U.S. patent application number 12/508608 was filed with the patent office on 2009-11-12 for balloon catheter stent delivery system with ridges.
Invention is credited to Eric Gerard Johnson.
Application Number | 20090281612 12/508608 |
Document ID | / |
Family ID | 32393665 |
Filed Date | 2009-11-12 |
United States Patent
Application |
20090281612 |
Kind Code |
A1 |
Johnson; Eric Gerard |
November 12, 2009 |
BALLOON CATHETER STENT DELIVERY SYSTEM WITH RIDGES
Abstract
A balloon catheter and stent delivery system for medical
treatment of a patient includes a balloon having a pattern of
ridges in an initial deflated state. The ridges may cooperate with
structural elements of a stent crimped onto the balloon, to
increase and enhance longitudinal retention of the stent while the
catheter system is advanced or withdrawn. Upon inflation, the
balloon recovers to an inflated shape having a cylindrical working
portion. The balloon catheter thus provides for uniform expansion
of the stent when the balloon is inflated. The present invention
also tends to protect the leading or distal end of the stent during
advancement, and tends to protect the leading or distal end of the
stent during advancement, and tends to protect the proximal end of
the stent during any withdrawal of the catheter system.
Inventors: |
Johnson; Eric Gerard; (New
Albany, IN) |
Correspondence
Address: |
PHILIP S. JOHNSON;JOHNSON & JOHNSON
ONE JOHNSON & JOHNSON PLAZA
NEW BRUNSWICK
NJ
08933-7003
US
|
Family ID: |
32393665 |
Appl. No.: |
12/508608 |
Filed: |
July 24, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10466029 |
Dec 24, 2003 |
7572270 |
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PCT/US02/04636 |
Feb 15, 2002 |
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12508608 |
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60269430 |
Feb 16, 2001 |
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Current U.S.
Class: |
623/1.12 ;
604/96.01; 606/194; 623/1.46 |
Current CPC
Class: |
A61F 2/958 20130101;
A61F 2002/9583 20130101 |
Class at
Publication: |
623/1.12 ;
604/96.01; 623/1.46; 606/194 |
International
Class: |
A61F 2/06 20060101
A61F002/06; A61M 29/00 20060101 A61M029/00 |
Claims
1-17. (canceled)
18. A balloon catheter, comprising: a flexible shaft having a
proximal and a distal end; a hub affixed to the proximal end of the
shaft; a balloon affixed to the shaft near the distal end, the
balloon being inflatable from a deflated state to an inflated
state, the shaft defining an inflation lumen for conducting
inflation fluid from an inflation port defined by the hub to an
interior of the balloon; wherein the balloon in an initial deflated
state is pleated and wrapped around the shaft; the balloon in the
initial deflated state having a plurality of ridges; the ridges
each extending radially outward a first radial distance which is
greater than a default radial dimension defined by portions of the
balloon between each of the ridges; a pair of shoulders defined by
the balloon flanking the central series of ridges and disposed near
a proximal and distal end of the balloon respectively; each of the
shoulders generally extending circumferentially around the balloon,
and each shoulder extending radially outward a second radial
distance which is greater than the first radial distance; the
ridges and shoulders being adapted to receive a stent and resist
longitudinal movement of a stent crimped onto the balloon.
19. The balloon catheter of claim 18 wherein the ridges extend
generally circumferentially around the balloon.
20-24. (canceled)
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority of U.S. Provisional Patent
Application No. 60/269,430 filed Feb. 16, 2001.
BACKGROUND AND SUMMARY OF THE INVENTION
[0002] 1. Technical Background:
[0003] The present invention relates generally to medical devices,
and more particularly to a balloon catheter and stent delivery
system.
[0004] 2. Discussion
[0005] The present invention involves a balloon catheter for
inserting a stent, vascular scaffold, or other medical device to a
desire site in a patient for medical treatment. The balloon is
specially shaped with structural features for cooperating with
corresponding stent designs to enhance stent retention.
