to claim 19, wherein the first end of each of
the longitudinal members is attached proximate the midpoint of one
of the struts in one of the support sections and the second end of
each of the longitudinal members is attached proximate the midpoint
of one of the struts in an adjacent support section; wherein the
longitudinal length of the stent in the compressed state is
substantially the same as the longitudinal length of the stent in
the expanded state.
21. A delivery system for implantation of a radially-expandable
stent within a body lumen comprising: an inner tube having a
proximal end and a distal end, the inner tube having an inner tube
lumen formed therein, the inner tube lumen having an opening at the
distal end of the inner tube; a cover sheath having a proximal end
and a distal end, the cover sheath comprising a wall defining a
cover sheath lumen, the inner tube located within the cover sheath
lumen; a stent positioned about the inner tube at the distal end of
the cover sheath; a first guidewire opening in the inner tube
lumen, the first guidewire opening spaced from the distal end of
the inner tube; a second guidewire opening in the wall of the cover
sheath, the second guidewire opening located proximate the first
guidewire opening; and a guide element having a distal end located
within the inner tube lumen, the guide element extending between
the first and second guidewire openings.
22. A system according to claim 21, wherein the guide element
comprises a proximal end located outside of the cover sheath lumen
such that the guide element extends through the second guidewire
opening.
23. A system according to claim 21, wherein the guide element is
removably positioned in the inner tube lumen and the first and
second guidewire openings.
24. A system according to claim 21, wherein the inner tube lumen
terminates at the first guidewire opening.
25. A system according to claim 21, wherein the first guidewire
opening is formed in an inner tube wall.
26. A system according to claim 21, wherein the guide element
comprises a guide lumen formed in the distal end of the guide
element.
27. A system according to claim 26, wherein the guide lumen can
receive only a portion of the guidewire.
28. A system according to claim 21, wherein the stent is
self-expanding and comprises: an elongated generally tubular body
defining a passageway having a longitudinal axis, the body
comprising at least one circumferential support section having a
length along the longitudinal axis; each of the circumferential
support sections comprising a plurality of primary bends
interconnected by struts, the primary bends being located on
alternating ends of the support section around the circumference of
the body, each of the struts connecting successive primary bends on
opposite ends of the support section and having a midpoint
generally located therebetween; wherein the stent is radially
compressible into a compressed state and radially expandable into
an expanded state in which the struts and primary bends in each of
the support sections are arranged in a zigzag pattern, and further
wherein each pair of adjacent struts associated with each of the
primary bends abut at a point between the primary bend and the
midpoint of each strut in the pair of adjacent struts when the
stent is in the compressed state, whereby the bending stress is
reduced at each primary bend of the plurality of primary bends.
29. A system according to claim 28, wherein the stent is biased
against the interior surface of the cover sheath in the compressed
state, and further wherein the inner tube comprises a shoulder
having an outside diameter greater than an inside diameter of the
stent in the compressed state within the cover sheath, whereby
movement of the cover sheath proximally forces the stent out of the
cover sheath.
30. A system according to claim 28, wherein at least one of the
struts in the pair of struts associated with each of the primary
bends comprises a secondary bend located between the midpoint and
one end of the strut, the secondary bend including an apex facing
the other strut in the pair of struts, and further wherein the
point at which the pair of struts abut is at the apex of the
secondary bend when the stent is in the compressed state.
31. A stent according to claim 28, wherein at least one of the
struts in each pair of struts associated with one of the primary
bends comprises a protrusion located between the midpoint and one
end of the strut, the protrusion facing the other strut in the pair
of struts, and further wherein the point at which the pair of
struts abut is at the protrusion when the stent is in the
compressed state.
32. A stent according to claim 28, wherein the body comprises a
plurality of circumferential support sections arranged successively
along the longitudinal axis, and further wherein the body comprises
at least one longitudinal member connecting adjacent support
sections in the body, the longitudinal member having a first end
attached proximate the midpoint of one of the struts in one of the
support sections and a second end attached proximate the midpoint
of one of the struts in an adjacent support section; wherein the
longitudinal length of the stent in the compressed state is
substantially the same as the longitudinal length of the stent in
the expanded state.
33. A system according to claim 32, wherein the body of the stent
comprises first, second and third support sections, and further
wherein each of the longitudinal members connecting the first
support section to the second support section are circumferentially
offset from each of the longitudinal members connecting the second
support section to the third support section.
34. A system according to claim 21, further comprising: an
expandable balloon located on the inner tube; and an inflation
lumen in fluid communication with the balloon, the inflation lumen
extending from the proximal end of the delivery system to the
balloon.
35. A system according to claim 34, wherein the balloon is located
between the stent and the inner tube.
36. A method of deploying a stent within a body lumen comprising:
a) providing a radially expandable stent on a delivery system
comprising: an inner tube having a proximal end and a distal end,
the inner tube having an inner tube lumen formed therein, the inner
tube lumen having an opening at the distal end of the inner tube
and a first guidewire opening in the inner tube lumen, the first
guidewire opening spaced from the distal end of the inner tube; a
stent positioned on the exterior surface of the inner tube at the
distal end of the inner tube; a cover sheath having a proximal end
and a distal end, the cover sheath comprising a wall defining a
cover sheath lumen, the inner tube and stent located within the
cover sheath lumen, the cover sheath further including a second
guidewire opening in the wall of the cover sheath, the second
guidewire opening located proximate the first guidewire opening in
the inner tube; and a guide element having a distal end located
within the inner tube lumen, the guide element extending between
the first and second guidewire openings, wherein the guide element
comprises a guide lumen formed in the distal end of the guide
element; b) positioning a guidewire within a body lumen, wherein a
proximal end of the guidewire extends out of the body lumen; c)
inserting the proximal end of the guidewire into the inner tube
lumen at the distal end of the inner tube; d) advancing the
proximal end of the guidewire through the inner tube lumen towards
the first guidewire opening and the distal end of the guide
element, wherein at least a portion of the proximal end of the
guidewire is advanced into the guide lumen in the distal end of the
guide element; e) advancing the proximal end of the guidewire
through the first and second guidewire openings; f) advancing the
distal end of the inner tube and the stent over the guidewire
towards the distal end of the guidewire, wherein the stent is
positioned at a desired location within the body lumen; and g)
deploying the stent at the desired location within the body
lumen.
37. A method according to claim 36, wherein the guide element is
removably positioned in the inner tube lumen and the first and
second guidewire openings, and further wherein the step of
advancing the proximal end of the guidewire through the first and
second guidewire openings further comprises moving the guide
element out of the first and second guidewire openings.
38. A method according to claim 36, wherein the guide lumen can
receive only a portion of the proximal end of the guidewire.
39. A method according to claim 36, wherein the guide element
comprises a proximal end located outside of the cover sheath lumen
such that the guide element extends through the second guidewire
opening.
