U.S. patent application number 11/085830 was filed with the patent office on 2005-11-24 for focalized intraluminal balloons.
Invention is credited to Crocker, Michael, Shimada, Lynn M..
Application Number | 20050261722 11/085830 |
Document ID | / |
Family ID | 27539459 |
Filed Date | 2005-11-24 |
United States Patent
Application |
20050261722 |
Kind Code |
A1 |
Crocker, Michael ; et
al. |
November 24, 2005 |
Focalized intraluminal balloons
Abstract
Disclosed is a focal balloon having at least one reference zone
and a focal zone. In one embodiment, the reference zone and focal
zone are inflatable to a first generally cylindrical profile at a
first pressure. At a second, greater pressure, the focal section
expands to a second, greater diameter, while the reference zone
remains substantially at the first diameter. In an alternate
embodiment, the focal zone and the reference zone are inflatable to
their respective predetermined diameters at the inflation pressure,
in the absence of constricting lesions or anatomical structures.
Multiple lobed and drug delivery embodiments are also
disclosed.
Inventors: |
Crocker, Michael; (Anaheim,
CA) ; Shimada, Lynn M.; (Irvine, CA) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
2040 MAIN STREET
FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Family ID: |
27539459 |
Appl. No.: |
11/085830 |
Filed: |
March 21, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11085830 |
Mar 21, 2005 |
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10179468 |
Jun 24, 2002 |
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6872215 |
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10179468 |
Jun 24, 2002 |
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09564003 |
May 3, 2000 |
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6409741 |
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09564003 |
May 3, 2000 |
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09203228 |
Nov 30, 1998 |
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6120523 |
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09203228 |
Nov 30, 1998 |
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08742437 |
Oct 30, 1996 |
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5843116 |
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08742437 |
Oct 30, 1996 |
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08640533 |
May 2, 1996 |
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5645560 |
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10179468 |
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08670683 |
Jun 26, 1996 |
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6027486 |
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08670683 |
Jun 26, 1996 |
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08572783 |
Dec 15, 1995 |
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08572783 |
Dec 15, 1995 |
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08201935 |
Feb 24, 1994 |
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5470313 |
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Current U.S.
Class: |
606/192 |
Current CPC
Class: |
A61M 2025/1084 20130101;
A61M 2025/1075 20130101; A61F 2/86 20130101; A61M 25/104 20130101;
A61M 2025/1072 20130101; A61M 25/1002 20130101; A61F 2/958
20130101; A61M 2025/1059 20130101; A61M 25/10 20130101; A61M
25/1029 20130101; A61M 25/1034 20130101; A61M 25/10184 20131105;
A61M 25/1027 20130101 |
Class at
Publication: |
606/192 |
International
Class: |
A61M 029/00 |
Claims
1. A balloon catheter, comprising: An elongate, flexible tubular
body having proximal and distal ends; a first inflatable balloon on
the distal end of the tubular body; a first inflation lumen
extending through the tubular body and communicating with the first
inflatable balloon; a second inflatable balloon surrounding at
least a portion of the first inflatable balloon; a second inflation
lumen extending through the tubular body and communicating with the
second inflatable balloon; wherein the second inflatable balloon is
inflated to a first inflation profile by inflation of the first
balloon, and the second balloon is inflatable to a second profile
by inflation of the second balloon.
2-23. (canceled)
Description
[0001] The present application is a continuation of application
Ser. No. 08/742,437 filed on Oct. 30, 1996, which is a
continuation-in-part of copending application Ser. No. 08/640,533,
which is a continuation-in-part of copending application Ser. No.
08/572,783, the disclosures of which are hereby incorporated herein
by reference.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to catheters for insertion
into a body lumen. More particularly, the present invention relates
to "focal" balloon dilatation catheters for use in the vascular
system. As used herein, "focal" balloons are balloons which focus
or concentrate expansive energy at one or more predetermined
regions along the surface of the balloon.
[0003] Prior art vascular dilatation balloons on typical dilatation
catheters tend to fall into one of two broad classes. Most are
considered noncompliant balloons, formed from a generally
nondistensible material such as polyethylene. The perceived
advantage of the noncompliant balloons is that they exhibit a
substantially uniform exterior inflated profile which remains
substantially unchanged upon incremental increases in inflation
pressure. In theory, noncompliant balloons are advantageous because
they allow the introduction of increased inflation pressure to
break particularly calcified lesions, yet retain a predictable
inflated profile so that damage to the surrounding native lumen is
minimized.
[0004] Certain compliant balloons are also known in the art. A
compliant balloon is one which is able to grow in diameter in
response to increased inflation pressure. One difficulty with
compliant balloons, however, is that inflation within a difficult
lesion can cause the balloon to inflate around the plaque to
produce a generally hourglass-shaped inflated profile. This can
result in damage to the native vessel adjacent the obstruction,
while at the same time failing to sufficiently alleviate the
stenosis.
[0005] In use, both the compliant and noncompliant balloons are
generally inflated within a vascular stenosis to a rated inflation
pressure. At that pressure, the configuration of most balloons in
an unrestricted expansion is cylindrical. The balloon may be
subsequently inflated to a higher inflation pressure if that is
desirable in the clinician's judgment. However, the clinician has
no effective way to assess the actual inflated diameter of the
balloon in vivo based upon the unconstrained in vitro balloon
specifications. The in vivo expansion characteristics of the
balloon may track or deviate from the in vitro specifications
depending upon the morphology of the lesion and the appropriateness
of the selected balloon size. The clinician may know only generally
or not at all the degree of calcification of the lesion, the
symmetry or asymmetry, whether the lesion is soft or resilient, or
other variations which affect inflation. In applications where a
relatively accurate inflated diameter is desired, such as in
certain dilatations or in the implantation of tubular stents, the
clinician using prior dilatation balloons thus may not have enough
information about the dilatation characteristics of a particular
lesion to optimize the dilatation or stent implantation
procedure.
[0006] Therefore, there exists a need in the art for a vascular
dilatation catheter with a balloon which is able to grow
predictably in response to increased inflation pressure, and the
expansion of which the clinician can observe in real time in
comparison to a known diameter reference.
SUMMARY OF THE INVENTION
[0007] There is provided in accordance with one aspect of the
present invention a balloon catheter comprising an elongate
flexible tubular body and an inflatable balloon on the tubular
body. A proximal segment, a central segment and a distal segment on
the balloon are inflatable to a first inflated diameter at a first
inflation pressure, and the proximal and distal segment expand to a
second, greater inflated diameter at a second greater inflation
pressure. The central segment of the balloon remains at a diameter
which is less than the second diameter, at the second inflation
pressure. In one embodiment, the balloon additionally comprises at
least one expansion limiting band on the central segment to limit
inflation of the central segment of the balloon. Preferably, the
expansion limiting band limits expansion of the central segment to
no more than about the first inflated diameter.