[0006] For purposes of brevity, the following background and
description will focus generally on the example of a medical device
delivery system, in which the medical device is a stent, and the
delivery system is based on a balloon catheter. Of course, other
medical devices and other delivery systems that are within the
scope of one of the Claims below are included in the present
invention.
[0007] It is desirable to provide a novel combination stent
delivery system, along with a unique manufacturing process, having
an optimum arrangement of several features. These desirable
features include a tendency to retain the stent in position on a
deflated balloon, small initial size or profile, bending
flexibility, column stiffness or pushability, pull strength,
inflation strength (sometimes referred to as "rated burst
pressure"), etc.
[0008] To provide an optimum arrangement of these features, the
present invention recognizes and takes advantage of structural
aspects of certain stents, such that the delivery system optimizes
stent retention without comprising any of the other performance
qualities.
[0009] Among the stent structural features that may be utilized by
the present invention are an expandable cylindrical mesh or
lattice, stents are preferably designed to be flexible during
delivery and bend along a vascular path. One design that allows
such flexibility is to include a series of main elements for hoop
strength, preferably coupled by a series of flexible links to
enhance flexibility. The stent should preferably also have an
optimum selection of features, including flexibility, small
profile, hoop strength when expanded, and resilience, etc.
[0010] Accordingly, stent delivery systems of the present invention
provide balloons for delivery and expanding the stent, in which the
balloon has a deflated shape with a pattern of ridges or bumps.
These ridges or bumps tend to increase stent retention during
delivery, and preferably cooperate with the pattern of main stent
elements and flexible links, to better hold the stent in place on
the catheter delivery system.
[0011] Background:
[0012] Balloon catheters are used in a variety of therapeutic
applications, including intravascular catheters for procedures such
as angioplasty treating coronary, neurological and peripheral blood
vessels partially or totally blocked or narrowed by a stenosis. By
way of example, the present invention will be described in relation
to coronary and peripheral angioplasty treatments. However, it
should be understood that the present invention relates to balloon
catheters and stent delivery systems generally, and is not limited
to the specific embodiments described herein.
[0013] Most balloon catheters have a relatively long and flexible
tubular shaft defining one or more passages or lumens, and an
inflatable balloon attached near one end of the shaft. This end of
the catheter where the balloon is located is customarily referred
to as the "distal" end, while the other end is called the
"proximal" end. The balloon is connected to one of the lumens
extending through the shaft to selectively inflate and deflate the
balloon. The other end of this inflation lumen leads to a hub
coupling at the other end for connecting the shaft lumens to
various equipment. Examples of this type of balloon catheter are
shown in U.S. Pat. No. 5,304,197, entitled "Balloons For Medical
Devices And Fabrication Thereof," issued to Pinchuk et al. on Apr.
19, 1994, and also in U.S. Pat. No. 5,370,615, entitled "Balloon
Catheter For Angioplasty," issued to Johnson on Dec. 6, 1994.
[0014] A common treatment method for using such a balloon catheter
is to advance the catheter into the body of a patient, by directing
the catheter distal end percutaneously through an incision and
along a body passage until the balloon is located within the
desired site. The term "desired site" refers to the location in the
patient's body currently selected for treatment by a health care
professional. A larger guiding catheter may often be used to access
the local area near the desired site, providing a smooth, supported
lumen for conducting other devices including balloon catheters to
the desired site. After the balloon is within the desired site, it
can be selectively inflated to press outward on the body passage at
relatively high pressure to a relatively constant diameter, in the
case of an inelastic or non-complaint balloon material.
[0015] This outward pressing of a constriction or narrowing at the
desired site in a body passage is intended to re-open or dilate
that body passageway or lumen, increasing its inner diameter or
cross-sectional area. When performed in a blood vessel, this
procedure is called "angioplasty." The narrowing of the body
passageway lumen is called a lesion or stenosis, and may be formed
of hard plaque or viscous thrombus. The objective of this
angioplasty procedure is to treat the lesion by increasing the
cross-sectional area of the blood vessel, to encourage greater
blood flow through the newly expanded vessel.