40. A method of deploying a stent within a body lumen comprising:
a) providing a radially expandable stent on a delivery system
comprising: an inner tube having a proximal end and a distal end,
the inner tube having an inner tube lumen formed therein; a stent
positioned on the exterior surface of the inner tube at the distal
end of the inner tube; an expandable balloon located on the inner
tube; an inflation lumen in fluid communication with the balloon,
the inflation lumen extending from the proximal end of the delivery
system to the balloon; and a cover sheath having a proximal end and
a distal end, the cover sheath comprising a wall defining a cover
sheath lumen, the inner tube, stent, and balloon located within the
cover sheath lumen; b) positioning the inner tube, stent, balloon
and cover sheath within a body lumen; c) moving the cover sheath
proximally relative to the distal end of the inner tube to deploy
the stent with the body lumen; and d) inflating the balloon within
the stent.
41. A method according to claim 40, wherein the balloon is located
between the stent and the inner tube.
42. A method of deploying a stent within a body lumen comprising:
a) providing a radially expandable stent on a delivery system
comprising: an inner tube having a proximal end and a distal end; a
stent positioned on the exterior surface of the inner tube at the
distal end of the inner tube; a cover sheath having a proximal end
and a distal end, the cover sheath including a cover sheath lumen,
the inner tube and stent located within the cover sheath lumen; and
a support tube having a proximal end and a distal end, the support
tube including a support tube lumen containing at least a portion
of the proximal end of the cover sheath, the cover sheath being
movable in the proximal and distal directions within the support
tube lumen and the position of the inner tube being fixed relative
to the position of the support tube; b) positioning a guide
catheter within a body lumen; c) advancing the distal ends of the
inner tube and the cover sheath through the guide catheter; d)
fixing the position of the support tube relative to the guide
catheter, wherein the positions of the distal end of the inner tube
and the stent within the body lumen are also fixed relative to the
guide catheter; and e) moving the cover sheath proximally to
release the stent on the distal end of the inner tube, thereby
deploying the stent within the body lumen.
43. A method according to claim 42, wherein the guide catheter
includes a hemostasis valve and further wherein the step of fixing
the position of the support tube relative to the guide catheter
comprises closing the hemostasis valve on the support tube.
44. A method according to claim 42, wherein the support tube and
the inner tube are fixedly attached to a handle and the cover
sheath is attached to an actuator, the actuator movable relative to
the handle, and further wherein the step of moving the cover sheath
comprises moving the actuator relative to the handle.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to intravascular stent
implants for maintaining vascular patency in humans and animals.
More particularly, the present invention provides a
radially-expandable stent and a delivery system for delivering a
radially-expandable stent within a body lumen.
BACKGROUND OF THE INVENTION
[0002] Percutaneous transluminal coronary angioplasty (PTCA) is
used to increase the lumen diameter of a coronary artery partially
or totally obstructed by a build-up of cholesterol fats or
atherosclerotic plaque. Typically a first guidewire of about 0.038
inches in diameter is steered through the vascular system to the
site of therapy. A guiding catheter, for example, can then be
advanced over the first guidewire to a point just proximal of the
stenosis. The first guidewire is then removed. A balloon catheter
on a smaller 0.014 inch diameter second guidewire is advanced
within the guiding catheter to a point just proximal of the
stenosis. The second guidewire is advanced into the stenosis,
followed by the balloon on the distal end of the catheter. The
balloon is inflated causing the site of the stenosis to widen.
[0003] The dilatation of the occlusion, however, can form flaps,
fissures and dissections which threaten reclosure of the dilated
vessel or even perforations in the vessel wall. Implantation of a
stent can provide support for such flaps and dissections and
thereby prevent reclosure of the vessel or provide a patch repair
for a perforated vessel wall until corrective surgery can be
performed. It has also been shown that the use of intravascular
stents can measurably decrease the incidence of restenosis after
angioplasty thereby reducing the likelihood that a secondary
angioplasty procedure or a surgical bypass operation will be
necessary.
[0004] An implanted prosthesis such as a stent can preclude
additional procedures and maintain vascular patency by mechanically
supporting dilated vessels to prevent vessel reclosure. Stents can
also be used to repair aneurysms, to support artificial vessels as
liners of vessels or to repair dissections. Stents are suited to
the treatment of any body lumen, including the vas deferens, ducts
of the gallbladder, prostate gland, trachea, bronchus and liver.
The body lumens range in diameter from small coronary vessels of 3
mm or less to 28 mm in the aortic vessel. The invention applies to
acute and chronic closure or reclosure of body lumens.
[0005] A typical stent is a cylindrically shaped wire formed device
intended to act as a permanent prosthesis. A typical stent ranges
from 5 mm to 50 mm in length. A stent is deployed in a body lumen
from a radially compressed configuration into a radially expanded
configuration which allows it to contact and support a body lumen.
The stent can be made to be radially self-expanding or expandable
by the use of an expansion device. The self expanding stent is made
from a resilient springy material while the device expandable stent
is made from a material which is plastically deformable. A
plastically deformable stent can be implanted during a single
angioplasty procedure by using a balloon catheter bearing a stent
which has been crimped onto the balloon. The stent expands radially
as the balloon is inflated forcing the stent into contact with the
interior of the body lumen thereby forming a supporting
relationship with the vessel walls.
[0006] Conventional angioplasty balloons fall into high, medium and
low pressure ranges. Low pressure balloons are those which fall
into rated burst pressures below 6 atmospheres. Medium pressure
balloons are those which fall into rated burst pressures between 6
and 12 atmospheres. High pressure balloons are those which fall
into rated burst pressures above 12 atmospheres. Burst pressure is
determined by material selection, wall thickness and tensile
strength.
[0007] The biocompatible metal stent props open blocked coronary
arteries, keeping them from reclosing after balloon angioplasty. A
balloon of appropriate size and pressure is first used to open the
lesion. The process is repeated with a stent crimped on a second
balloon. The second balloon may be a high pressure type of balloon,
e.g., more than 12 atmospheres, to insure that the stent is fully
deployed upon inflation. The stent is deployed when the balloon is
inflated. The stent remains as a permanent scaffold after the
balloon is withdrawn. A high pressure balloon is preferable for
stent deployment because the stent must be forced against the
artery's interior wall so that it will fully expand thereby
precluding the ends of the stent from hanging down into the channel
encouraging the formation of thrombus.
[0008] Various shapes of stents are known in the art. U.S. Pat. No.
4,649,922 (Wiktor) discloses a linearly expandable spring-like
stent. U.S. Pat. No. 4,886,062 (Wiktor) discloses a two-dimensional
zigzag form, typically a sinusoidal form. U.S. Pat. No. 4,969,458
(Wiktor) discloses a stent wire coiled into a limited number of
turns wound in one direction, then reversed and wound in the
opposite direction with the same number of turns, then reversed
again and so on until a desired length is obtained.
[0009] Stents have limited ability to provide effective patching of
perforated vessels due to the spacing between metal elements. U.S.
