Title: Apparatus for delivering endoluminal prostheses and methods of making and using them
Abstract: An apparatus for delivering a stent into a blood vessel includes a sheath having a rounded bullet-shaped distal portion including a plurality of flexible leaflets integrally molded thereto. The stent is disposed in its contracted condition within a lumen of the sheath proximate the distal portion. A bumper is slidably disposed within the lumen that includes a helical compression coil, a bumper element attached to the helical coil including a blunt distal edge for abutting the stent, and an extension element extending distally from the bumper element through the stent and between the leaflets to facilitate introducing the apparatus over a guidewire. The sheath is formed by inserting a bullet into a blunt-ended tube, and inserting the tube into a bullet-shaped bore in a heated die until the tube material is softened and deforms into a rounded bullet shape. Slits are then cut into the distal portion to create the leaflets.
Patent Number: 6,945,989 Issued on 09/20/2005 to Betelia, et al.
| Inventors:
|
Betelia; Rainier (San Jose, CA);
Gillis; Edward M (Cupertino, CA);
Rourke; Jonathan M. (Los Altos, CA);
Yang; Yi (San Francisco, CA)
|
| Assignee:
|
Endotex Interventional Systems, Inc. (Cupertino, CA)
|
| Appl. No.:
|
664970 |
| Filed:
|
September 18, 2000 |
| Current U.S. Class: |
623/1.11 |
| Intern'l Class: |
A61F 002/06 |
| Field of Search: |
623/111,112,123,12,118,134,119
606/108,194
|
References Cited [Referenced By]
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Other References
EPO Publication No. EP O 873 733 A1, "Controllable Stent Delivery System", Oct.
28, 1998.
EPO Publication No. EP O 876 804 A1, "Passive Perfuson Stent Delivery System",
Nov. 11, 1998.
PCT Publication No. WO 99/48908, "A Delivery Catheter", Oct. 7, 1999.
|
Primary Examiner: Ho; (Jackie) Tan-Uyen T.
Attorney, Agent or Firm: Orrick Herrington & Sutcliffe, LLP
Claims
1. An apparatus for delivering a prosthesis into a blood vessel of a patient, comprising:
an elongate tubular member having a proximal end, a distal end, and a lumen extending
between the proximal and distal ends, the distal end having a size for endoluminal
insertion into a blood vessel and terminating in a substantially atraumatic distal
portion comprising a plurality of flexible leaflets integrally molded thereto,
the leaflets being deflectable from a closed position wherein the leaflets engage
one another to an open position wherein the leaflets define an opening communicating
with the lumen;
a tubular prosthesis disposed within the lumen proximate the distal portion; and
an elongate bumper member having a proximal end and a distal end, the bumper
member being slidably disposed within the lumen of the elongate tubular member,
the distal end of the bumper member having a blunt edge that engages the proximal
end of the prosthesis for preventing axial displacement of the prosthesis upon
retraction of the tubular member with respect to the bumper member;
wherein the bumper member comprises a helical coil.
2. An apparatus for delivering a prosthesis into a blood vessel of a patient, comprising:
an elongate tubular member having a proximal end, a distal end, and a lumen extending
between the proximal and distal ends, the distal end having a size for endoluminal
insertion into a blood vessel;
a tubular prosthesis disposed within the lumen proximate the distal end; and
an elongate bumper member comprising a helical coil having a proximal end and
a distal end, the bumper member being slidably disposed within the lumen of the
elongate tubular member, the distal end of the bumper member having a blunt distal
edge that engages the proximal end of the prosthesis for preventing axial displacement
of the prosthesis upon retraction of the tubular member with respect to the bumper member.
3. The apparatus of claim 2, wherein the tubular member comprises a substantially
atraumatic distal portion comprising a plurality of flexible leaflets integrally
molded thereto, the leaflets being deflectable from a closed position wherein the
leaflets engage one another to an open position wherein the leaflets define an
opening communicating with the lumen.
4. The apparatus of claim 3, wherein the leaflets define a substantially rounded
bullet shape in the closed position.
5. The apparatus of claim 3, wherein the leaflets are substantially flexible
and independently deflectable at a temperature less than body temperature.