[0016] Unfortunately, the lumen at the angioplasty site may
re-close or become narrow again. This possible phenomenon is called
restenosis, and may occur in a certain percentage of percutaneous
transluminal angioplasty patients. Restenosis may require an
additional procedure, such as another angioplasty, drug therapy
treatment, or even surgery including bypass graft.
[0017] Stents:
[0018] In an effort to prevent restenosis, a short flexible
cylinder or scaffold made of metal or polymers, referred to as a
stent, may be permanently implanted into the vessel to hold the
lumen open, to reinforce the vessel wall and improve blood flow. In
1998, coronary stents were placed in an estimated half million
patients in the United States. The presence of a stent tends to
successfully keep the blood vessel open longer, but their use may
be limited by various factors, including size and location of the
blood vessel, a complicated or tortuous vessel pathway, etc. Also,
even a vessel with a stent may eventually develop restenosis.
[0019] One type of stent is expanded to the proper size at the
desired site within the lesion by inflating a balloon catheter,
referred to as "balloon-expandable" stents. Balloon-expandable
stents are crimped or compressed onto a deflated balloon, to a
diameter during delivery that is smaller than the eventual deployed
diameter at the desired site.
[0020] However, friction forces during delivery may tend to cause a
crimped stent to slip in a proximal direction while the catheter
system is advanced, or possibly to slip in a distal direction if
the physician decides to withdraw the stent without deploying it.
It is of course desirable to retain the stent in the proper
position during movement, both advancement along a vascular path to
the desired site, as well as, subsequent removal if necessary.
[0021] In addition, it is desirable to provide a stent delivery
system with greater stent retention, that is more capable of
holding the stent in position, or also of advancing a crimpled
stent across a previously deployed stent, or possible withdrawing
it into a guiding catheter.
[0022] Drug Delivery:
[0023] The present invention is preferably used with a stent or
other medical device that may be provided with one or more
coatings, to achieve even greater effectiveness. Such coating or
coatings may be selected among various coatings, including
therapeutic coatings such as anticoagulants, antiproliferatives, or
antirestenosis compounds.
[0024] For example, a preferred coating for a stent is an
anticoagulant coating such as heparin. Another preferred coating is
an antirestenosis compounds, such as for example rapamycin (which
is also known as sirolimus). Such a compound can be very effective
at resisting a vessel from re-closing. Any particular coating or
type of coating may of course be used independently or in
conjunction with any one or more coatings, as desired.
[0025] Some pioneering research in drug-coated stents has been
conducted, and is described in the following publications, all of
which are assigned to Cordis Corporation and are incorporated
herein by reference: (i) European Patent Application number EP
99/302918 A2, entitled "Stent With Local Rapamycin Delivery" by
Wright et al., filed on Apr. 15, 1999; (ii) PCT Patent Application
number US0115562, entitled "Delivery Devices For Treatment Of
Vascular Disease" by Falotico et al., filed on May 14, 2001; and
(iii) PCT Patent Application number US0115564, entitled "Drug/Drug
Delivery Systems For The Prevention And Treatment Of Vascular
Disease" by Falotico et al., filed on Oct. 14, 2001.
[0026] Accordingly, it is an object of the present invention to
provide balloon catheter systems for enhanced position retention of
a stent or other medical device during longitudinal movement of the
catheter.
[0027] It is a further object of the present invention to provide
methods for making balloon catheter systems having enhanced
position retention of a stent or other medical device.
[0028] It is a further object of the present invention to provide
methods for making balloon catheters for enhanced stent position
retention.