Pat. No. 4,878,906 (Lindeman et al.) describes an endoprosthesis
made of a thin wall molded plastic sleeve intended to be collapsed
radially and delivered to a damaged area of a vessel where it is
expanded to provide a sealed interface to the vessel on its outer
peripheral ends. The endoprosthesis therefore provides a patch
which prevents leakage of blood from a vessel wall. The
endoprosthesis disclosed employs various molded-in ribs, struts and
the like to adapt the device for particular applications and to
provide the desired degree of stiffness to form the sealed
interface with the vessel wall. Such a stiff prosthesis, however,
could not be expected to have the longitudinal flexibility needed
to adapt to curved vessels.
[0010] One problem with self-expanding stents is that the stents
must be compressed into a small diameter for delivery to the site
or portion of the body lumen at which support is desired. It is
preferable that the stents be compressed into as small of a
diameter as possible (typically referred to as "profile") to assist
in delivering the stent to the desired site. That compression can,
in some cases cause localized areas of high bending stress/strain
within the stent.
[0011] As a result of the high bending stresses/strain, the minimum
profile for the self-expanding stents can be limited to prevent
non-recoverable strain levels in the stent and, therefore, ensure
full radial expansion of the stent when released from the delivery
system. The larger profile can limit the delivery and use of the
stent to larger diameter lumens.
[0012] Alternatively, if a small delivery profile is desired, then
the stent may be designed to achieve that profile which can often
result in a larger window area and a reduction in the outward
forces generated by the stent after expansion within the lumen. The
larger window area and, therefore, inferior body lumen scaffolding
reduces the effectiveness against recurring restenosis. The reduced
outward forces may be problematic if the stent does not firmly
engage the wall of the lumen.
[0013] One attempt at addressing the high bending stresses/strains
in a self-expanding stent is described in U.S. Pat. No. 4,830,003
(Wolff et al.) in which the stent is made of a series of generally
straight wire segments welded together at their ends to form a
zigzag shaped stent when expanded. By using generally straight
wires, the bending stresses/strains associated with bends in an
integral wire-formed stent body can be avoided. Disadvantages
associated with this approach include, however, the cost of
manufacturing the stents by welding. The welds also lower the
allowable stress levels in the stent, thereby limiting its fatigue
life and compression for delivery. Another disadvantage is that the
length of the stent can change significantly from the compressed
state to the expanded state, thereby making accurate placement of
the stent at the desired location within a body lumen more
difficult.
[0014] Another attempt at addressing the high bending
stresses/strains includes manufacturing self-expanding stents from
materials other than metals as described in, e.g., U.S. Pat. No.
5,356,423 (Tihon et al.). The stents disclosed therein are formed
of thermoplastic materials and can be molded or otherwise formed
into a fenestrated pattern similar to those produced by braided
wire stents. By shaping the openings as depicted in FIG. 5 of the
patent, the stress concentration at the bending points can be
reduced. Disadvantages of this approach include, however,
degradation associated with implanted plastic materials, including
changes in the elasticity of the plastics which can result in a
reduction in the radially outward forces generated by the
stent.
SUMMARY OF THE INVENTION
[0015] It is an object of the invention to provide a self-expanding
stent for implantation within a body lumen that provides for
reductions in the bending stresses/strains associated with
compression of the stent for delivery to the desired location
within a body lumen.
[0016] It is another object of the present invention to provide a
self-expanding stent in which the longitudinal length of the stent
remains unchanged from the compressed state to the expanded
state.
[0017] It is a further object of the invention to provide a stent
with improved longitudinal flexibility to allow for threading
through tortuous lumens and lesions, as well as to permit
implantation in highly curved lumens.
[0018] It is an object of some delivery systems according to the
present invention to provide a delivery system in which the
position of the stent can be fixed relative to a guide
catheter.
[0019] It is another object of some delivery systems according to
the present invention to provide a balloon integral with the stent
delivery device to allow for post-deployment dilatation of the
stent without removing the stent delivery catheter.
[0020] It is another object of some delivery systems of the present
invention to provide for simplified threading of a guidewire
through a distal portion of a rapid-exchange delivery system.
[0021] In one aspect, the present invention provides radially
expandable stent for implantation within a body lumen including an
elongated generally tubular body defining a passageway having a
longitudinal axis; the body including a plurality of
circumferential support sections arranged successively along the
longitudinal axis, each of the support sections having a length
along the longitudinal axis; each of the circumferential support
sections including a plurality of primary bends interconnected by
struts, the primary bends being located on alternating ends of the
support section around the circumference of the body, each of the
struts connecting successive primary bends on opposite ends of the
support section and having a midpoint generally located
therebetween; and at least one longitudinal member connecting
adjacent support sections in the body, the longitudinal member
having a first end attached proximate the midpoint of one of the
struts and a second end attached proximate the midpoint of one of
the struts in the adjacent support section; wherein the stent is
radially compressible into a compressed state in which the struts
are generally aligned with the longitudinal axis and radially
expandable into an expanded state in which the struts and the
primary bends in each of the support sections are arranged in a
zigzag pattern, and further wherein the longitudinal length of the
stent in the compressed state is substantially the same as the
longitudinal length of the stent in the expanded state.
[0022] In another aspect the present invention provides a
self-expanding radially expandable stent for implantation within a
body lumen including an elongated generally tubular body defining a
passageway having a longitudinal axis, the body including at least
one circumferential support section having a length along the
longitudinal axis; each of the circumferential support sections
including a plurality of primary bends interconnected by struts,
the primary bends being located on alternating ends of the support
section around the circumference of the body, each of the struts
connecting successive primary bends on opposite ends of the support
section and having a midpoint generally located therebetween;
wherein the stent is radially compressible into a compressed state
and radially expandable into an expanded state in which the struts
and primary bends in each of the support sections are arranged in a
zigzag pattern, and further wherein each pair of adjacent struts
associated with each of the primary bends abut at a point between
the primary bend and the midpoint of each strut in the pair of
adjacent struts when the stent is in the compressed state, whereby
the bending stress is reduced at each primary bend of the plurality
of primary bends.
[0023] In another aspect, the present invention provides a
self-expanding radially expandable stent for implantation within a
body lumen including an elongated generally tubular body defining a
passageway having a longitudinal axis, the body including at least
one circumferential support section having a length along the
longitudinal axis; each of the circumferential support sections
including a substantially continuous element including a plurality
of primary bends interconnected by struts, the primary bends being
located on alternating ends of the support section around the
circumference of the body, each of the struts connecting successive
primary bends on opposite ends of the support section and having a
midpoint generally located therebetween, wherein the stent is
radially compressible into a compressed state and radially
expandable into an expanded state in which the struts and primary
bends in each of the support sections are arranged in a zigzag
pattern; and means for reducing bending stress at the primary bends
when the stent is in the compressed state.