[0008] In accordance with another aspect of the present invention,
there is provided a method of treating a site in a body lumen. The
method comprises the steps of providing a catheter of the type
having an elongate flexible tubular body and a dilatation balloon
on the body. A proximal segment, a distal segment and a central
segment of the balloon are inflatable to a first diameter at a
first inflation pressure; and the proximal and distal segments of
the balloon are inflatable to a second, greater diameter, at a
second, greater inflation pressure. The central segment remains
substantially at the first diameter at said second inflation
pressure.
[0009] The catheter is positioned within a body lumen so that the
balloon is adjacent a treatment site, and the balloon is inflated
to the first inflation pressure. At the first inflation pressure,
the proximal segment, the distal segment and the central segment
are inflated to no more than about the first inflation diameter,
The balloon is thereafter inflated to a second inflation pressure
so that the proximal and distal segments are expanded to the second
inflation diameter, while the central segment is simultaneously
restrained against further material radial expansion.
[0010] Optionally, the foregoing method comprises the additional
step of expressing a therapeutic or diagnostic media from the
central segment of the balloon to the site in the body lumen.
[0011] In accordance with a further aspect of the present
invention, there is provided a method of implanting a tubular graft
within a body lumen. The method comprises providing an elongate
flexible tubular body having an inflatable balloon thereon, the
balloon inflatable to a first diameter at a first inflation
pressure to produce a generally cylindrical balloon profile, and
proximal and distal portions of the balloon are additionally
inflatable to a second, larger diameter at a second, greater
inflation pressure. An expandable tubular graft is positioned on
the balloon, and the balloon is thereafter positioned within a body
lumen adjacent a treatment site.
[0012] The balloon is inflated to the first inflation diameter to
expand the tubular graft and thereafter inflation pressure is
increased to the second inflation pressure such that the proximal
and distal portions of the balloon inflate to the second, larger
diameter, to further expand the proximal and distal portions of the
tubular graft.
[0013] Further features and advantages of the present invention
will become apparent to one of skill in the art in view of the
Detailed Description of Preferred Embodiments which follows, when
considered together with the attached drawings and claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a schematic view of a preferred embodiment of a
variable diameter inflation catheter of one aspect of the present
invention, in the second inflation configuration.
[0015] FIG. 2 is a partial cross-sectional view of a preferred
embodiment of the variable diameter inflation catheter at a first
inflation profile.
[0016] FIG. 3 is a partial cross-sectional view of a preferred
embodiment of the variable diameter inflation catheter at a second
inflation profile.
[0017] FIG. 4 is a schematic view of the embodiment of FIG. 1,
shown in the first inflation configuration.
[0018] FIG. 5 illustrates a comparison of compliance curves between
the reference zones and the focal zone as a function of increased
inflation pressure in a differential compliance focal balloon of
the present invention.
[0019] FIG. 6 is a schematic illustration of a balloon of the
present invention having a relatively thin wall in the focal
section.
[0020] FIG. 7 is a cross sectional schematic illustration of a
fixed focal balloon catheter of the present invention.
[0021] FIG. 8 is a cross sectional view through a dual layer
balloon having a central compliant zone thereon.
[0022] FIG. 9 is a cross sectional view as in FIG. 8, with the
compliant zone in the expanded configuration.
[0023] FIG. 10 is a cross sectional schematic view of a balloon
profile having a focal zone and a tapered distal zone.
[0024] FIG. 11 is a schematic elevational view of a dual inflation
lumen catheter.
[0025] FIG. 12 is a cross sectional view through a dual layer
balloon having a unique inflation lumen for each layer.
[0026] FIG. 13 is a cross sectional view of a dual layer balloon as
in FIG. 12, in the focalized configuration.
[0027] FIG. 14 is a cross sectional view through a balloon similar
to that in FIG. 13, but with added delivery capability.
[0028] FIG. 15 is a cross sectional schematic illustration of a
balloon having a proximal and a distal lobe.
[0029] FIG. 16 is a cross sectional schematic illustration of a
dual balloon configuration.
[0030] FIG. 17 is a cross sectional illustration of a dual lobed
balloon adapted for delivery of media into the vessel.
[0031] FIG. 18 is a cross sectional view of a dual balloon
catheter, configured for delivery of media into the vessel.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0032] Referring to FIG. 1, there is disclosed a variable diameter
inflation catheter 10 in accordance with of one aspect of the
present invention. Catheters embodying additional features known in
the vascular dilatation art, such as implantable stents, drug
delivery, perfusion and dilatation features, or any combination of
these features, can be used in combination with the focal balloon
of the present invention as will be readily apparent to one of
skill in the art in view of the disclosure herein.
[0033] The catheter 10 generally comprises an elongate tubular body
12 extending between a proximal control end 14 and a distal
functional end 16. The length of the tubular body 12 depends upon
the desired application. For example, lengths in the area of about
120 cm to about 140 cm are typical for use in percutaneous
transluminal coronary angioplasty applications.
[0034] The tubular body 12 may be produced in accordance with any
of a variety of known techniques for manufacturing balloon-tipped
catheter bodies, such as by extrusion of appropriate biocompatible
plastic materials. Alternatively, at least a portion or all of the
length of tubular body 12 may comprise a spring coil, solid walled
hypodermic needle tubing, or braided reinforced wall, as is
understood in the catheter and guide wire arts.
[0035] In general, tubular body 12, in accordance with the present
invention, is provided with a generally circular cross-sectional
configuration having an external diameter within the range of from
about 0.03 inches to about 0.065 inches. In accordance with one
preferred embodiment of the invention, the tubular body 12 has an
external diameter of about 0.042 inches (3.2 f) throughout most of
its length. Alternatively, generally triangular or oval
cross-sectional configurations can also be used, as well as other
non-circular configurations, depending upon the number of lumen
extending through the catheter, the method of manufacture and the
intended use.
[0036] In a catheter intended for peripheral vascular applications,
the tubular body 12 will typically have an outside diameter within
the range of from about 0.039 inches to about 0.065 inches. In
coronary vascular applications, the tubular body 12 will typically
have an outside diameter within the range of from about 0.026
inches to about 0.045 inches. Diameters outside of the preferred
ranges may also be used, provided that the functional consequences
of the diameter are acceptable for the intended purpose of the
catheter. For example, the lower limit of the diameter for tubular
body 12 in a given application will be a function of the number of
fluid or other functional lumen, support structures and the like
contained in the catheter, and the desired structural
integrity.
[0037] Tubular body 12 must have sufficient structural integrity
(e.g., "pushability") to permit the catheter to be advanced to
distal arterial locations without buckling or undesirable bending
of the tubular body 12. The ability of the body 12 to transmit
torque may also be desirable, such as in embodiments having a drug
delivery capability on less than the entire circumference of the
delivery balloon. Larger diameters generally have sufficient
internal flow properties and structural integrity, but reduce
perfusion in the artery in which the catheter is placed. Increased
diameter catheter bodies also tend to exhibit reduced flexibility,
which can be disadvantageous in applications requiring placement of
the distal end of the catheter in a remote vascular location. In
addition, lesions requiring treatment are sometimes located in
particularly small diameter arteries, necessitating the lowest
possible profile.