[0029] These and various other objects, advantages and features of
the invention will become apparent from the following description
and claims, when considered in conjunction with the appended
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] FIG. 1 is an external perspective view of a balloon catheter
having a stent mounted around the balloon, arranged according to
the principles of the present invention;
[0031] FIG. 2 is a longitudinal cross-section view of a balloon
catheter according to the principles of the present invention;
[0032] FIG. 3 is a partial cross-section view of a balloon and a
corresponding partial pattern view of a section of a stent;
[0033] FIG. 4 is a series of partial longitudinal cross-section
views of balloons according to alternate embodiments of the present
invention;
[0034] FIG. 5 is a partial longitudinal cross-section view of a
stent and a balloon catheter, showing a fully inflated balloon;
[0035] FIGS. 6-8 are partial elevation views of a balloon catheter
distal end and a stent; and
[0036] FIG. 9 is a perspective view of an example of balloon
forming equipment according to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0037] The following description of the preferred embodiments of
the present invention is merely illustrative in nature, and as such
it does not limit in any way the present invention, its
application, or uses. Numerous modifications may be made by those
skilled in the art without departing from the true spirit and scope
of the invention.
[0038] The present invention relates to a medical device delivery
system having a balloon that is specially shaped when deflated with
a series of ridges or bumps, for cooperating with corresponding
designs of the medical device to enhance position retention of the
medical device during movement of the system. The present invention
may preferably be used with a medical device having one or more
coatings, such as a therapeutic drug coating.
[0039] Balloon Catheters:
[0040] Referring to the drawings, a balloon catheter system is
depicted, with one of the preferred embodiments of the present
invention being shown generally at 10. The balloon catheter of FIG.
1 has an inflatable balloon 12, a relatively long and flexible
tubular shaft 14, and a hub 16. The balloon 12 is affixed to the
shaft 14 near a distal end of the shaft 14, and the hub 16 is
affixed to the proximal end of the shaft 14.
[0041] The shaft 14 defines one or more passages or lumens
extending through the shaft, at least one of which is an inflation
lumen 18 connected to the balloon 12 for the purpose of selectively
inflating and deflating the balloon 12. The inflation lumen 18 thus
provides fluid communication between the interior of the balloon 12
at the distal end of the inflation lumen 18, and a hub inflation
port 20 having a coupling or luer-lock fitting at the proximal end
for connecting the inflation lumen 18 to a source of pressurized
inflation fluid (not shown) in the conventional manner.
[0042] In the illustrated embodiment, the shaft 14 is constructed
of an inner and outer tubular body 22 and 24. The inner body 22
defines a guidewire lumen 26, while the inflation lumen 18 is
defined by the annular space between the inner and outer tubular
bodies 22 and 24. The guidewire lumen 26 is adapted to receive an
elongated flexible guidewire 28 in a sliding fashion, such that the
guidewire 28 and catheter 10 may be advanced or withdrawn
independently, or the catheter 10 may be guided along a path
selected with the guidewire 28. The shaft 14 may of course have
various configurations instead of this coaxial design, including a
single extruded tube defining any suitable number of parallel
side-by-side lumens, or a proximal shaft portion formed of a metal
hypotube connected to a polymer distal shaft portion or other
designs. Moreover, the catheter shaft may have a rapid exchange
configuration, in which the guidewire exits the shaft at a proximal
guidewire port located between the balloon and the hub.
[0043] The proximal hub 16 is affixed to the proximal end of the
shaft 14, and preferably provides an inflation port 20 and a
guidewire port 30, again with a luer-lock fitting or hemostatic
valve (not shown). Such a valve allows the guidewire 28 to traverse
and slide within the guidewire lumen 26, yet while resisting the
loss of blood or other fluids through the guidewire lumen 26 and
guidewire port 30.
[0044] As shown in the drawings, the inner and outer tubular bodies
22 and 24 are securely received within the hub 16, and surrounded
by a tubular strain relief 32. The hub 16 provides fluid
communication between the guidewire lumen 26 and a guidewire port
30 as well as between the annular inflation lumen 18 and the
inflation port 20 and coupling.
[0045] As shown in the drawings, in particular FIG. 5, the balloon
12 in its fully inflated profile shape has a cylindrical working
portion 36 with an inflated diameter located between a pair of
conical end portions 38, and a pair of proximal and distal legs 40
and 42 affixed to the shaft 14. In its deflated shape, the balloon
12 preferably has several pleats that are wrapped round the shaft.