[0024] In another aspect, the present invention provides a delivery
system for implantation of a radially-expandable stent within a
body lumen including an inner tube having a proximal end and a
distal end, the inner tube having an inner tube lumen formed
therein, the inner tube lumen having an opening at the distal end
of the inner tube; a cover sheath having a proximal end and a
distal end, the cover sheath comprising a wall defining a cover
sheath lumen, the inner tube located within the cover sheath lumen;
a stent positioned about the inner tube at the distal end of the
cover sheath; a first guidewire opening in the inner tube lumen,
the first guidewire opening spaced from the distal end of the inner
tube; a second guidewire opening in the wall of the cover sheath,
the second guidewire opening located proximate the first guidewire
opening; and a guide element having a distal end located within the
inner tube lumen, the guide element extending between the first and
second guidewire openings.
[0025] In another aspect, the present invention provides a method
of deploying a stent within a body lumen by providing a radially
expandable stent on a delivery system including an inner tube
having a proximal end and a distal end, the inner tube having an
inner tube lumen formed therein, the inner tube lumen having an
opening at the distal end of the inner tube and a first guidewire
opening in the inner tube lumen, the first guidewire opening spaced
from the distal end of the inner tube; a stent positioned on the
exterior surface of the inner tube at the distal end of the inner
tube; a cover sheath having a proximal end and a distal end, the
cover sheath comprising a wall defining a cover sheath lumen, the
inner tube and stent located within the cover sheath lumen, the
cover sheath further including a second guidewire opening in the
wall of the cover sheath, the second guidewire opening located
proximate the first guidewire opening in the inner tube; and a
guide element having a distal end located within the inner tube
lumen, the guide element extending between the first and second
guidewire openings, wherein the guide element comprises a guide
lumen formed in the distal end of the guide element; positioning a
guidewire within a body lumen, wherein a proximal end of the
guidewire extends out of the body lumen; inserting the proximal end
of the guidewire into the inner tube lumen at the distal end of the
inner tube; advancing the proximal end of the guidewire through the
inner tube lumen towards the first guidewire opening and the distal
end of the guide element, wherein at least a portion of the
proximal end of the guidewire is advanced into the guide lumen in
the distal end of the guide element; advancing the proximal end of
the guidewire through the first and second guidewire openings;
advancing the distal end of the inner tube and the stent over the
guidewire towards the distal end of the guidewire, wherein the
stent is positioned at a desired location within the body lumen;
and deploying the stent at the desired location within the body
lumen.
[0026] In another aspect, the present invention provides a method
of deploying a stent within a body lumen by providing a radially
expandable stent on a delivery system including an inner tube
having a proximal end and a distal end, the inner tube having an
inner tube lumen formed therein; a stent positioned on the exterior
surface of the inner tube at the distal end of the inner tube; an
expandable balloon located on the inner tube; an inflation lumen in
fluid communication with the balloon, the inflation lumen extending
from the proximal end of the delivery system to the balloon; and a
cover sheath having a proximal end and a distal end, the cover
sheath comprising a wall defining a cover sheath lumen, the inner
tube, stent, and balloon located within the cover sheath lumen;
positioning the inner tube, stent, balloon and cover sheath within
a body lumen; moving the cover sheath proximally relative to the
distal end of the inner tube to deploy the stent with the body
lumen; and inflating the balloon within the stent.
[0027] In another aspect, the present invention provides a method
of deploying a stent within a body lumen by providing a radially
expandable stent on a delivery system including an inner tube
having a proximal end and a distal end; a stent positioned on the
exterior surface of the inner tube at the distal end of the inner
tube; a cover sheath having a proximal end and a distal end, the
cover sheath including a cover sheath lumen, the inner tube and
stent located within the cover sheath lumen; and a support tube
having a proximal end and a distal end, the support tube including
a support tube lumen containing at least a portion of the proximal
end of the cover sheath, the cover sheath being movable in the
proximal and distal directions within the support tube lumen and
the position of the inner tube being fixed relative to the position
of the support tube; positioning a guide catheter within a body
lumen; advancing the distal ends of the inner tube and the cover
sheath through the guide catheter; fixing the position of the
support tube relative to the guide catheter, wherein the positions
of the distal end of the inner tube and the stent within the body
lumen are also fixed relative to the guide catheter; and moving the
cover sheath proximally to release the stent on the distal end of
the inner tube, thereby deploying the stent within the body
lumen.
[0028] These and other features and advantages of the present
invention are described below in connection the description of the
preferred embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] FIG. 1 is a perspective view of one radially expanded stent
according to the present invention.
[0030] FIG. 2 is a plan view of the stent of FIG. 1 in which the
body of the stent is unrolled.
[0031] FIG. 3 is an enlarged partial view of the stent body of FIG.
2 in the expanded state.
[0032] FIG. 4 is an enlarged partial view of the stent body of FIG.
2 in the compressed state.
[0033] FIGS. 5-8 are enlarged partial views of portions of
alternative stents according to the present invention.
[0034] FIG. 9 is a schematic diagram of one delivery system
according to the present invention.
[0035] FIG. 10 is an enlarged cross-sectional view of the delivery
system of FIG. 9 taken along line 10-10 in FIG. 9.
[0036] FIG. 11 is an enlarged cross-sectional view of the distal
end of the delivery system of FIG. 9.
[0037] FIG. 12 is an enlarged cross-sectional view of the distal
end of an alternate delivery system incorporating a balloon.
[0038] FIG. 13 is an enlarged partial cross-sectional view of one
rapid-exchange delivery system according to the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0039] The present invention includes radially-expandable stents
that, in various embodiments, may reduce the bending
stresses/strains associated with the compressed state of
self-expanding stents and/or may prevent longitudinal
expansion/contraction of radially expandable stents between the
compressed and expanded states. In addition, stents according to
the present invention preferably exhibit increased longitudinal
flexibility in both the compressed and expanded states.
[0040] The present invention also includes delivery systems in
which threading of the guidewire through the delivery system may be
simplified. In addition, the delivery systems according to the
present invention may also incorporate a balloon to assist in
radially expanding the stent and/or seating of the stent in the
lumen during deployment without removing the stent delivery
catheter. Further, the delivery systems may also include a support
tube at the proximal end to assist in fixing the position of the
stent relative to a guide catheter during deployment of the
stent.
[0041] Although the following discussion, along with the figures,
describes illustrative preferred embodiments and methods according
to the present invention, those skilled in the art will understand
that other structures and/or methods could also be used to
accomplish the desired functions. For example, although stents
having one or more support sections are described herein, it will
be understood that stents manufactured according to the present
invention could have any number of desired support sections needed
to obtain a stent with a desired longitudinal length. Furthermore,
it will be understood that the figures are schematic only, and that
the relative dimensions of the various illustrated features are not
intended to limit the scope of the present invention.