[0038] As illustrated schematically in FIG. 1, the distal end 16 of
catheter 10 is provided with at least one inflation balloon 18
having a variable diameter. The proximal end 14 of catheter 10 is
provided with a manifold 20 having a plurality of access ports, as
is known in the art. Generally, manifold 20 is provided with a
guide wire port 22 in an over the wire embodiment and a balloon
inflation port 24. Additional access ports are provided as needed,
depending upon the functional capabilities of the catheter 10. The
balloon 18 can also be mounted on a rapid exchange type catheter,
in which the proximal guidewire port 22 would be unnecessary as is
understood in the art. In a rapid exchange embodiment, the proximal
guidewire access port is positioned along the length of the tubular
body 12, such as between about 4 and about 20 cm from the distal
end of the catheter.
[0039] Referring to FIGS. 2 and 3, the two-step inflation profile
of the inflation balloon 18 is illustrated. In FIG. 2, the balloon
18 is illustrated at a first inflation profile, in which in an
unconstrained expansion it exhibits a substantially cylindrical
central working profile. The dimensions in FIG. 2 are exaggerated
to illustrate a proximal segment 26 and a distal segment 28 which
are axially separated by a central focal segment 30. However, as
will be understood by one of ordinary skill in the art, when the
balloon 18 is inflated to the first inflation profile, the exterior
of the balloon 18 preferably exhibits a substantially smooth
cylindrical working profile.
[0040] In FIG. 3, the inflation balloon 18 is illustrated at a
second inflation profile. The proximal segment 26 and the distal
segment 28 of the balloon are separated by the central focal
segment 30 having a greater diameter. The configuration of FIG. 2
is achieved by inflating the balloon 18 to a first inflation
pressure, while the configuration of FIG. 3 is achieved by
increasing the inflation pressure to a second, higher pressure as
will be discussed below.
[0041] The details of one preferred embodiment of the variable
diameter inflation catheter 10 are discussed with reference to
FIGS. 2 and 3. Preferably, the tubular body 12 is provided with at
least a guidewire lumen 32 extending all the way through the
balloon 18, and an inflation lumen 34 extending into the proximal
end of the balloon 18.
[0042] In the illustrated embodiment, an inner balloon 36 is
disposed coaxially within an outer balloon 38. A substantially
nondistensible expansion limiting band 40 is disposed in between
the balloons 36 and 38 adjacent a proximal annular shoulder 42, to
limit the radial expansion of the balloon 18. Similarly, a distal
expansion limiting band 44 is disposed between the inner balloon 36
and outer balloon 38 adjacent a distal annular shoulder 46.
[0043] Expansion limiting bands 40 and 44 or other inflation
limiting structures can be provided in any of a variety of ways
which will be well-understood by one of skill in the art in view of
the disclosure herein. For example, in one embodiment, the bands 40
and 44 each comprise a tubular section of polyester, each having an
axial length of about 5 mm, a diameter of about 2.5 mm and a wall
thickness of about 0.0003 inches. Other generally nondistensible
materials such as nylon, polyamide, Kevlar fiber, cross-linked
polyethylene, polyethylene terephthalate and others, may be
utilized to accomplish the expansion-limiting effect.
[0044] The expansion limiting characteristics can be achieved by
the addition of a structure that is discrete from the balloon, or
by modifying the expansion properties of the balloon material
itself. For example, the balloon can be provided with zones of
differing wall thickness, or zones having different levels of cross
linking as will be discussed.
[0045] In general, the bands 40 and 44 must be of a sufficient
thickness or structural integrity for the particular material used
to substantially withstand inflation under the pressures normally
utilized in the context of dilatation catheters. However, the bands
40 and 44 are preferably thin enough to provide a substantially
smooth exterior surface of the balloon 18.
[0046] Preferably, as illustrated in FIGS. 2 and 3, the
expansion-limiting bands 40 and 44 are sandwiched between the inner
balloon 36 and the outer balloon 38. In alternative embodiments,
the expansion-limiting bands 40 and 44 or other inflation limiting
structures may be coated or mounted on the exterior surface of the
balloon 18, the interior surface of the balloon 18 or within the
wall of the balloon 18. Balloon 18 can be provided with two or more
layers as illustrated, or with only a single layer as will be
discussed.
[0047] The axial length of the bands 40 and 44 can be varied widely
depending upon the dimensions and the objectives of the catheter 10
as will be apparent to one of ordinary skill in the art. Further,
the proximal band 40 and distal band 44 need not be of similar
lengths. In general, however, some examples of dimensions which are
useful in the coronary angioplasty dilatation environment are
reproduced in Table 1 below, in which A represents the axial length
of the balloon 18 between proximal shoulder 42 and distal shoulder
46, B represents the axial distance between distal shoulder 46 and
transition point 48, and C represents the axial length of the
central focal segment 30. The dimensions of Table 1 are exemplary
only, and the present invention can be accomplished using a wide
variety of other dimensions as will be apparent to one of skill in
the art.
1TABLE 1 A B C 20 mm 5 mm 10 mm 30 mm 5 mm 20 mm 40 mm 5-10 mm
20-30 mm
[0048] The catheter 10 illustrated in FIGS. 2 and 3 can be
manufactured in accordance with any of a variety of techniques
which will be appreciated by one of ordinary skill in the art in
view of the disclosure herein. In the following disclosure,
particular materials and dimensions will be used as an example
only, and other dimensions and materials can be selected depending
upon the desired characteristics of the finished product.
[0049] In one particular method of manufacturing, a low density
polyethylene extrusion stock tube having an inside diameter of
about 0.018 inches and an outside diameter of about 0.043 inches is
used for the inner and outer balloons 36, 38.
[0050] The polyethylene stock tubing is cross-linked by exposure to
an electron beam in accordance with techniques well known in the
art. A test segment of the cross-linked stock tubing is free blown
up to 3.0 mm in diameter. If the cross-linked stock tubing can be
free blown to a diameter greater then 3.0 mm, the stock tubing is
cross-linked again and retested until the desired free blow
diameter is achieved.
[0051] The appropriately cross-linked stock tubing is then blown to
a diameter of 2.5 mm within a teflon capture tube (not shown) which
acts to mold the balloon to its desired first inflation diameter.
The teflon capture tube is a generally tubular body which has
approximately the same inside diameter as the desired inflation
diameter of the balloon. The teflon capture tube is heated by any
of a number of heating means such as electric coils or a furnace to
a temperature which is sufficient to mold the balloon to the
desired inflation diameter. In this case, the cross-linked
polyethylene balloon is preferably heated to a temperature of about
300.degree. F. The teflon chamber is then cooled to a temperature
below the softening temperature of the balloon. Once cooled, the
balloon is deflated and removed from the capture tube.
[0052] A section of inflation balloon material is thereafter
stretched with application of heat to neck down the proximal and
distal ends 37, 39 to a thickness of about 0.001 inches and a
diameter which relatively closely fits the portion of the tubular
catheter body 12 to which it is to be sealed.
[0053] The balloon is then attached to the tubular body 12 by any
of a variety of bonding techniques known to one of skill in the art
such as solvent bonding, thermal adhesive bonding or by heat
shrinking/sealing. The choice of bonding techniques is dependent on
the type of balloon material and tubular body material used to form
the catheter 10.