The balloon pleats are illustrated in
[0046] FIGS. 1 and 6-8 in diagrammatic fashion, but are omitted
from the other drawings for the sake of clarity.
[0047] Radiopaque markers may be used to indicate the position(s)
of certain components or features on an x-ray video fluoroscope.
For example, marker bands 68 may be attached to the inner body 22
as shown in FIG. 5, to indicate the positions of the proximal and
distal ends of a stent 34.
[0048] Various materials for balloon catheter components are well
known. For example, the balloon material is preferably
substantially inelastic, and as such it stretches a relatively
small amount under pressures of up to 15 atmospheres or more.
Different balloon materials may be used, including nylon, PEEK,
polymer materials sold under the trade name Pebax or Plexar,
polyethylene, HDPE, polyurethane, or a block copolymer thereof.
Likewise, various materials may be used for the shaft components
and strain relief, including for example all of the materials
listed above, as well as others including metal such as a stainless
steel hypotube for example. The hub may be made of a hard plastic,
such as for example polycarbonate. Markers 68 may be made of any
suitably radiopaque material, metal, alloy, or combination of
materials, including for example tungsten or platinum.
[0049] Also, various material structures may be used for any of the
components, including for example multilayer structures such as two
layers with different properties, or reinforced or braided
structures.
[0050] Stents and Other Medical Devices:
[0051] A stent of any suitable type or configuration may be
provided with a catheter 10 of the present invention. Preferably,
stents for the present invention should have an optimum selection
of various features, including among others: a generally
cylindrical shape, small initial diameter, large deployed diameter,
flexibility, high hoop strength when deployed, closed cell
construction, and certain other desirable performance
characteristics common to balloon-expandable stents. Any stent
design having the desired characteristics may be used with the
present invention.
[0052] Various kinds and types of stents are available in the
market, and some different currently available stents are
acceptable for use in the present invention, as well as new stents
which may be developed in the future. The stent 34 depicted in the
drawings is a cylindrical metal mesh stent having an initial
crimpled outer diameter, which may be forcibly expanded by the
balloon to a deployed diameter. When deployed in a body passageway
of a patient, the stent may be designed to preferably press
radially outward to hold the passageway open.
[0053] An example of a stent with a preferred combination of
features is known as the Bx Velocity, available from Cordis
Corporation in Miami, Fla. The Bx Velocity stent has an
advantageous arrangement illustrated in FIG. 3, including an
alternating series of structural elements for strength and flexible
links for flexibility. Of course, the present invention may be used
with any stent having a suitable configuration.
[0054] Among the stent structural features that may be included in
such a suitable configuration are an expandable cylindrical mesh or
lattice, designed to be flexible and bend along a vascular path. An
example of a possible design having these features may include a
series of main structural elements 64 for hoop strength, coupled by
a series of flexible links 66 to enhance flexibility.
[0055] The present invention may be used with any other medical
device having the requisite features, and which is delivered by a
catheter delivery system with the claimed elements.
[0056] Preferably, the stent or other medical device may be
provided with one or more coatings. Such coating or coatings may be
selected among various coatings, including therapeutic coatings
such as anticoagulants, antiproliferatives, or antirestenosis
compounds.
[0057] For example, a preferred coating for a stent is an
anticoagulant coating such as heparin. Another preferred coating is
an anti-restenosis compound, such as for example rapamycin (which
is also known as sirolimus). Such a compound can be very effective
at resisting a vessel from re-closing. Any particular coating or
type of coating may of course be used independently or in
conjunction with any one or more coatings, as desired.
[0058] Because the stent is most often or most likely to be made of
metal, for example stainless steel or nitinol, it is preferable
that a coating be applied with or used in conjunction with one or
more polymers. For example, an initial polymer coating may
preferably be applied to the stent. The therapeutic compound may be
applied directly or may be embedded in another polymer coating, as
desired.
[0059] The balloon catheter may be used for inserting a stent,
vascular scaffold or other medical device to a desired site in a
patient for medical treatment, in which the balloon is specially
shaped with structural features for cooperating with corresponding
designs of the medical device to enhance position retention.