[0042] FIG. 1 depicts one illustrative self-expanding stent
according to the present invention. The depicted stent includes a
generally tubular body 10 defining a passageway 12 extending along
a longitudinal axis 14. The body 10 is preferably formed from a
plurality of support sections 20a, 20b, 20c, 20d, 20e, and 20f
(collectively referred to as support sections 20 below) arranged
successively along the longitudinal axis 14. The body 10 is
depicted in FIG. 1 in its expanded state in which the support
sections 20 have been expanded radially outward from the
longitudinal axis 14.
[0043] FIG. 2 is a plan view of a portion of the body 10 of the
stent depicted in FIG. 1 in which the body has been unrolled from
the tubular shape of FIG. 1. Each of the support sections 20 is
depicted and has a length along the longitudinal axis 14.
[0044] Referring specifically to support section 20a, the support
section 20a includes a plurality of primary bends 22 and 22'
located on alternating ends of the support section 20a. Primary
bend 22 on one end of the support section 20a is connected to a
primary bend 22' by a strut 24. Because of the alternating nature
of the primary bends 22 and 22', the primary bends 22/22' and
struts 24 are arranged in a zigzag pattern when the stent is in the
expanded state (as in FIGS. 1 and 2).
[0045] Adjacent support sections 20a and 20b are connected to each
other by at least one longitudinal member 40 extending between the
support sections 20a and 20b. It is preferred that the longitudinal
members 40 are attached to the struts 24, although they may be
attached at any location on each of the support sections 20. More
preferably, the longitudinal members 40 are attached to the struts
24 at the midpoint of the length of the struts 24 between the
primary bends 22 and 22'. By attaching the longitudinal members 40
at the midpoints of the struts, the length of the body 10 of the
stent along the longitudinal axis 14 will exhibit substantially no
change between the compressed state and the expanded state.
[0046] Although most of the adjacent support sections 20 are
connected by only one longitudinal member 40 in FIG. 2, it should
be noted that a plurality of longitudinal members 40 can be used to
connect the support sections 20. For example, support sections 20c
and 20d are connected by two longitudinal members 40 in FIG. 2.
Where more than one longitudinal member 40 is used to connect
adjacent support sections 20, it is preferred that the longitudinal
members be spaced evenly about the circumference of the body 10.
For example, where two longitudinal members 40 are provided, it is
preferred that they be located about 180 degrees apart, three
longitudinal members 40 would preferably be located about 120
degrees apart, etc.
[0047] It may be preferred (but not required) that smaller stents,
i.e., those having a diameter as manufactured of about 6
millimeters or less, employ two or more longitudinal members 40 to
connect adjacent support sections 20. It may also be preferred (but
not required) that larger stents, i.e., those having manufactured
diameters of about 5 millimeters or more, employ three or more
longitudinal members 40 to connect adjacent support sections 20.
The exact number of longitudinal members used in any stent
according to the present invention will, however, vary based on the
need for longitudinal flexibility
[0048] It is preferred that the longitudinal members 40 connecting
immediately adjacent support sections 20 are not aligned along the
longitudinal axis 14 of the stent. As one example of this, the
arrangement of the longitudinal members 40 in the first three
support sections 20a, 20b, and 20c can be described. As can be seen
in FIG. 2, the longitudinal members 40 connecting support sections
20a and 20b are not aligned along the longitudinal axis 14 with the
longitudinal members 40 connecting support sections 20b and 20c. It
is generally preferred that the longitudinal members connecting,
e.g., support sections 20a and 20b, be tangentially out of phase
from longitudinal members 40 connecting support sections 20b and
20c by as large an amount as possible. For example, if the support
sections 20a, 20b and 20c are all connected to their adjacent
support sections 20 by two longitudinal members 180 degrees apart,
it is preferred that the longitudinal members 40 connecting support
sections 20a and 20b be tangentially out of phase by 90 degrees
from the longitudinal members 40 connecting the support sections
20b and 20c.
[0049] Providing longitudinal members 40 connecting immediately
adjacent support sections 20, e.g., 20a and 20b, circumferentially
spaced about the support sections 20 can improve the flexibility of
the body 10 along the longitudinal axis 14. In addition, providing
the longitudinal members 40 tangentially out of phase along the
length of the body 10, e.g., between sections 20a-20b and 20b-20c,
can also improve the longitudinal flexibility of stents according
to the present invention. Although these concepts have been
described with reference to three successive support sections, it
will be understood that these concepts can be extended along the
entire length of a stent incorporating as few as two support
sections and as many support sections as desired.
[0050] It is significant to note that the longitudinal bending
flexibility is improved both when the stent is in the compressed
state during delivery and upon deployment of the stent in a body
lumen. Increased longitudinal bending flexibility when compressed
permits threading of the stent through long tortuous vessels and
lesions. Increased longitudinal bending flexibility when expanded
allows for deployment in highly curved vessels or lumens.
[0051] It will be understood that the longitudinal members 40
described above may be incorporated into self-expanding stents or
into stents that are not self-expanding, i.e., stents that must be
expanded by a balloon or some other method. In addition, the
connection of the longitudinal members 40 can be used in any stent
providing zigzag support sections, whether the stent includes
primary bends such as those described herein or not. In any case,
the connection of the longitudinal members 40 the midpoints of the
struts 24 in adjacent zigzag support sections 20 will prevent
changes in the longitudinal length of stents incorporating zigzag
support sections similar to those described herein.
[0052] FIG. 3 is an enlarged view of a portion of the one of the
support sections 20 in FIG. 2. A primary bend 22 is shown along
with two opposing primary bends 22' on the opposite end of the
support section. The primary bend 22 is attached to a pair of
struts 24a and 24b. The lower strut 24a is attached to the lower
opposing primary bend 22' while the upper strut 24b is attached to
the upper opposing primary bend 22'. Strut 24a has a midpoint 25a
that is generally located midway between the primary bend 22 and
the lower opposing primary bend 22' while strut 24b has a midpoint
25b that is generally located midway between the primary bend 22
and the upper opposing primary bend 22'.
[0053] Strut 24a includes a secondary bend 26a located between its
midpoint 25a and the primary bend 22. The secondary bend 26a forms
an apex 27a facing the other strut 24b attached to the primary bend
22. Strut 24b includes a secondary bend 26b located between its
midpoint 25b and the primary bend 22. The secondary bend 26b forms
an apex 27b facing the other strut 24a attached to the primary bend
22. As depicted in FIGS. 2 and 3, it is preferred that each of the
struts 24 connecting primary bends 22 and 22' include two secondary
bends, with one secondary bend being located on each side of the
midpoint of the strut 24.
[0054] FIG. 4 depicts the portion of the support section of FIG. 3
in the compressed state in which the opposing upper and lower
primary bends 22' are moved together. As a result, the struts 24a
and 24b are also moved together, and abut each other first at a
point between the midpoints 25a and 25b of the respective struts
24a and 24b. In the embodiment depicted in FIGS. 3 and 4, the point
at which the struts associated with or attached to the primary bend
22 abut first is at the apexes 27a and 27b of the struts 24a and
24b. As a result, the minimum radius formed by the primary bend 22
during compression of the stent is limited by the abutting
relationship of the apexes 27a and 27b that redistributes the
stresses associated with compression of the stent into the struts
24a and 24b.