6. The apparatus of claim 3, wherein the leaflets are biased towards the closed
position, but are resiliently deflectable to the open position.
7. The apparatus of claim 2, wherein adjacent leaflets are connected to one another
by weakened regions, the weakened regions being tearable upon retraction of the
tubular member with respect to the prosthesis to allow the leaflets to be deflected
toward the open position.
8. The apparatus of claim 3, wherein the leaflets include a portion having a
thickness that is substantially thinner than a wall thickness of the distal portion
of the tubular member from which the leaflets extend.
9. The apparatus of claim 2, wherein the bumper member comprises a helical wire
compression coil extending between its proximal and distal ends.
10. The apparatus of claim 2, wherein the bumper member comprises a plastic bumper
element extending from a distal end of the helical coil, the bumper element including
the blunt distal edge thereon.
11. The apparatus of claim 10, wherein the bumper member further comprises an
extension element extending from the bumper element, the extension element having
a cross-section substantially smaller than the bumper element, whereby the extension
element may extend through the prosthesis disposed within the lumen of the tubular member.
12. The apparatus of claim 11, wherein the extension element comprises a lumen
for receiving a guidewire therethrough.
13. The apparatus of claim 2, further comprising a radiopaque marker on the distal
end of the bumper member.
Description
FIELD OF THE INVENTION
The present invention relates generally to apparatus and methods for delivering
endoluminal prostheses within body lumens of a patient, and more particularly to
apparatus for delivering tubular prostheses or "stents" within a patient's vasculature
for treating stenoses or other lesions, for example, within the coronary and carotid
arteries, and to methods of making and using such apparatus.
BACKGROUND
In recent years, a number of minimally invasive technologies have been developed
for treating diseases, such as atherosclerosis, that result in narrowing of blood
vessels, for example, within the coronary or carotid arteries. Tubular prostheses
or "stents" have been developed for maintaining the patency of a blood vessel,
for example, following angioplasty or other procedures used to treat a stenosis,
occlusion, or other lesion within the blood vessel. The stent may be implanted
across a treatment site to scaffold the site and prevent it from subsequently contracting
or otherwise becoming obstructed.
Generally, the stent may be placed upon a catheter in a contracted condition,
and the catheter advanced endoluminally to the treatment site until the stent is
positioned across the stenosis. The stent may then be deployed and substantially
anchored at the treatment site. The stent may be self-expanding, i.e., may be biased
to expand to an enlarged condition upon release from the delivery catheter, thereby
automatically substantially anchoring the stent at the treatment site. Alternatively,
the stent may be plastically deformable, i.e., may be expanded with the aid of
a balloon, which may underlie the stent on the catheter. The balloon may be inflated
to expand the stent from the contracted condition to the enlarged condition wherein
the stent substantially engages the wall of the treatment site. A balloon, for
example, on a separate balloon catheter, may also be used to further expand and/or
anchor a self-expanding stent.
Similarly, for ablation procedures and the like, a catheter including
an array of electrodes, for example, on an expandable basket assembly, may be provided.
The device may be introduced into a body lumen, e.g., through the patient's vasculature
into the heart, to treat conditions, such as heart arrhythmia.
With any of these devices, a sheath may be provided over the catheter to protect
the elements on the distal end of the catheter, such as a stent, a balloon, and/or
an array of electrodes. The sheath may be advanced distally over the proximal end
of the catheter until it covers the distal end and the element(s) thereon, or the
distal end of the catheter may be introduced into the sheath, and advanced until
it is proximate the distal end of the sheath. The distal end of the catheter, with
the overlying sheath thereon, may then be introduced into a patient and positioned
at a treatment site, whereupon the sheath may be retracted to expose the distal
end of the catheter. After treatment, the sheath may be advanced back over the
distal end of the catheter, and the entire device withdrawn from the patient.
One of the problems associated with these devices is that they may have substantially
blunt distal ends that may scrape along the wall of a vessel during advancement
therethrough, possibly damaging the wall and/or dislodging embolic material from
the wall. To facilitate atraumatic advancement, particularly through tortuous anatomy,
transition tips have been suggested for these devices.