[0060] An optimum combination of features for the device and
delivery system include a small initial size or profile, bending
flexibility, column stiffness or pushability, pull strength,
inflation strength (sometimes referred to as "burst pressure"), and
a tendency to retain the stent in position on a deflated
balloon.
[0061] To provide an optimum arrangement of these features, the
present invention recognizes and takes advantage of structural
aspects of certain stents, such that the delivery system optimizes
stent retention while maintaining the performance qualities.
[0062] Ridges or Bumps:
[0063] Accordingly, medical device delivery systems of the present
invention provide balloons with a deflated shape having a pattern
of radially extending ridges 50. These ridges 50 preferably
cooperate with the pattern of main structural elements and flexible
links, to hold the stent in place on the catheter delivery
system.
[0064] A novel balloon catheter system of the present invention
provides several advantages. Among these advantages is that the
balloon in an initial deflated state has a series of ridges or
bumps for cooperating with the structure of the selected stent, to
enhance stent position retention. This improved stent retention
results from crimping a stent around a previously formed balloon
having the ridges of the present invention. After crimping, the
circumferential ridges formed on the balloon increase stent
retention of the delivery system. In the currently preferred
embodiment as shown in FIG. 3, the ridges 50 and valleys 48 of the
deflated balloon 12 are preferably aligned with a corresponding
series of structural stent elements.
[0065] Such alignment of the balloon ridges and the stent
structural elements preferably involves sizing and positioning each
ridge within and surrounded by a corresponding generally
cylindrical stent structural element. In other words, as
illustrated in FIG. 3, each structural element portion of the stent
pattern is preferably arranged to match and be crimped around a
corresponding ridge formed on the balloon. The remaining portions
of the stent pattern between structural elements, preferably
flexible linkages of some kind, should match and be crimped around
the remaining portions of the balloon between ridges.
[0066] Of course, the inverse arrangement is also within the scope
of the present invention in which the structural elements of the
stent are aligned between, rather than aligned with, the balloon
ridges.
[0067] In general, the present invention relates preferably to a
stent having a repeating serial pattern, aligned and arranged with
a corresponding repeating pattern of shaped features or ridges
formed on a deflated, pleated and wrapped balloon on a
catheter.
[0068] The balloon pattern of shaped features or ridges may also
have various shapes, examples of which are shown in FIGS. 4a-c. The
size and shape of the balloon ridges or bumps may be varied to suit
preferences, or to optimally accommodate various designs of the
stent or of the medical device. FIG. 4a for example shows a balloon
having valleys 56 and elliptical ridges 58. FIG. 4b shows a balloon
having adjacent rounded lobes 60. FIG. 4c shows a balloon having an
undulating or sinusoidal series of shapes 62.
[0069] In addition, the balloon preferably defines a pair of
shoulders 44 and 46 in the initial deflated shape, proximal and
distal of the stent, to further enhance the tendency of the stent
to maintain position on the balloon, as well as providing a smooth
and gentle surface during advancement and possible retraction of
the stent into position. This coordinated design of the balloon and
stent optimizes many of the desired performance features of the
stent delivery system in general, and increases stent retention in
particular.
[0070] These preferably curved annular shoulders immediately
adjacent the proximal and distal ends of the stent should have a
diameter equal to or greater than the crimped stent, thus
protecting the stent and minimizing any possibility of the stent
moving due to friction. The shoulders and transition portions may
also tend to act as dilators, to encourage easy advancement through
challenging anatomy or previously deployed stent, or withdrawal
into the guiding catheter. The proximal and distal shoulders may be
of any desirable shape, with preferably an outer dimension greater
than the crimped stent.
[0071] Accordingly, the balloon also has a composite profile shape
which varies at different pressures. The balloon initially is in a
deflated state and has a deflated profile shape, as specifically
illustrated in FIG. 2, having a central bed portion with a deflated
bed diameter being flanked by a pair of proximal and distal
shoulders 44 and 46 defining deflated shoulder diameters that are
preferably larger than the deflated bed diameter.