[0054] In one particular method of manufacture, inner balloon 36
and outer balloon 38 are attached to the catheter body 10. The
proximal necked end 37 of the inner balloon 36 is heat sealed
around the catheter body 12. The distal necked end 39 of the inner
balloon 36 is thereafter heat sealed around the distal end 16 of
the catheter body 12. In general, the length of the proximal end 37
and the distal end 39 of the inner balloon 36 which is secured to
the catheter body 12 is within the range of from about 3 mm to
about 10 mm, however the proximal and distal balloon necked ends
37, 39 are as long as necessary to accomplish their functions as a
proximal and distal seal.
[0055] Expansion limiting bands 40 and 44 are respectively
positioned at the proximal segment 26 and the distal segment 28 of
the inner balloon 36 and may be bonded or otherwise secured to the
inner balloon 36. The outer balloon 38 is thereafter be mounted to
the catheter body 12 in a similar manner as the inner balloon 36,
following "necking down" of the proximal and distal axial ends of
the outer balloon 38 by axial stretching under the application of
heat. The outer balloon 38 is advanced axially over the inner
balloon 36 and the expansion limiting bands 40 and 44. The outer
balloon 38 may thereafter be bonded to the inner balloon 36, and to
the expansion limiting bands 40 and 44 by any of a variety of
bonding techniques such as solvent bonding, thermal adhesive
bonding or by heat sealing also depending on the type of balloon
material used. Alternatively, the expansion limiting bands are
simply entrapped between the balloons without any bonding or
adhesion.
[0056] In a preferred embodiment, the inner balloon and the outer
balloon 36, 38 are both cross-linked polyethylene balloons which
are difficult to bond together using conventional solvents. If
sealing is desired, the inner balloon 38 and the outer balloon 38
are heat sealed together as described below. In another embodiment,
the inner balloon 36 and outer balloon 38 are secured together
through the use of a UV-curable adhesive.
[0057] The inner balloon 36 and the outer balloon 38, once mounted
to the catheter body 12, can be heat sealed together in a heating
chamber (not shown) such as a Teflon capture tube. Inner balloon 36
and outer balloon 38 are inflated in the chamber until the inner
balloon and the outer balloon inflate to the first inflation
diameter. The heating chamber is heated by any of a number of
heating means such as electric coils or a furnace to heat air to a
temperature which is sufficient to bond the two balloons 36, 38
together. In this case, the cross-linked polyethylene balloons are
preferably heated to a temperature of about 300.degree. F. within
the chamber which causes both balloons 36, 38 to seal together to
form a double walled variable diameter inflation balloon 18. The
chamber is then cooled to a temperature below the softening
temperature of the inner and outer balloons 36 and 38. Once cooled,
the variable diameter balloon 18 is deflated and the catheter 10 is
removed from the chamber.
[0058] It will be apparent to one of skill in the art, that it is
possible to attach the inner balloon 36 and the outer balloon 38 to
the catheter body 12 without adhesively bonding or otherwise
securing the two balloons together. In this case, the two balloons
will respond to the applied inflation pressure with the inner
balloon 36 forcing the outer balloon 38 to simultaneously inflate
both balloons 36, 38. The expansion limiting bands 40 and 44 can be
merely sandwiched between the inner balloon 36 and the outer
balloon 38 and do not in this embodiment need to be bonded to
either balloon.
[0059] The variable diameter balloon design of the present
invention can also be accomplished with a single layer balloon or a
double layer balloon without the inclusion of additional expansion
limiting bands. This is accomplished by decreasing the relative
compliance of the zones of the balloon that are intended to remain
at the first inflated diameter. Alternatively, the compliance of
the focal section can be increased relative to that of the
reference zones.
[0060] For example, polyethylene extrusion stock is cross-linked to
3.0 mm and blown into a mold of a diameter of about 2.5 mm as
described above to form a balloon. Balloon stock can be crosslinked
either before or after mounting on the catheter, and in either the
inflated or deflated state. The proximal and distal segments 26, 28
of the balloon on the catheter 10 are masked such as with steel
clamps or other masks known in the art to block electron beam
penetration, leaving the central segment 30 of the balloon exposed.
The central segment 30 of the balloon 18 is exposed again to an
electron beam source to be further cross-linked at the 2.5 mm
diameter. Balloons manufactured in this manner have been found to
exhibit a relatively highly compliant central zone and relatively
less complaint axial end zones in a manner that achieves the
two-step dilatation as illustrated in FIGS. 2 and 3.
[0061] Single layer balloons having the differential compliancy
characteristics described above can also be provided using other
balloon materials such as polyethylene terephthalate (PET). For
example, a one piece single layer PET balloon can be provided with
a thinner wall in the focal section compared to the one or two
reference sections of the balloon. FIG. 6 discloses a schematic
illustration of a balloon 50 in accordance with this aspect of the
present invention. The balloon 50 defines an interior space 51 for
containing inflation media as is understood in the art. The balloon
50 generally comprises a distal neck portion 52 and proximal neck
portion 54 for securing the balloon 50 to the catheter. A working
length of the balloon 56 extends between proximal shoulder 55 and
distal shoulder 57.
[0062] The working length 56 of the balloon 50 is provided with a
proximal reference zone 62 and a distal reference zone 58,
separated by a focal zone 60. As has been discussed in connection
with previous embodiments, the balloon 50 can alternately be
provided with only a single reference zone either 58 or 62,
together with the focal zone 60. Preferably, however, both proximal
and distal reference zones 62 and 58 will be utilized with a
central focal zone 60.
[0063] The thickness of at least a portion of the balloon wall in
the area of focal zone 60 is thinner than the wall thickness in the
reference zones 62 and 58.
[0064] In one embodiment of the single wall focal balloon of the
present invention, the balloon comprises PET. The balloon has a
working length of about 20 mm, and the proximal and distal
reference zones 62 and 58 each have a length of about 5 mm. The
focal zone 60 has a length of about 10 mm. The first inflated
diameter at 8 ATM is about 3.0 mm, and the focal section inflates
in vitro to about 3.5 mm at 16 ATM. The wall thickness in the area
of reference zones 62 and 58 is about 0.001 inches, and the wall
thickness in the area of focal zone 60 is about 0.0007 inches.
[0065] Whether the balloon comprises PET or other balloon materials
known in the art, a thinner focal section compared to the thickness
at the reference section can be provided using a variety of
techniques. For example, the PET balloon can be exposed to heat and
stretched in the center portion to provide a relatively thinner
wall than the end reference portions. Alternatively, the balloon
can be heated at its ends to shrink the balloon thereby increasing
the thickness of the material in the regions exposed to heat.
[0066] Thinning a portion of the wall of the balloon by stretching
the material can be accomplished in any of a variety of ways that
will be apparent to those of skill in the art, in view of the
disclosure herein. One method of reducing the wall thickness in the
region of the focal zone involves an axial elongation of the
tubular balloon stock under the application of heat. In general,
the present inventor has found that the percent reduction in wall
thickness is roughly equivalent to the percent axial elongation of
the tubular stock. Thus, the tube stock is axially elongated a
sufficient distance to achieve the desired reduction in wall
thickness.