For example, a conical or tapered nosepiece may be provided on the distal end
of the catheter. A sheath may be disposed over the catheter, for example, to substantially
cover the stent or other underlying element, such that the nosepiece extends distally
from the end of the sheath, a distal edge of the sheath abutting the nosepiece.
The nosepiece may facilitate advancement of the device through a narrow region
of a blood vessel, although it may also risk catching on the wall of the vessel
and/or dislodging embolic material, e.g., between the distal edge of the sheath
and the nosepiece. Following delivery of a stent from the device, the nosepiece
is generally positioned distal to the treated lesion. If the nosepiece is withdrawn
directly, the proximal edge of the nosepiece may catch on the stent struts, resulting
in the potential for trauma and embolic debris release. Alternatively, the sheath
may be re-advanced across the treatment site to "recapture" the nosepiece, although
in this approach the distal edge of the sheath may also catch on the stent struts.
As an alternative to a tapered nosepiece, a sheath having a rounded distal end
has been suggested, as disclosed in U.S. Pat. No. 5,593,412 issued to Martinez
et al. Weakened areas or slits are provided in the distal end, thereby defining
sections that may be softened upon introduction of warm saline solution. Once the
sections are softened, the sheath may be retracted from an underlying balloon catheter
to expose and implant a stent mounted on the catheter. Introduction of saline or
other liquids into a patient's vasculature, however, may be undesirable, but is
necessary in order to soften the sections on the distal end of the sheath and allow
the stent to be deployed from the sheath.
Another problem associated with such delivery systems is that the sheaths
and/or catheters may buckle during insertion, because of the distal force applied
from the proximal end to advance them through the patient's vasculature. In addition,
because of their tubular nature, they may kink when advanced through tortuous anatomy,
possibly damaging the device or an element within the device.
Accordingly, it is believed that delivery systems that facilitate delivery
of a stent through a patient's vasculature and/or that overcome the problems discussed
above would be considered useful.
SUMMARY OF THE INVENTION
The present invention is directed to apparatus for delivering treatment elements,
such as tubular prostheses or "stents," within a body lumen of a patient, for example,
for treating stenoses or other lesions within the coronary arteries, the carotid
arteries, or other blood vessels, and to methods of making and using such apparatus.
In accordance with one aspect of the present invention, an apparatus is provided
for delivering a prosthesis into a blood vessel of a patient that includes an elongate
tubular member having a proximal end, a distal end, and a lumen extending between
the proximal and distal ends. The distal end has a size for endoluminal insertion
into a blood vessel and terminates in a substantially atraumatic distal portion
including a plurality of flexible leaflets integrally molded thereto.
The leaflets are deflectable from a closed position wherein the leaflets engage
one another to an open position wherein the leaflets define an opening communicating
with the lumen. Preferably, the leaflets define a substantially rounded bullet
shape in the closed position, although alternatively, the leaflets may define a
substantially conical shape in the closed position. The leaflets are preferably
substantially flexible and independently deflectable at a temperature less than
body temperature, and are biased towards the closed position, but are resiliently
deflectable to the open position. Adjacent leaflets may be separated by a slit,
or may be connected to one another by weakened regions, the weakened regions being
tearable upon retraction of the tubular member with respect to the prosthesis to
allow the leaflets to be deflected towards the open position.
In a preferred embodiment, a tubular prosthesis is disposed within the lumen
proximate
the distal portion. An elongate bumper member having a proximal end and a distal
end is also provided, the bumper member being slidably disposed within the lumen
of the sheath. The distal end of the bumper member has a blunt edge disposed adjacent
to the proximal end of the prosthesis for preventing axial displacement of the
prosthesis upon retraction of the tubular member with respect to the bumper member
and/or the prosthesis.
Preferably, the prosthesis comprises a self-expanding stent, such as
a coiled-sheet stent, the stent being biased to assume an expanded condition having
a cross-section larger than the lumen of the tubular member, and being compressible
to a contracted condition to facilitate insertion into the lumen.