[0055] The construction of the supports sections depicted in FIGS.
2-4 can be modified while still limiting the maximum stresses
associated with compression of the stent. One alternative is
depicted in FIG. 5 and includes a primary bend 122 on one end of a
support section and two opposing primary bends 122' on the opposing
end of the support section. The strut 124a connecting the primary
bend 122 with the lower opposing primary bend 122' includes a
secondary bend 126a and the strut 124b connecting the primary bend
122 with the upper opposing primary bend 122' includes a secondary
bend 126b.
[0056] The primary difference between the embodiments depicted in
FIGS. 3 and 5 is that the portion 123a of the strut 124a between
the secondary bend 126a and the primary bend 122 is not generally
parallel to the corresponding portion 123b of the strut 124b. As
described with respect to the embodiment of FIG. 3 above, however,
it is preferred that the struts 124a and 124b abut first at the
apexes 127a and 127b formed by the secondary bends 126a and 126b
during compression to thereby reduce the maximum bending stresses
associated with compression of the stent.
[0057] Another alternative construction is depicted in FIG. 6 and
includes a primary bend 222 on one end of a support section and two
opposing primary bends 222' on the opposing end of the support
section. The strut 224a connecting the primary bend 222 with the
lower opposing primary bend 222' includes a secondary bend 226a and
the strut 224b connecting the primary bend 222 with the upper
opposing primary bend 222' includes a secondary bend 226b.
[0058] The primary bend 222 in the embodiment of FIG. 6 and the
portions of the struts 224a and 224b located between the secondary
bends 126a and 126b and the primary bend 222 form a generally
circular element as seen in FIG. 6. As described with respect to
the embodiments of FIGS. 3 and 5 above, however, it is preferred
that the struts 224a and 224b abut first at the apexes 227a and
227b formed by the secondary bends 226a and 226b during compression
to thereby reduce the maximum bending stresses associated with
compression of the stent.
[0059] Yet another alternative construction is depicted in FIG. 7
and includes a primary bend 322 on one end of a support section and
two opposing primary bends 322' on the opposing end of the support
section. The strut 324a connecting the primary bend 322 with the
lower opposing primary bend 322' includes a protrusion 327a facing
the opposing strut 324b attached to the primary bend 322.
Similarly, the strut 324b connecting the primary bend 322 with the
upper opposing primary bend 322' includes a protrusion 327b facing
the opposing strut 324a.
[0060] Although the struts 324a and 324b do not include secondary
bends as in those struts described above, the protrusions 327a and
327b define the point at which the struts 324a/324b first abut when
the stent is compressed. Because that point is removed from the
primary bend 322, the minimum bending radius of the primary bend is
limited, thereby reducing the maximum bending stresses at the
primary bends that is associated with compression of the stent.
[0061] FIG. 8 illustrates yet another feature of stents according
to the present invention when compared to the stent depicted in
FIG. 2. The view of FIG. 8 is a portion of a stent body including
two adjacent support sections 420a and 420b. Support section 420a
includes primary bends 422a on one end and opposing primary bends
422a' on the opposite end of the support section 420a. Similarly,
the support section 420b includes primary bends 422b on one end of
the support section 420b and opposing primary bends 422b' on the
opposite end of the support section 420b.
[0062] In the embodiment depicted in FIG. 8, the primary bends 422a
and 422b in adjacent support sections 420a and 420b are generally
aligned along the longitudinal axis 414. Likewise, the primary
bends 422a' and 422b' in adjacent support sections 420a and 420b
are also generally aligned along the longitudinal axis 414. As a
result, the support sections 420a and 420b are said to be "in
phase" with each other.
[0063] FIG. 2 illustrates a stent in which the support sections 20
are "out of phase" with the adjacent support sections because the
primary bends 22 and 22' on the adjacent support sections 20 do not
generally align along the longitudinal axis 14 as do the primary
bends 422a/422b and 422a'/422b' in the embodiment depicted in FIG.
8.
[0064] The radially expandable stents depicted and described above
with respect to FIGS. 1-8 are preferably formed as a one-piece,
completely integral units from a thin-walled tube of suitable
material. Typically, the stents will be cut or machined from a tube
using, e.g., laser, water jet, EDM (electrical discharge
machining), or chemical etching techniques. As a result, the stents
can be formed without welds or joints. It is also envisioned,
however, that stents according to the present invention could be
formed from a sheet of material using, e.g., laser, water jet, EDM,
or chemical etching techniques. If the stent was formed from a
sheet of material, the body 10 as seen in FIG. 2 would be formed
into a tube and welded or otherwise joined along one side of the
stent resulting in a series of welds or other joints along the
length of the body.
[0065] Preferred materials for stents according to the present
invention include those materials that can provide the desired
functional characteristics with respect to biological
compatibility, modulus of elasticity, etc. For example, it is
preferred that the stents be biologically compatible, as well as be
capable of significant recoverable strain to assume a low profile
for delivery to a desired location within a body lumen. After
release of the compressed stent, it is preferred that the stent be
capable of radially expanding back to its original diameter.
[0066] Particularly preferred materials for stents according to the
present invention are nickel titanium alloys and other alloys that
exhibit superelastic behavior, i.e., are capable of significant
distortion without plastic deformation. Stents manufactured of such
materials can be significantly compressed without plastic
deformation, i.e., they are compressed such that the maximum strain
level in the stent is below the recoverable strain limit of the
material. Discussions relating to nickel titanium alloys and other
alloys that exhibit behaviors suitable for stents according to the
present invention can be found in, e.g., U.S. Pat. No. 5,597,378
(Jervis) and WO 95/31945 (Burmeister et al.). Nickel titanium
alloys suitable for use in manufacturing stents according to the
present invention can be obtained from, e.g., Memry Corp.,
Brookfield, Conn.
[0067] The radially outward directed force developed by the stents
according to the present invention serves two functions. One
function is to hold the body lumen open against a force directed
radially inward, e.g., a spasm, as well as preventing restriction
of the passageway through the lumen by intimal flaps or dissections
generated by, e.g., prior balloon angioplasty. Another function is
to fix the position of the stent within the body lumen by intimate
contact between the stent and the walls of the lumen. The outwardly
directed forces must not be excessive, however, to avoid
traumatization of the lumen walls by the stent.
[0068] The diameters of some preferred stents when in the
compressed state for delivery to a desired location within a body
lumen is typically reduced from about two to about six times the
diameter of the stents when in their expanded state before
compression. For example, typical stents may have a compressed
external diameter of about 1 millimeter to about 3 millimeters for
delivery and an expanded external diameter in a body lumen of about
3 millimeters to about 15 millimeters when released from
compression in a large arterial vessel. Some preferred stents used
in coronary arteries may have a compressed external diameter of
about 1 millimeter and an expanded external diameter in a body
lumen of up to about 5 millimeters.