[0067] In one application of the invention, a molded PET balloon
having a wall thickness of about 0.001 inches was axially elongated
a sufficient distance to reduce the focal zone thickness to about
0.0007 inches. A molded PET balloon having a wall thickness of
about 0.0008 inches was axially elongated by 40% to produce a wall
thickness of about 0.0005 inches.
[0068] In one application of the method of the invention, a length
of tubular polymeric stock is provided. The stock may be cut to a
useful working length, such as 10-20 centimeters. Excess stock
length following the elongation process will be trimmed prior to
mounting of the balloon on the catheter shaft as will be understood
by those of skill in the art.
[0069] A 15 cm length of PET balloon tubing having a wall thickness
of about 0.0010 inches and an inflated outside diameter of about
3.0 mm was clamped at or near each end in a device configured to
apply an axially stretching force to the tubing. Prior to closing
one of the clamps, a needle was advanced through the open end of
the tubing so that the tubing can be pressurized following
clamping. Following clamping, the tubing was inflated under a
pressure of about 100 psi, and axial tension in the area of about 1
lb. was applied.
[0070] The foregoing setup for a 3 mm balloon was accomplished
inside of a 3 mm capture tube. First and second aluminum heat sinks
were thermally coupled to the capture tube, and spaced about 5 mm
apart. A hot air heater having a length of about 5 mm in the axial
tube direction was positioned in between the heat sinks and
advanced towards the capture tube to heat the capture tube. The
heat sinks assist in localizing the region of the tubing stock
which will be heated by the heater, as will be understood by those
of skill in the art.
[0071] Upon reaching a temperature of about 200.degree. F., the
tube stock begins to stretch under the axial tension. The axial
length of travel of the stretching clamps is preferably limited to
provide a predetermined limit for the percentage axial elongation.
In one application of the invention, the 5 mm heated section grew
to about 5 or 7 mm in axial length following a 20%-40% increase in
the distance between the clamps. Any of a variety of modification
to the foregoing procedure can be readily envisioned by those of
skill in the art. For example, alternate sources of heat such as
forced air heating, infra red, electrical coil, and others known in
the art can be used. In addition, stretching can be accomplished
through any of a variety of physical setups, which can be readily
assembled by those of skill in the art. Stretching without the
application of heat, such as by cold rolling or cold forming a
portion of tubular stock may also provide an acceptable thinning of
the balloon wall for certain types of balloon materials.
[0072] Subject to the pressure retention characteristics of bonds
between dissimilar balloon materials, the balloon can alternatively
be provided with a relatively more compliant material in a focal
section, and a relatively less compliant material in a reference
section. Balloons having a combination of materials having
different compliancies can be manufactured, for example, using two
extrusion heads which alternately drive balloon material through a
single orifice. Any of a variety of material pairs may be used,
such as nylons of different hardness, PET and PE, and others that
can be selected by those skilled in the art. As a further
alternative, the focal section can be formed from an entirely
different balloon which is positioned adjacent a single reference
balloon or positioned in between two reference balloons to produce
a balloon having some of the characteristics of the focal balloon
of the present invention.
[0073] Balloons 18 made in accordance with the design illustrated
in FIGS. 2 and 3 have been found to exhibit the inflation pressure
profile illustrated in Table 2.
2TABLE 2 CENTRAL SEGMENT PROXIMAL AND DISTAL PRESSURE DIAMETER
SEGMENT DIAMETER 6 atm 2.5 mm 2.5 mm 7 atm 2.6 mm 2.5 mm 8 atm 2.7
mm 2.5 mm 9 atm 2.8 mm 2.5 mm 10 atm 2.9 mm 2.6 mm 11 atm 3.0 mm
2.6 mm 12 atm 3.1 mm 2.7 mm 13 atm 3.2 mm 2.7 mm 14 atm 3.2 mm 2.7
mm
[0074] The inflation pressure profile of the variable diameter
inflation balloon 18 illustrated in Table 2 provides an example of
the manner in which a balloon 18 made in accordance with the
foregoing method is inflated with the application of increased
pressure. Initially, the central segment 30 and the proximal and
distal segments 26, 28 of the balloon 18 inflate together in vitro
as the pressure increases. When the pressure reaches 6 ATM, for
example, the diameter of the proximal and distal segments 26, 28
and the central segment 30 of the balloon all remain at about 2.5
mm. At 11 ATM, the diameter of the central segment 30 of the
balloon 18 has grown to about 3 mm while the proximal and distal
segments 26, 28 remained inflated to the first diameter of
approximately 2.5 mm. The diameter of the central section 30 of the
balloon 18 will continue to increase at least in vitro until the
burst pressure of the balloon 18 is reached. In one prototype, the
burst pressure was approximately 20 ATM at normal body
temperature.
[0075] Both the first inflation diameter and the second inflation
diameter can also be varied depending upon the desired catheter
characteristics as will be understood by one of ordinary skill in
the art. In a preferred embodiment, a first inflated diameter of
the catheter for coronary angioplasty applications is approximately
2.5 mm. Upon an increase of pressure, this diameter grows to a
second inflated diameter of approximately 3 mm in the central focal
segment 30. In general, balloons can be readily constructed having
a difference between the first inflation diameter and second
inflation diameter anywhere within the range of from about 0.1 mm
up to 1.0 mm or more, depending upon the elastic limits of the
material from which the balloon was constructed. Typically,
coronary angioplasty dilatation balloons will have a first diameter
within the range of from about 1.5 mm to about 4.0 mm. Typical
balloons for use in peripheral vascular applications will have a
first inflation diameter within the range of from about 2 mm to
about 10 mm.
[0076] Dilatation balloons can readily be constructed in accordance
with the present invention in which entire length of the balloon
from, for example, proximal shoulder 42 to distal shoulder 46 (FIG.
2) is variable from a first inflated diameter to a second larger
inflated diameter in response to increasing pressure.
Alternatively, balloons in accordance with the present invention
can readily be constructed in which a proximal portion of the
balloon is compliant so that it can grow in response to increased
pressure, while a distal portion of the balloon has a fixed
inflated diameter. This configuration may be desirable, for
example, when the native vessel diameter is decreasing in the
distal catheter direction. Positioning the catheter so that the
compliant portion is on the proximal (larger diameter) portion of
the vessel may minimize damage to the vessel wall in certain
applications. Alternatively, the compliant segment can readily be
positioned on the distal end of the balloon with a substantially
fixed inflated diameter segment on the proximal end of the
balloon.
[0077] A variable diameter balloon 18 made in accordance with the
foregoing designs has been found to benefit certain conventional
percutaneous transluminal coronary angioplasty (PTCA) procedures.