In accordance with another aspect of the present invention, an apparatus for
delivering
a prosthesis into a blood vessel of a patient is provided that includes an elongate
tubular member, such as that described above, having a proximal end, a distal end,
and a lumen extending between the proximal and distal ends, the distal end having
a size for endoluminal insertion into a blood vessel. A tubular prosthesis is disposed
within the lumen proximate the distal end. An elongate bumper member is also provided
that includes a helical coil having a proximal end and a distal end, the bumper
member being slidably disposed within the lumen of the sheath. The distal end of
the bumper member has a blunt distal edge disposed adjacent a proximal end of the
prosthesis for preventing axial displacement of the prosthesis upon retraction
of the tubular member with respect to the bumper member.
In a preferred embodiment, the bumper member includes a helical wire compression
coil, preferably a solid height coil, extending between its proximal and distal
ends. A plastic bumper element extends from a distal end of the helical coil, the
bumper element including the blunt distal edge thereon. An extension element extends
distally from the bumper element, the extension element having a cross-section
substantially smaller than the bumper element, whereby the extension element may
extend through the prosthesis disposed within the lumen of the tubular member.
The helical coil, bumper element, and/or the extension element include a lumen
extending axially therethrough for receiving a guidewire therethrough.
In accordance with yet another aspect of the present invention, a method for
making
a sheath for delivering a treatment element within a body lumen of a patient is
provided. A tubular member is provided that is formed from a substantially flexible
material, the tubular member having a proximal end, a distal end, and a lumen extending
axially between the proximal and distal ends, the distal end having a size for
endoluminal insertion into a body lumen. A die is provided having a bore therein,
the bore having a tapered shape. The die is heated to a temperature in excess of
a melting point of the flexible material from which the tubular member is formed.
The distal end of the tubular member is inserted into the bore of the heated die
until a distal portion of the tubular member is softened and deformed into a tapered
shape substantially enclosing the distal end. One or more slits are then created
in the distal portion of the tubular member after it is deformed into the tapered
shape, the slits defining a plurality of leaflets. A treatment element may be inserted
into the lumen of the tubular member until it is disposed proximate the distal portion.
In a preferred method, a bullet having a tapered shape distal end is inserted
into the distal end of the tubular member before inserting the distal end of the
tubular member into the bore. Preferably, the bullet and the bore have corresponding
substantially rounded shapes defining a mold cavity therebetween when the distal
end of the tubular member is inserted into the bore.
In another preferred method, the treatment element is a tubular prosthesis for
implantation within a body lumen of a patient. Preferably, the prosthesis is a
self-expanding stent biased to assume an expanded condition having a cross-section
larger than the lumen, and compressible to a contracted condition before being
inserted into the lumen of the tubular member. The prosthesis may be inserted into
the lumen of the tubular member before inserting the distal end of the tubular
member into the bore, e.g., inserted into the lumen from the distal end of the
tubular membrane. Alternatively, the prosthesis may be inserted into the lumen
from the proximal end of the tubular member, e.g., either before or after the leaflets
are formed on the distal portion of the tubular member.
An elongate bumper member may be inserted into the lumen of the tubular member,
the bumper member being slidably disposed within the lumen of the tubular member,
the distal end having a blunt distal edge for abutting a proximal end of the prosthesis.
To make the bumper member, an elongate helical coil may be provided having a proximal
end and a distal end. A tubular bumper element may be attached to the distal end
of the helical coil to provide the bumper member, the bumper element including
the blunt distal edge of the bumper element. Preferably, the bumper element is
formed from plastic, and is attached to the helical coil by heating the bumper
element until it is softened, and then directing the softened bumper element over
the distal end of the helical coil. A tubular extension element may be attached
to the bumper element, the extension element having a cross-section substantially
smaller than the bumper element.
Other objects and features of the present invention will become apparent from
consideration of the following description taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A is a cross-sectional side view of a sheath having a rounded distal tip,
in accordance with the present invention.
FIG. 1B is a cross-sectional side view of an apparatus for delivering a stent,
including the sheath of FIG. 1A.
FIGS. 2A and 2B are end views of the sheath of FIGS. 1A and 1B, respectively.
FIGS. 3A-3E are cross-sectional views showing a method for forming a rounded
distal tip on a sheath, such as that shown in FIG. 1A.