[0072] The balloon shoulders taper smoothly down to proximal and
distal cylindrical balloon leg 40 and 42. The proximal balloon leg
40 is affixed to the outer tube 24, while the distal balloon leg 42
is affixed to the inner tube 22. This deflated balloon profile
shape thus provides a bed or nest portion for receiving the stent
34 and tending to hold the stent 34 in place, while minimizing
friction or adverse contact between the ends of the stent 34 and a
blood vessel wall. The present invention thus tends to protect the
leading or distal ends of the stent 34 during advancement into the
patient's body, and the proximal end of the stent 34 during any
withdrawal of the catheter system.
[0073] FIG. 5 depicts the balloon 12 in its fully inflated profile
shape. The shoulders and ridge shapes disappear, and the balloon
profile shape changes or morphs into a different profile shape when
inflated at full inflation pressure. This fully inflated shape
provides the preferable cylindrical working portion 36, wherein the
portion of the balloon supporting and expanding the stent 34 has an
inflated diameter larger than any other portion of the balloon 12.
This feature tends to prevent any part of the balloon from
expanding excessively, which might cause local trauma to the blood
vessel wall.
[0074] In the deflated shape, the balloon is therefore temporarily
reformed into a different shape than what might conventionally
result from simply deflating and pleating a previously known
balloon. This temporarily reformed shape enhances stent position
retention, and yet exhibits the preferable fully inflated
shape.
[0075] Many modification can of course be made to the present
invention, and may alternate embodiments of the present invention
are possible. Some examples include forming discrete bumps or any
other shapes of protrusion, rather than circumferential ridges.
Likewise, the ridges or bumps may extend radially outward to
differing distances, for example an arrangement of major and minor
features. Bumps or features on the same balloon may have different
shapes as well as sizes. It is possible that balloon bumps or
ridges may extend through or among interstices or gaps in the
stent, or have an outer dimension greater than and extending beyond
the outer diameter of the stent.
[0076] Another advantage of the present invention is the absence of
any type of physical collar or other retaining device within the
balloon, or on the outer balloon surface, or mounted on the balloon
catheter shaft, which might undesirably increase the primary and/or
secondary profiles of the stent delivery system.
[0077] The dimensions that may be preferred for the present
invention will of course vary, as the device is sized to a
patient's vascular anatomy. The following dimensions are for
example only, and will vary greatly depending on the patient's
anatomy; desired area such as coronary vascular, endovascular, or
esophageal areas. Accordingly, all of the following dimensions are
in inches, and represent only an approximate average of a preferred
range of 100%.
[0078] The outer diameters of the inner body may be 0.025, of a
proximal or distal shoulder may be 0.040-0.060, of the base stent
bed may be 0.030-0.050, and of the bumps or ridges may be
0.035-0.065. The longitudinal length of the proximal or distal
shoulder may be 0.250, of the bumps or ridges may be 0.030-0.045,
and of the gap or distance between bumps or ridges may be
0.040-0.060.
[0079] Of course, the ridges may be made by any suitable method,
and may have any suitable shape and arrangement, in accordance with
the scope of the present invention. The present invention may be
made for example using any of the following methods, as well as
various modifications that will be apparent to those skilled in the
art.
[0080] First, a balloon catheter is assembled using generally
conventional methods of extrusion, injection molding, and adhesive
or heat-sealing for example. Then the balloon is preferably
pleated, in which the balloon is folded into any suitable or
preferable number of longitudinal pleats. The pleated balloon is
preferably heated slightly for a short time, to cause the balloon
material to accept a "memory" or a preference for a pleated
configuration when deflated. Of course, the pleating step may be
conducted in a conventional manner, but the "heat-pleating" step is
preferred. For example, if nylon balloon material is used, the
heat-pleating may be performed with a temperature of up to
approximately 70.degree. C. for up to about half a minute.
[0081] The pleated "wings" are then wrapped around a portion of the
catheter shaft all in the same direction, either manually or by
using a pleating machine.