In accordance with the method of the present invention, the
variable diameter balloon 18 is percutaneously advanced and
positioned such that the central segment 30 of the balloon 18 is
adjacent a vascular treatment site. Generally, the treatment site
is a stenosis such as due to a plaque or thrombus. The variable
diameter balloon 18 is inflated to a first inflation profile to
begin dilation of the stenosis. Preferably, the first inflation
profile is achieved by applying up to about 6 ATM of pressure to
the balloon 18. At the first inflation profile, the entire balloon
is inflated to the inner diameter of the vessel, thus restoring
patency to the vascular lumen. In one embodiment, the variable
diameter balloon 18 is inflated to a first inflation diameter, of
about 2.5 mm, at an inflation pressure of 6 ATM. The first
inflation diameter is preferably about the native diameter of the
vessel.
[0078] As additional pressure is applied to the variable diameter
balloon 18, a second inflation profile is achieved wherein the
central segment 30 of the balloon 18 expands beyond the diameter of
the first inflation profile to a second inflation diameter, while
the proximal segment 26 and the distal segment 28 remain at or
substantially at the first inflation diameter. As the pressure
applied to the variable diameter balloon 18 increases, the diameter
of the central segment 30 of the balloon 18 extends past the native
diameter of the vessel to the second inflation diameter. Utilizing
this method, and depending upon the balloon size selected, the
stenosis is compressed to a point which is beyond the native
diameter of the vessel. In a preferred embodiment, at an applied
pressure of 11 ATM the diameter of the central segment 30 of the
balloon 18 at the second inflation diameter is 3 mm and the
diameter of the proximal end 26 and the distal end 28 at the first
inflation diameter is approximately 2.5 mm. Second inflation
diameters in between the first inflation diameter and the maximum
inflation diameter can be readily achieved by controlling inflation
pressure, as illustrated for one embodiment in Table 2, above.
[0079] After the stenosis is compressed to or beyond the native
diameter of the vessel, the balloon is evacuated and the catheter
withdrawn. Alternatively, if desired, the pressure is reduced until
the balloon 18 resumes the first inflation profile. At this point,
the balloon 18 may be held at the first inflation diameter for
short periods to continue to maintain patency of the lumen if short
term rebound is a concern. This post dilatation step is preferably
accomplished using a catheter having perfusion capabilities.
Finally, the remaining pressure applied to the balloon 18 is
reduced causing the variable diameter balloon 18 to deflate. The
catheter is then extracted from the vessel utilizing conventional
PTCA procedures.
[0080] The "focal" or "differential compliance" balloon of the
present invention provides important real time diagnostic
information about the lesion being treated. In a balloon having one
or more noncompliant or substantially noncompliant zones such as
proximal segment 26 and distal segment 28 and a central focal
segment 30, (FIG. 2) inflation within a lesion will proceed through
a series of discreet phases. The phases can be visually
differentiated by observing the balloon fluoroscopically and
comparing the apparent diameter of the central section with the
diameter of the one or more substantially noncompliant zones. The
substantially noncompliant zones may be considered reference zones
for present purposes.
[0081] When the balloon 18 is inflated within a lesion, the
reference zone will normally be positioned proximally or distally
of the lesion and the central zone will be centered within the
lesion. As balloon inflation begins, the overall balloon may take
on a "dog bone" shape with the central portion radially inwardly
restrained by the lesion. As inflation pressure is increased, the
central section will tend to expand until the balloon has assumed
an overall generally cylindrical profile. At a certain higher
pressure, the balloon will focalize, such that the central region
has reached its second, larger inflated diameter. By observing the
first pressure at which the balloon assumes a generally cylindrical
configuration and the second higher pressure at which the balloon
focalizes, the clinician can learn important information about the
morphology of the lesion.
[0082] For example, in a balloon rated 3.0 mm at 6 atmospheres, the
reference zone may grow to 3.2 mm at 11 atmospheres. The focal
section will grow to 3.0 mm at 6 atmospheres, and, in a healthy
artery, should grow to 3.5 mm at 11 atmospheres. If there has been
no focalization at 11 atmospheres, the clinician will know that the
lesion is highly calcified or is otherwise highly resistant to
expansion. The pressure can then be gradually increased up to a
maximum pressure which approaches the burst pressure, and the
pressure at which focalization is finally visualized will reveal
information about the degree of calcification or other information
about the lesion.
[0083] Thus, there is provided in accordance with the present
invention a method of obtaining characterizing information about a
lesion. The characterizing information is obtained by positioning a
differential compliance balloon in the artery such that a central
focal section is positioned within the lesion. The balloon is
inflated to a first inflation pressure such that the balloon
achieves a "dogbone" configuration with the lesion. The clinician
preferably notes that first pressure. The pressure is increased
until the balloon achieves a generally cylindrical exterior
configuration. The pressure at which the substantially cylindrical
configuration is achieved is preferably noted. The pressure in the
balloon is increased further until focalization of the central
section is achieved, and the focalization pressure is noted. One or
more of the noted pressures may be compared to other information
concerning the same patient or against reference data to assess the
nature of the lesion. Since the balloon can be readily
fluoroscopically visualized, the clinician receives real time
information about the size of the inflation balloon merely by
visually comparing the focal section with the reference section.
If, at a particular pressure, the balloon is "straight across"
(i.e. has not focalized) the clinician can look at the reference
chart for the balloon or rely upon experience to assess the
diameter of the vessel at the treatment site.
[0084] In accordance with another aspect of the present invention,
there is provided a method of interactive angioplasty using the
differential compliance balloon of the present invention. In
general, the interactive angioplasty method involves inflating the
balloon to a first inflation pressure, which should produce a first
inflation profile for a particular expected lesion morphology. If
the profile of the balloon at the first inflation pressure is
different than the expected first inflation profile, the clinician
will know that the lesion morphology may be different than
anticipated. The clinician can thus responsively change the course
of treatment, such as by removing the catheter and replacing it
with a different one.
[0085] For example, if a highly calcified or fibrotic lesion is
expected and the first inflation pressure produces a substantially
cylindrical balloon rather than a dogbone shaped balloon, the
clinician may determine that the balloon selected was too small or
the lesion was not calcified or fibrotic as expected. That balloon
catheter may be withdrawn and a catheter having a larger balloon
thereafter positioned in the lesion. If the expected degree of
inflation at the focal zone (compared, for example, to the
reference zone) fails to occur at the expected inflation pressure,
the clinician may alternatively elect to increase the inflation
pressure, thereby exerting a greater force on the lesion.
[0086] Alternatively, lesion morphology information obtained by
comparing the expected inflation profile at a given pressure stage
with the actual inflation profile may cause the clinician to seek
alternate treatment, such as drug therapy, surgery, or other
techniques that may be available at the time. More rapid
progression than expected from dogbone to cylindrical to focalized
inflation may indicate the presence of soft placque or of a
thrombosis, and measures can be taken in response to minimize the
risk of over dilatation or embolization. These measures may include
drug therapy such as local administration of streptokinase or TPA,
or other measures such as atherectomy, laser therapy or
stenting.
[0087] One of the advantages of the interactive angioplasty of the
present invention is that the clinician can alter the course of
treatment during the procedure, in response to information obtained
during the procedure about lesion morphology or progression of the
procedure. For example, if the balloon fails to focalize at the
pressure previously expected to produce focalization, depending
upon other circumstances of the patient, the clinician may
determine that further dilatation of the lesion will produce an
undesirable dissection of the artery, and a different treatment may
be indicated. Alternatively, the clinician may elect to simply
increase the inflation pressure until focalization occurs, or
substitute a different balloon having a different inflation
diameter or capable of sustaining a greater inflation pressure.