FIGS. 4A and 4B are cross-sectional views of a body lumen, showing a method
for implanting a stent using an apparatus in accordance with the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Turning now to the drawings, FIGS. 1A-2B show a preferred embodiment of an
apparatus
10 for delivering a stent or other tubular prosthesis
50
into a blood vessel or other body lumen of a patient (not shown). Generally, the
apparatus
10 includes an elongate tubular sheath
12 having a proximal
end (not shown), a distal end
14, and a lumen
16 extending generally
therebetween. The tubular sheath
12 may be formed from a substantially flexible
or semi-rigid material that may facilitate its advancement within a body lumen
of a patient, preferably within the vasculature of a patient.
For example, the sheath
12 may be formed from a polymer, such as pebax,
polyethylene, urethane, nylon, or other plastic material, that may be extruded
or molded into elongate tubing of a desired length. Preferably, the tubing has
a wall thickness of between about 0.003-0.006 inch (0.075-0.150 mm), and has a
substantially uniform outer diameter appropriate for the size of the stent being
implanted, for example, between about 1.5-2.5 mm. The sheath
12 may have
a substantially uniform construction along its length, or the sheath
12
may include portions along its length having varying degrees of flexibility.
In a preferred embodiment, the sheath
12 includes a distal portion
18
formed entirely from a substantially flexible material, such as pebax, and an intermediate
portion
20 formed from pebax including a stiffening element
22 therein.
For for example, the intermediate portion
20 may include a braid or mesh,
e.g., of stainless steel, laid over a teflon liner, with pebax tubing formed over
the braid. Alternatively, the stiffening element
22 may be a helical wire
coil and the like molded or otherwise formed in the tubing. The stiffening element
22 may enhance a rigidity of the intermediate portion
20, for example,
to reduce the risk of the intermediate portion
20 buckling or kinking, while
still providing flexibility transverse to the longitudinal axis
28, e.g.,
to accommodate advancement through tortuous anatomy. Preferably, the sheath
12
also includes a proximal portion (not shown) that is formed from a more rigid material,
such as nylon tubing, that may include a stiffening element as described above.
In a preferred embodiment, the distal portion
18 has a length of between
about 10-20 cm, the intermediate portion
20 has a length of between about
20-30 cm, and the proximal portion has a length of between about 85-120 cm, more
preferably about 100 cm or more.
The distal portion
18 of the sheath
12 preferably has a rounded
bullet shape defined by a plurality of flexible leaflets
24 that are integrally
formed thereon. The leaflets
24 are preferably deflectable from a closed
position, wherein adjacent leaflets
24 abut one another, to an open position.
In the closed position, the leaflets
24 substantially close the lumen
16,
as shown in FIG. 2A. Preferably, in the closed position, the leaflets
24
define a relatively small opening
25 where their apices meet. In the open
position (the leaflets
24 are shown only partially open in FIG. 2B), the
leaflets
24 are spread apart to define an opening
26 communicating
with the lumen
16. Preferably, in the open position, the leaflets
24
are oriented substantially axially such that the opening
26 has a cross-section
similar to the lumen
16. In the preferred embodiment shown in FIGS. 2A and
2B, three leaflets
24 are provided, although additional leaflets may be
provided if desired.
As best seen in FIG. 1A, in the closed position, the leaflets
24 preferably
define a substantially atraumatic distal portion
18 that may facilitate
advancement of the sheath
12 endoluminally within a patient's vasculature
with minimal risk of dislodging embolic material from and/or otherwise damaging
the wall of a body lumen through which the sheath
12 is advanced. In the
preferred embodiment shown, the leaflets
24 define a substantially rounded
bullet shape in the closed position. Alternatively, leaflets
24 defining
a substantially conical shape (not shown) in the closed position may be provided,
with the leaflets
24 preferably biased to the closed position, as described below.
The leaflets
24 are substantially flexible and independently deflectable
substantially independent of the temperature to which the leaflets
24 are
exposed, e.g., at a temperature substantially less than body temperature. In a
preferred embodiment, the leaflets
24 are biased towards the closed position,
but are resiliently deflectable to the open position. This may ensure that the
opening
26 remains substantially closed until time of deployment of an element,
such as stent
50, from within the lumen
16, and/or that the leaflets
24 do not catch on anything and open inadvertently. This may be particularly
important when the apparatus
10 is advanced through tortuous anatomy, as
described further below. Alternatively, the leaflets
24 may be at least
partially plastically deformed when they are deflected from the closed position
to the open position. In this alternative, the leaflets
24 may not return
completely to the closed position when released from the fully open position, e.g.,
after the stent
50 is deployed from the apparatus
10.