[0082] The balloon is then temporarily held in its pleated
condition by slipping a forming tube in the proximal direction onto
the pleated balloon, while the assembly is transported to the next
processing station. The balloon is heated, preferably at
60-80.degree. C. for under 30 seconds.
[0083] The forming tube may then be removed. The folded and pleated
balloon is then placed in a mold 70 to form the desired balloon
bumps or ridges. A mold component is shown in FIG. 9, with one
possible configuration according to the present invention. The mold
70 is used with an identical and opposing mold, both of which have
a series of recesses 72 for creating the desired bumps or ridges. A
passage is formed through the mold 70, to allow the catheter to be
inserted within the mold 70. This passage has proximal and distal
extensions 76 and 74, and the passage extends fully through the
length of the mold 70. The proximal end of the proximal extension
76 is chamfered, beveled, or angled 78, to allow easy introduction
of the balloon into the mold 70. When the balloon is inside the
clamped mold 70, it is pressurized and heated for a time. The mold
70 may be made of any suitably heat-resistant and rigid material,
including a transparent material such as acrylic. The heat and
pressure may preferably be about 80-100.degree. C. and 175-225 psi
for about half a minute. The mold 70, which is preferably a pair of
"clam-shell" dies having specific shapes formed in their surfaces,
are preferably made of polycarbonate and acrylic inserts, inside a
heat-sealing machine. The mold 70 preferably as a desired series of
cylindrical and/or doughnut-shaped cut-outs or recesses 72 formed
on the interior surface of the mold 70, as illustrated in FIG.
9.
[0084] After the pressure is released, the pair of dies which form
the mold 70 are opened. The resulting balloon catheter assembly
thus exhibits the desirable ridges of the present invention.
[0085] A stent is placed over the shaped balloon, such that the
stent preferably has structural elements that align with the
balloon ridges. The alignment of the stent in position can be
facilitated by one or more marker bands on the balloon catheter
shaft. The resulting assembly may be placed in a crimping device,
which uniformly squeezes the stent onto the balloon. The stent is
then gently crimped or compressed around the balloon, with the
pleats, ridges and shoulders intact, to a crimped condition in
which the stent has a specific crimped outer diameter.
[0086] The balloon is then pressurized by applying a pressurized
fluid to the inflation port and through the inflation lumen. The
preferred pressure of the inflation within the tubular mold may
slightly exceed the rated burst pressure of the balloon, and the
mold will prevent expansion of the stent while allowing the
proximal and distal balloon shoulders to form. The pressurized
fluid may preferably be dry nitrogen, and the pressure may
preferably be maintained for a preselected period of time.
[0087] The mold may be formed as shown in FIG. 9. While the mold
with the accompanying balloon catheter and stent assembly is held
under pressure, they are then held in a hot box or heated die. The
heat tends to set the stent in place, thus forming the desired
proximal and distal shoulders 44 and 46. Of course, a hot air or
liquid system may also be used. The preferred temperature of the
heating system is preferably below the permanent deformation
temperature of the balloon material, and the time and pressure of
this process may be extended to ensure that such a temperature will
result in the desired composite shape and temporary reformation of
the balloon.
[0088] The pressure is released and the balloon and stent assembly
are then removed from the mold and heating system. In the
alternative, the pressure may be maintained as the balloon and
stent assembly is allowed to cool for a period of time.
[0089] Several features of this preferred method of making the
balloon catheter stent delivery system of the present invention
have an effect on the performance of the resulting product,
including the temperatures, pressures, time periods, crimped outer
diameter of the stent, the internal diameter of the mold, as well
as the thermal characteristics of the balloon, stent and mold.
These characteristics may be optimized and selected to result in a
desired combination of performance attributes for the end
product.
[0090] It should be understood that an unlimited number of
configurations for the present invention could be realized. The
foregoing discussion describes merely exemplary embodiments
illustrating the principles of the present invention, the scope of
which is recited in the following claims. Those skilled in the art
will readily recognize from the description, claims, and drawings
that numerous changes and modifications can be made without
departing from the spirit and scope of the invention.
* * * * *