[0069] In addition to ranges in diameters, it will also be
understood that the stents according to the present invention can
have any desired longitudinal length as required for a particular
application. Furthermore, although the illustrative stents depicted
in FIGS. 1-8 have a plurality of successive support sections, it
will be understood that some stents according to the present
invention could be manufactured with only one support section (in
which case no longitudinal members would be required to connect
adjacent support sections).
[0070] Having thus described radially expandable stents according
to the present invention, we will now describe one delivery system
suitable for deploying the self-expanding stents described above as
well as other radially expandable stents. The delivery system
depicted in FIGS. 9-11 provides for delivery of a stent to a
desired location within a body lumen. It will be understood that
the stents described above may be deployed by any suitable delivery
system and they are not to be limited to deployment by the delivery
systems described below.
[0071] The delivery system of FIG. 9 includes a handle 50 at the
proximal end. The handle 50 includes a release button 51 that
slides within a channel 52 located in the handle 50. Preferably,
the release button 51 is actuated by a user's thumb to assist in
one-handed delivery of the stent as discussed in more detail
below.
[0072] It is preferred that the release button 51 be locked or
retained in position before delivery to prevent accidental or
unwanted deployment of the stent from the delivery system. One
preferred retaining mechanism is a bend or turn in the distal end
of the channel 52 such that the channel 52 includes a
circumferential portion at the distal end connecting to the
otherwise longitudinal channel 52 seen in FIG. 9. The retaining the
release button 51 in position at the distal end of the channel 52
(in the circumferential portion of the channel) until delivery of
the stent is desired, at which time the button is moved
circumferentially and then longitudinally along the length of the
channel 52 to release the stent as discussed in more detail
below.
[0073] Those skilled in the art will understand that a variety of
retaining mechanisms could be substituted for the preferred
mechanism described above. Examples of suitable alternatives
include, but are not limited to: a removable security band around
the handle 50 that must be removed to move the release button 51
proximally, stoppers within the channel 52 that must be removed to
move the release button 51 proximally, a detent mechanism in which
the release button can be depressed radially inward to release the
button 51 for movement within the channel, etc.
[0074] A support tube 54 extends from the distal end of the handle
50 and preferably extends into the hemostasis valve 94 of the
Y-connector 92 of a guide catheter 90. Preferably, the support tube
54 terminates within the guide catheter 90 at a point near the
Y-connector 92. The guide catheter 90 preferably terminates at a
distal end 96 spaced from the Y-connector 92. The construction of
guide catheters, Y-connectors and hemostasis valves are well known
and will not be described further.
[0075] FIG. 10 is a cross-sectional view of the proximal portion of
the delivery system taken along the longitudinal axis of the
support tube 54 as indicated by line 1010 in FIG. 9. The support
tube 54 is coaxial with a cover sheath 70 and inner tube 60, both
of which are described in more detail below. It is preferred that
the cover sheath 70 be movable within the support tube 54 and that
the cover sheath 70 also be movable relative to the inner tube 60.
Further, it is preferred that the inner tube 60 and the support
tube 54 be fixed relative to each other.
[0076] FIG. 11 is an enlarged view of the distal portion of the
delivery device in which the stent 10 is located within the lumen
72 formed by the cover sheath 70. The cover sheath 70 maintains the
stent 10 in a compressed state in which the stent 10 has a diameter
suitable for delivery to an internal body lumen 100. Because the
stent 10 is self-expanding, it is biased radially outward against
the interior surface of the cover sheath 70 as depicted.
[0077] An inner tube 60 preferably extends through the cover sheath
70 and the compressed stent 10 as seen in FIG. 11. The inner tube
60 also preferably includes a guidewire lumen 64 extending through
to the distal end 61 of the inner tube 60. For clarity, the
guidewire 104 has been removed from the guidewire lumen 64 in the
inner tube 60 of FIG. 11.
[0078] The preferred inner tube 60 includes a shoulder 62 proximal
to the proximal end 16 of the stent 10. The shoulder 62 prevents
the stent 10 from moving proximally with the cover sheath 70 during
deployment because the outside diameter of the inner tube 60 at the
shoulder 62 is greater than the inside diameter of the compressed
stent 10. As a result, the position of the stent 10 relative to the
shoulder 62 on inner tube 60 is fixed when the cover sheath 70 is
moved proximally during deployment of the stent 10 as described
below.
[0079] Inner tube 60 preferably extends to the handle 50 of the
delivery system depicted in FIG. 9. Furthermore, the inner tube 60
is preferably fixedly attached to the handle 50 and is
substantially inextensible along its length. As a result, the
distance between the handle 50 and the shoulder 62 on the inner
tube 60 is fixed. Because the distance between the shoulder 62 and
the handle. 50 is fixed, the distance between the handle 50 and the
compressed stent 10 on the interior surface of the cover sheath 70
is also fixed during deployment.
[0080] The stent 10 is released by moving the cover sheath 70
towards the proximal end of the delivery device, i.e., away from
the distal end 61 of the inner tube 60. The cover sheath 70 is
connected to an actuator such as a release button 51 on the handle
50 such that movement of the button 51 towards the proximal end 53
of the handle 50 moves the cover sheath 70 in the proximal
direction towards the handle 50. If the stent 10 is self-expanding,
that movement of the cover sheath 70 preferably removes the
constraining forces on the compressed stent 10, thereby allowing it
to expand within the lumen 100. Actuators that accomplish the
function of moving the cover sheath 70 relative to the handle 50
other than the preferred release button 51 will be known to those
skilled in the art.
[0081] To assist in positioning the stent 10 during delivery, it is
preferred that one radio-opaque marker 68 be provided on the inner
tube 60 at the proximal end 16 of the stent 10 and another
radio-opaque marker 74 be provided on the cover sheath 70 at the
distal end 18 of the stent 10. Movement of the marker 74 on the
cover sheath 70 past the marker 68 on the inner tube 60 is
preferably indicative of sufficient movement of the cover sheath 70
such that the stent 10 is no longer constrained by within the lumen
72 of the cover sheath has been deployed within the body lumen
100.
[0082] FIG. 12 is an enlarged view of the distal portion of an
alternative delivery system incorporating an inflatable balloon 180
on the inner tube 160, with the balloon preferably located within
the passageway formed by the compressed stent 110. As described in
connection with the embodiment depicted in FIG. 11, the stent 110
is located within the lumen 172 formed by the cover sheath 170. The
cover sheath 170 maintains the stent 110 in a compressed state in
which the stent 110 has a diameter suitable for delivery to an
internal body lumen. Because the stent 110 is self-expanding, it is
biased radially outward against the interior surface of the cover
sheath as depicted.
[0083] The inner tube 160 also preferably includes a guidewire
lumen 164 extending through to the distal end 161 of the inner tube
160. The inner tube 160 also includes a shoulder 162 at the
proximal end 116 of the stent 110 to assist in deploying the stent
110 as described above in connection with FIG. 11. Inner tube 160
also preferably extends to the handle of a delivery system as
described above in connection with FIG. 11.