Preferably, adjacent leaflets
24 are separated by a relatively
narrow slit
28, although alternatively, the leaflets
24 may partially
overlap with one another in the closed position. In a further alternative, adjacent
leaflets may be separated by a thin-walled or weakened region (not shown) that
may be easily tearable upon retraction of the sheath
12 with respect to
a stent or other element being deployed from within the lumen
16. Once the
weakened regions are torn, the leaflets may be freely deflected towards the open
position as the element is being deployed.
In addition, the leaflets
24 may have a thickness that is substantially
thinner than a wall thickness of the rest of the distal portion
18, preferably
tapering towards their distal tips
24a as shown in FIGS. 1A and 1B,
thereby enhancing the flexibility of the leaflets
24. The tapering thickness
may also ensure that the leaflets
24 are biased towards the closed position,
yet may deflect easily to accommodate a guidewire (not shown), bumper extension
element, and the like, as described further below.
Returning to FIG. 1B, in a preferred embodiment, the apparatus
10
also includes an elongate bumper member
30 that is slidably disposed within
the sheath
12. The bumper member
30 preferably includes a proximal
end (not shown), a distal end
32, and a lumen
34 that extends therebetween.
The bumper member
30 preferably has a substantially uniform outer diameter
slightly smaller than the interior lumen
16 of the sheath
12, preferably
by about 0.003-0.005 inch (0.075-0.125 mm) to create a close sliding, but not interfering,
fit between the bumper member
30 and the sheath
12. The lumen
34
has a diameter sufficiently large to accommodate a guidewire (not shown) therethrough,
preferably between about 0.015-0.020 inch (0.375-0.500 mm), and more preferably
about 0.016 inch (0.400 mm).
In a preferred form, the bumper member
30 is formed from a helical wire
compression coil
36, e.g., having adjacent turns that substantially abut
one another. The coil
36 may be formed from flat or round wire, e.g., of
stainless steel and the like, that is continuously helically wound along the length
of the bumper member
30, preferably a solid height coil. A relatively thin
layer of teflon
38 and the like may be provided around the outside of the
coil
36 to enhance a sliding relationship between the bumper member
30
and the sheath
12. Because of the coil
36, the bumper member
30
may be substantially resistant to buckling or kinking, while facilitating bending
of the bumper member
30 transverse to the longitudinal axis
28.
A substantially rigid tubular segment (not shown) may be attached to or otherwise
extend from the proximal end of the coil
36. Preferably, the tubular segment
is a section of hypotube having an inner lumen (not shown) similar to the lumen
34 of the coil
36, and more preferably a two-stage length of hypotube
that has a greater outer diameter on its proximal-most end. The tubular segment
may facilitate distal advancement of the bumper member
30 into the sheath
12 with minimal risk of buckling and/or may provide enhanced tactile perception
of relative movement of the bumper member
30 and the sheath
12. A
valve or other seal (not shown), e.g., for accommodating a guidewire therethrough
while maintaining a fluid-tight seal, may also be provided on the proximal end
of the tubular segment.
The bumper member
30 also includes a tubular bumper element
40
on a distal end
37 of the coil
36 that includes a substantially blunt
distal edge
42. The bumper element
40 is preferably formed from pebax
or other plastic material. A plastic bumper element
40 ensures no metal-to-metal
contact, e.g., between the coil
36 of the bumper member
30 and the
stent
50 that may lead to corrosion of the stent material. In addition,
pebax and other substantially flexible materials may deform slightly, e.g., when
the sheath
12 is retracted, to enhance contact between the blunt distal
edge
42 of the bumper element
40 and the stent
50. The bumper
element
40 is preferably attached to the distal end
37 of the coil
36, e.g., by heating the bumper element
40 to soften it and directing
it over the distal end
37, such that the bumper element is fused into the
coils adjacent the distal end
37.