[0088] At each of the reference points identified previously
herein, such as the dogbone profile, the cylindrical profile, and
the focalized profile, any deviation from the expected pressure to
achieve that profile can thus be noted by the clinician and used to
assess the course of further treatment. The interactive angioplasty
method of the present invention can be accomplished both in the
context of balloon dilatation and also in the context of
implantation and or sizing of an intervascular prosthesis
(stent).
[0089] Pressure response data for a series of exemplary balloons
manufactured in accordance with the present invention using
techniques described previously herein is provided in Table III
below. The compliance curves for a reference zone and a focal zone
of a differential compliance balloon rated for 3.5 mm at 6
atmospheres are illustrated in FIG. 5.
3TABLE III EFFECT OF INCREASED PRESSURE ON BALLOON DIAMETER Balloon
11 ATM 14 ATM 16 ATM 3.0 mm Reference Zone 3.2 mm 3.2 mm 3.3 mm
Focal Zone 3.5 mm 3.5 mm 3.5-3.7 mm 3.5 mm Reference Zone 3.7 mm
3.7 mm 3.8 mm Focal Zone 4.0 mm 4.0 mm 4.0-4.2 mm 4.0 mm Reference
Zone 4.2 mm 4.2 mm 4.3 mm Focal Zone 4.5 mm 4.5 mm 4.5-4.7 mm
[0090] As exemplified in Table III, the reference zones on a
particular balloon are expected to have a predetermined diameter at
certain pressures. For example, the reference zones on a 3.0 mm
balloon are expected to inflate to 3.2 mm at 11 ATM. If the balloon
appears to be "straight across" at 11 ATM, the clinician knows that
the focal section and therefore the lesion has been inflated to 3.2
mm. If the balloon has focalized, the clinician knows that the
lesion has been inflated to 3.5 mm by referring to a look up table
containing the balloon specifications. If focalization does not
occur until a higher pressure such as 14 ATM has been reached, the
clinician still knows that the lesion has been inflated to 3.5 mm,
but also knows that the lesion was relatively calcified or
fibrotic.
[0091] The present interactive angioplasty invention thus enables
the clinician to take into account the difference in balloon
inflation characteristics between the in vitro and in vivo
environments. Balloons in vitro exhibit a predictable inflation
response to pressure. Balloon inflation in vivo, however, can be
quite different from the balloon rating, and also from lesion to
lesion, as a result of the differences in vessel wall thickness,
lesion morphology and other characteristics that affect the
resistance to radial expansion in the area of the target lesion. By
providing reference information such as the inflated diameter of
the reference and focal zones of a balloon at each of a series of
pressures, the clinician can determine the actual diameter of the
balloon in the focal zone by observing the balloon in either of the
"straight across" or focalized inflation profiles.
[0092] The differential compliance balloon of the present invention
is also particularly suited for the implantation and or sizing of
intravascular stents. For example, in a 3.2 mm vessel, it may be
desirable to dilate a stent to 3.5 mm inside diameter since some
stents tend to recoil in vivo. If the balloon is inflated up to 10
ATM with no focalization, the clinician knows to increase the
pressure until a focal section becomes apparent. When the focal
section has become apparent, the clinician will know that the
inside diameter of the stent has been appropriately inflated to 3.5
mm.
[0093] In accordance with a further aspect of the present
invention, there is provided a method of implanting a tubular stent
within a body lumen. Tubular stents of the type adapted to be
carried to a vascular site on a balloon catheter, and for expansion
from a first insertion diameter to a second implanted diameter are
well-known in the art.
[0094] In accordance with the method of implanting a tubular stent,
an expandable stent is positioned about the deflated balloon of a
variable diameter balloon catheter in accordance with the present
invention. The balloon is thereafter percutaneously inserted into
the vascular system and transluminally advanced to position the
stent at the treatment site. The balloon is thereafter inflated to
at least a first inflation configuration, wherein the balloon
exhibits a substantially cylindrical profile throughout its axial
length. Thereafter, the balloon is optionally inflated to a second
inflation profile, thereby inflating at least a portion of the
stent to a second, greater diameter. Depending upon the etiology of
the underlying condition, the central region of the stent may
preferentially be inflated to a larger diameter than either of the
axial ends of the stent. Alternatively, the axial length of the
stent is selected to approximately equal the axial length of the
focal zone on the inflation balloon. In this manner, the inflation
balloon within the stent is expandable to a diameter slightly
larger than the native diameter of the adjacent vessel. This
permits subsequent overgrowth of endothelium along the interior
wall of the stent while still leaving a lumen having an interior
diameter within the stent approximately equal to the native
diameter of the lumen adjacent the stent.
[0095] In accordance with a further aspect of the present
invention, the variable diameter balloon is utilized to "tack down"
a previously positioned tubular stent. In accordance with this
aspect of the present invention, a tubular stent is identified
within a body lumen. The focal balloon is positioned within the
stent in accordance with conventional PTCA procedures, and the
balloon is inflated so that the central, focal section enlarges the
diameter of at least a first portion of the stent. The balloon is
thereafter reduced in diameter, and, preferably, repositioned
within a second region within the stent and then reinflated to
expand at least the second region of the stent. Expansions of this
type can be repeated until the stent has been expanded as desired.
The balloon is thereafter evacuated and removed from the
patient.
[0096] In accordance with a further aspect of the present
invention, there is provided a method of percutaneous transluminal
angioplasty in which multiple lesions of differing sizes are
dilated without removing the catheter from the body. In accordance
with this aspect of the present invention, the variable diameter
balloon is positioned within a first stenosis in accordance with
conventional PTCA techniques. The balloon is dilated to a
sufficient diameter to restore patency to the vascular lumen. The
balloon is thereafter deflated, and repositioned within a second
stenosis in the vascular system. The balloon is inflated to restore
patency of the vessel in the region of the second stenosis.
Optionally, the balloon may be deflated, and repositioned within a
third stenosis in the body lumen. The balloon is then inflated to a
sufficient diameter to restore patency in the body lumen in the
region of the third stenosis. Four or more lesions can be treated
seriatim in this manner.
[0097] Preferably, the balloon is inflated to a first diameter in
the first stenosis, and to a second, different diameter, in the
second stenosis. In this manner, multiple dilatations at different
diameters can be accomplished utilizing the balloon of the present
invention. This method is accomplished by supplying a first
inflation pressure to the balloon while the balloon is positioned
in a first position in the vascular system, and thereafter
supplying a second pressure to the balloon when the balloon is in a
second position in the vascular system. In accordance with the
previous disclosure herein, each of the first and second inflation
pressures is selected to achieve a preselected inflation diameter
of the balloon.