[0084] As seen in FIG. 12, the portion of the inner tube 160 on
which the balloon 180 is mounted preferably has a reduced diameter
to maintain a low profile while allowing room for the balloon 180.
The inner tube 160 also includes an inflation lumen 182 in fluid
communication with the interior of the collapsed balloon 180. The
inflation lumen 182 is used to deliver the fluids used to inflate
the balloon 180 during deployment of the stent 110. The inflation
lumen 182 preferably terminates at the proximal end of the inner
tube 160 where the fluid source can be connected by known
methods.
[0085] To assist in positioning the stent 110 during delivery, it
is preferred that one radio-opaque marker 168 be provided on the
inner tube 160 at the proximal end 116 of the stent 110 and another
radio-opaque marker 174 be provided on the cover sheath 170 at the
distal end 118 of the stent 110. Movement of the marker 174 on the
cover sheath 170 past the marker 168 on the inner tube 160 is
preferably indicative of sufficient movement of the cover sheath
170 such that the stent 110 is no longer constrained by within the
lumen 172 of the cover sheath has been deployed within a body
lumen.
[0086] As described above in connection with FIG. 9, the preferred
delivery systems according to the present invention also preferably
include a support tube 54 exterior to and coaxial with the cover
sheath 70 and inner tube 60 to further assist in accurate placement
of the stent 10. The support tube 54 preferably extends from the
handle 50 and is sufficiently long to extend into the lumen of the
guide catheter 90. As best seen in FIG. 9, the support tube 54
preferably extends into, e.g., a Y-connector 92 of the guide
catheter 90 such that the position of the support tube 54 can be
fixed relative to the guide catheter 90 by closure of the
hemostasis valve 94 on the Y-connector 92.
[0087] It is preferred that the support tube 54 be fixedly attached
to the handle 50 and that the support tube 54 be substantially
inextensible along its longitudinal axis such that, after the
support tube 54 is fixed in the hemostasis valve 94, the handle 50
is located a fixed distance from the hemostasis valve 94. The cover
sheath 70 located within the support tube 54 (see FIG. 10) is,
however, free to move longitudinally within the support tube 54
during deployment of the stent 10. Because the support tube 54 and
the inner tube 60 are both fixedly attached to the handle 50,
however, the distance between the stent 10 and the hemostasis valve
94 (and handle 50) are also fixed on closure of the hemostasis
valve 94 on the support tube 54.
[0088] Use of the delivery system described above will now be
described in connection with balloon angioplasty treatment of a
lesion within a coronary vessel. Deployment of the stent will
typically involve balloon angioplasty to expand the passageway
through a lesion. Typically, a balloon catheter will be advanced
over a guidewire to the desired location. After dilatation, the
balloon catheter will be withdrawn while the guidewire 104 and
guide catheter 90 used with the balloon catheter remain in
position. The guide catheter 90 is typically sutured in position to
fix its location relative to the patient. At that point, the inner
tube 60 and cover sheath 70 with compressed stent 10 will be
advanced through the guide catheter 90 past the distal end 96 of
the guide catheter 90 along the guidewire 104 until the stent 10 is
in the desired location relative to the lesion 102. That position
can be verified by, e.g., using the radio-opaque markers 68 and 74
on the inner tube 60 and cover sheath 70 as described above.
[0089] With the stent 10 in the desired location, the hemostasis
valve 94 is preferably fastened or closed on the support tube 54,
thereby fixing the position of the stent relative to the guide
catheter 90 (which, in turn fixes the position of the stent 10
relative to the patient because of the connection between the guide
catheter 90 and the patient as described above). With the
hemostasis valve 94 closed, the release button 51 is moved from its
locked position within the channel 52 and then gently moved towards
the proximal end 53 of the handle 50. That movement preferably
draws the distal end 76 of the cover sheath 70 past the stent 10.
If the stent 10 is self-expanding, it will typically expand
radially outward from the inner tube 60 towards the interior
surface of the lesion 102.
[0090] After the cover sheath 70 is withdrawn sufficiently to
expose the stent 10, the balloon 80 can be inflated to either
expand the stent 10 (if it is not self-expanding) or to assist in
proper seating of the stent 10 against the interior surface of the
lumen 100 and/or lesion 102. The balloon 80 is preferably a high
pressure balloon (operating at 12-14 Bars) and preferably has an
inflated diameter that is less than or equal to the interior
diameter of the stent 10 as expanded.
[0091] Another feature of one preferred rapid-exchange delivery
system according to the present invention is in the routing of the
guidewire 104 out of the inner tube 60 and cover sheath 70 at a
point between the distal end 61 of the inner tube 60 and the distal
end of the support tube 54. Turning to FIG. 13, a portion of a
rapid-exchange delivery system proximal from the distal end 61 of
the inner tube 60 is depicted which includes the cover sheath 70
and the inner tube 60 located within the lumen 72 of the cover
sheath 70. The guidewire lumen 64 of the inner tube 60 terminates
in a first guidewire opening 63 in the depicted embodiment. A
second guidewire opening 73 is provided in the cover sheath 70.
[0092] A guide element 130 is preferably provided that extends
through the second guidewire opening 73 and the first guidewire
opening 63 and into the guidewire lumen 64 of the inner tube 60. As
such, advancement of the proximal end 106 of the guidewire 104
towards the proximal end of the delivery system through the
guidewire lumen 64 (to the left in FIG. 13) moves the proximal end
106 of the guidewire 104 into a lumen 132 in the guide element
130.
[0093] It is preferred that only a portion of the guidewire 104 fit
within the lumen 132 in the guide element 130. As a result,
continued advancement of the guidewire 104 towards the proximal end
of the delivery system forces the guide element 130 out of the
first and second guidewire openings 63/73 as well as guides the
proximal end 106 of the guidewire 104 through those openings. After
the proximal end 106 of the guidewire 104 is threaded through the
openings 63/73 in the inner tube 60 and cover sheath 70, the distal
portion of the inner tube 60 and cover sheath 70 in which the
guidewire 104 is contained can be advanced through the guide
catheter 90 along the guidewire 104.
[0094] Although FIG. 13 illustrates one embodiment of a
rapid-exchange delivery system, it will be understood that the
stents according to the present invention can be delivered by any
delivery system, e.g., an over-the-wire delivery system or by any
other suitable delivery system. Furthermore, it will also be
understood that the distal portions of the delivery system as
depicted in FIGS. 11 and 12 could be used in connection with any
suitable delivery system, including, e.g., rapid-exchange or
over-the-wire delivery systems.
[0095] Furthermore, the preceding specific embodiments are
illustrative of the practice of the invention. It is to be
understood, however, that other expedients known to those skilled
in the art or disclosed herein, may be employed without departing
from the scope of the appended claims.
* * * * *