The bumper member
30 may also include a radiopaque or other marker
48
thereon for identifying a location of the bumper member
30 using external
imaging, such as fluoroscopy. Preferably, a platinum iridium ring
48 is
provided on the bumper element
40 immediately adjacent the blunt distal
edge
42, thereby identifying a position of the proximal end
52 of
the stent
50. Alternatively, a marker (not shown) may be provided elsewhere
on the apparatus
10 in addition to or instead of the marker
48, such
as on the sheath
12 or the stent
50 itself. Thus, the marker
48
may facilitate positioning of the apparatus
10, and more particularly the
stent
50 or other element therein, axially within a body lumen (not shown)
before deploying the element from within the sheath
12, as described further below.
The bumper member
30 may also include a tubular extension element
44
that is thermally bonded or otherwise attached to and extends distally from the
bumper element
40. The extension element
44 has an outer diameter
that is substantially smaller than the bumper element
40 For example, the
extension element
44 may be partially inserted into the bumper element
40
as it is thermally bonded thereto so as not to interfere with the blunt edge
42
of the bumper element
40. Preferably, the extension element
44 has
an outer diameter of about 0.66 mm (0.026 inch) to facilitate its insertion through
the stent
50, an inner diameter of about 0.41 mm (0.016 inch) to accommodate
a guidewire therethrough, and a length of about 25 mm (1.0 inch). The extension
element
44 may be appropriately sized larger or smaller to accommodate a
guidewire, for example, between about 0.009-0.038 in (0.225-0.95 mm). The extension
element
44 is preferably substantially flexible and has a substantially
smooth outer surface to provide a low-friction, sliding contact with an element
disposed within the sheath
12.
In a preferred embodiment, a stent
50 or other tubular prosthesis or graft
may be disposed within the lumen
16 of the sheath
12 proximate the
distal portion
18. The stent
50 preferably is expandable between
a contracted condition that facilitates its loading into the lumen
16 of
the sheath
12, and an enlarged condition for engaging a wall of a blood
vessel or other body lumen (not shown). In a preferred embodiment, the stent
50
is a coiled-sheet stent, such as that disclosed in U.S. Pat. No. 5,443,500 issued
to Sigwart, and/or in co-pending application Ser. No. 09/347,845, filed Jul. 2,
1999, and Ser. No. 09/406,984, filed Sep. 28, 1999, the disclosures of which are
incorporated herein by reference. The stent
50 may be self-expanding, i.e.,
may be biased to assume the enlarged condition, but may be compressed and constrained
in the contracted condition, for example, by the lumen
16 of the sheath
12. Alternatively, the stent
50 may be plastically deformable, i.e.,
may be substantially relaxed in the contracted condition, but may be forcibly expanded
to the enlarged condition, for example, using a balloon catheter, as is known in
the art.
Preferably, the apparatus
10 is provided pre-assembled with the
stent
50 disposed within the lumen
16 of the sheath
12 adjacent
the distal portion
18 of the sheath in its contracted condition. The bumper
member
30 is also disposed within the lumen
16 such that the blunt
edge
42 of the bumper element
40 is adjacent a proximal end
52
of the stent
50. The extension element
44 preferably extends distally
through the stent
50 and through the leaflets
24, as best seen in
FIGS. 1B and 2B. The extension element
44 may facilitate insertion of a
guidewire (not shown) through the apparatus
10, i.e., through the lumen
16 of the sheath
12 into the lumen
34 of the bumper member
30 to a to proximal end of the apparatus
10. Preferably, the opening
25 at the apices of the leaflets
24 accommodates the extension element
44 therethrough without causing the leaflets
24 to partially buckle
or bulge.
Alternatively, the extension element
44 may be eliminated,
and a guidewire inserted directly between the leaflets
24 into the lumens
16,
34. The apparatus
10 may be used to implant the stent
50 within a body lumen, preferably within a carotid artery, a coronary artery,
a cerebral artery, a renal artery, or other blood vessel, as described further
below. In a further alternative, the apparatus
10 may incorporate "rapid
exchange" configurations where a guidewire may exit from the lumens
16,
34 of the sheath
12 and/or bumper member
30 through side ports
(not shown) at a location along their lengths, i.e., at an intermediate location,
rather than at their proximal ends, as is known to those skilled in the art. To
accommodate a guidewire between the sheath
12 and the bumper member
30
during retraction, a longitudinal slot (not shown) may be provided in either the
inner surface of the sheath or the outer surface of the bumper adjacent the side ports.
Turning to FIGS. 3A-3E, a method is shown for forming a rounded bullet-shaped
distal portion
18 on a tubular sheath
12 and the like. A tubular
sheath
12 is provided that is formed from substantially flexible plastic
material, such as those described above, preferably pebax, and that has a lumen
16 therein extending from the distal end
14 towards the proximal
end (not shown). The sheath
12 initially has a distal end
14 that
terminates in a substantially blunt distal edge
19 (FIG. 3A).
In a preferred embodiment, the sheath
12 has a plurality of segments having
varying degrees of flexibility, for example, including a distal portion
18,
an intermediate portion (not shown), and a proximal portion (also not shown). Preferably,
the distal portion
18 is a predetermined length of pebax tubing that is
thermal bonded, e.g., butt bonded to the intermediate portion, which is a predetermined
length of pebax tubing reinforced by a stainless steel braid, such as the lengths
described above. The intermediate portion, in turn, is thermally bonded to a predetermined
length of nylon tubing. Alternatively, an adhesive, connectors, and the like may
be used to attach two or more of the portions to one another.
Preferably, the sheath
12 is pre-assembled, i.e., with the distal,
intermediate, and proximal portions bonded to one another before the distal portion
18 is formed into its bullet shape, as described below. Alternatively, the
distal portion
18 may be formed into its bullet shape and/or other steps
of the method performed before the distal portion
18 is attached to the
intermediate portion.
A stent
50 or other prosthesis is disposed within the lumen
16,
preferably
a predetermined distance from the distal end
14 of the sheath
12.
Preferably, the stent
50 is constrained in its contracted condition, and
inserted into the distal end
14 of the sheath
12 before the distal
portion
18 is formed into its bullet shape. Alternatively, the stent
50
may be provided in its contracted condition, and introduced into the lumen
16
from the proximal end of the sheath
12, e.g., either before or after the
distal portion
18 is formed into its bullet shape.
In a preferred embodiment, the stent
50 is a self-expanding tubular member
formed from Nitinol having a transition temperature between ambient and body temperatures.
The stent
50 may be formed into its enlarged condition in its austentic
phase (e.g. by hand rolling for a coiled-sheet stent) and heat treated to set the
enlarged condition in its shape memory. The stent
50 may then be chilled
to its martensitic phase, e.g., at a temperature below ambient temperature, and
preferably between about 0-10 degrees Celsius, for example, by blowing liquid Nitrogen
onto the stent
50. The stent
50 may then be pulled through one or
more draw-down fixtures, i.e., tapered tubular dies (not shown), which may be chilled,
to plastically compress the stent
50 into a contracted condition. In the
contracted condition, the stent
50 preferably has a diameter substantially
smaller than the lumen
16 of the sheath
12. The stent
50 may
then be pulled from the draw-down fixture into the lumen
16 of the sheath
12. In a preferred method, a teflon tubular guide or sheath (not shown)
may be used to facilitate sliding the stent
50 through one or more of the
draw-down fixtures. The stent
50 may be pulled into the teflon guide as
it enters a draw-down fixture, the teflon guide being split or otherwise removed
from the stent
50 before it is pulled into the sheath
12.
The bumper member
30 (not shown in FIGS. 3A-3C) may be inserted into the
lumen
16 of the sheath
12 until the extension element
44 approaches,
but does not extend from, the distal end
14 of the sheath
12. For
example, the blunt edge
42 of the bumper element
40 may abut the
proximal end
52 of the stent
50, with the extension element
44
extending therethrough. Alternatively, the bumper member
30 may not be extended
distally to abut the stent
50 until after the distal portion
18 is
formed into its bullet shape. In a further alternative, the bumper member
30
may not be introduced into the sheath
12 until after the distal portion
18 is formed into its bullet shape.
Returning to FIGS. 3A-3C, a die
60, e.g., a spherically shaped "hot
die," is provided having a bore or other recess
62 therein. The bore
62
has an entry
64 with a cross-section substantially similar to the cross