[0098] A number of the advantages of the interactive angioplasty
methods and stent implantation and sizing methods of the present
invention can also be accrued through the use of an alternate
embodiment of the balloon of the present invention as illustrated
in FIG. 7. Referring to FIG. 7, there is disclosed a fixed focal
balloon 64. By "fixed" focal balloon, it is meant that the balloon
assumes a stepped configuration in its initial in vitro inflated
profile. Increased inflation pressure beyond the pressure necessary
to achieve the initial stepped inflation profile does not
appreciably change the relative proportionality of the profile from
its initial stepped configuration.
[0099] The stepped configuration is characterized by a difference
in diameter between at least one reference zone and a focal zone,
preferably on the same balloon. The fixed focal balloon of the
present invention can be constructed using either relatively
compliant or relatively noncompliant materials, with the resulting
characteristics that will be readily apparent to those of skill in
the art in view of the disclosure herein. Preferably, the fixed
focal balloon comprises polyethylene terephthalate.
[0100] The embodiment of the fixed focal balloon 64 illustrated in
FIG. 7 has a central focal zone and a proximal as well as a distal
reference zone. However, the present inventors also contemplate
fixed focal balloons in which either the proximal reference zone or
the distal reference zone is omitted. These embodiments include
only a single reference zone and a single focal zone. The reference
zone may be positioned either proximally or distally of the focal
zone.
[0101] For example, in one two segment embodiment of the present
invention, a proximal segment on the balloon is inflatable to a
greater diameter than a distal segment. In general, the proximal
segment will inflate to a generally cylindrical configuration in an
unconstrained inflation. A transition zone is disposed at the
distal end of the proximal segment. In the transition zone, the
diameter of the balloon steps down to the smaller inflated diameter
of the distal segment. The axial lengths and diameters of the
proximal and distal segments can vary widely depending upon the
intended use of the balloon. In one application, the balloon is
used to size or implant two stents positioned end to end in a
vessel. The stents may comprise a pair of 15 mm length stents or 20
mm length stents or otherwise as may be desired. For this
application, the balloon may have an overall length of from about
20 mm or 30 mm to about 40 mm or greater. In one 30 mm balloon, a
proximal segment is approximately 15 mm long and has an inflated
diameter of about 3.5 mm. At the distal end of the proximal segment
is a transition zone which will be generally be less than 1 or 2 mm
in length and preferably about a 1/2 mm in length. Distally of the
transition zone is a second segment approximately 15 mm in length
and having an inflated diameter of about 3.0 mm. Alternate pairs of
proximal and distal segment inflated diameters may also be utilized
as will be appreciated by those of skill in the art. In general,
the difference in diameter between the proximal and distal segments
will be within the range of from about 0.2 mm to about 1 mm, and,
preferably, will be about 0.5 mm. Proximal and distal segment
diameter and pairs for balloons believed useful by the present
inventor include 4.0/3.5 mm, 3.5/3.0 mm, 3.0/2.5 mm. Proximal and
distal balloon zone lengths are preferably approximately equal in a
given balloon, e.g., 20 mm/20 mm in a 40 mm balloon, although
dissimilar zone lengths may be desirable in particular specialty
applications.
[0102] As a further alternative, the balloon is provided with three
stepped diameters in the inflated profile. In a 30 mm balloon, for
example, a proximal 10 mm section inflates to a first diameter, an
intermediate 10 mm section inflates to a second diameter and a
third 10 mm section inflates to a third diameter. Preferably, the
first, second and third diameters decrease in the distal direction.
The diameters of adjacent sections may be separated by 0.5 mm, 0.25
mm, or other differential as may desired for the intended
application. Thus, in an exemplary balloon, the first diameter is
3.5 mm, the second diameter is 3.0 mm and the third diameter is 2.5
mm. In an alternate example, the first diameter is 3.5 mm, the
second diameter is 3.25 mm and the third diameter is 3.0 mm.
Similar gradations from about 2 mm up through about 4.5 mm for
coronary applications, and up to 8 or more millimeters for other
applications may be used.
[0103] Any of the preceding multizone balloons, particularly the
two zone and three zone balloons can be utilized to implant or size
a single "long" stent or expandable graft. For present purposes,
long stents will have an axial length of greater than about 20 mm,
and could have any of a variety of lengths such as 25, 30, 35, 40,
45, 50, 55, 60 mm or longer. Corresponding balloon lengths are also
contemplated. Stent and balloon lengths intermediate the foregoing
dimensions may also be utilized, as will be appreciated by those of
skill in the art. Two or three or four or more axially adjacent
stents may also be implanted or sized using the catheters described
herein.
[0104] Any of the balloon catheter designs described herein may be
utilized in the method of implanting a tubular stent, the method of
sizing a previously implanted stent, or simultaneously implanting
and sizing tubular stents (which term is intended to include grafts
throughout). The balloon catheters disclosed herein are also useful
in the methods of simultaneously implanting and/or sizing multiple
stents.
[0105] Alternatively, the proximal and distal zones in a three zone
balloon may be inflatable to the relatively larger diameter, while
the central zone is inflated to the smaller, reference diameter.
This embodiment may be considered to have a proximal and a distal
focal zone and a single central reference zone. These and
additional variations are illustrated in FIGS. 8-18, discussed
infra. The desirability of one combination over another will be
governed by the requirements for a particular balloon dilatation or
stent or graft implantation procedure as will be apparent to those
of skill in the art in view of the disclosure herein.
[0106] Referring to the embodiment illustrated in FIG. 7, the fixed
focal balloon 64 is provided with a proximal reference zone 66, a
central focal zone 68 and a distal reference zone 70. The relative
lengths of each of these zones may vary considerably depending upon
the intended use of the balloon. In general, any of the dimensions
of the balloon, both in terms of diameters and lengths as well as
other catheter dimensions, may be the same as those disclosed in
connection with other embodiments previously disclosed herein. In
one particular application, the focal zone 68 has an axial length
of 10 millimeters, and each of the proximal zone 66 and distal zone
70 has an axial length of about 5 millimeters. At 8 atmospheres
inflation pressure, the proximal reference zone 66 has an outside
diameter of about 3 millimeters, and the focal zone 68 has an
outside diameter of about 3.4 millimeters. The same balloon at 18
atmospheres inflation pressure has an outside diameter of about 3.1
millimeters in the proximal reference zone 66 and an outside
diameter of about 3.5 millimeters in the focal zone 68. That
particular balloon was constructed from PET, having a wall
thickness of about 0.0006-0.0008 inches.
[0107] Depending upon the desired clinical performance of the
balloon, the relative expansion characteristics of the reference
zone compared to the focal zone can be varied. For example,
although the focal section will normally retain a larger inflated
diameter than the reference zone, the reference zone may grow in
response to an increase in inflation pressure a greater amount than
the focal zone. In one PET balloon, having a wall thickness in the
range of from about 0.0006 to about 0.0008 inches, the growth of
the reference zone upon an increase in inflation pressure from 8 to
18 atmospheres was about 0.2610 millimeters. The growth in the
focal zone over the same pressure increase was about 0.1457
millimeters. It may alternatively be desired to achieve a greater
growth in the focal zone compared to the reference zone, or an
equal growth in each zone as a function of increased pressure.
Optimizing the growth response to increased pressure of the focal
zone relative to the reference zone for any particular intended
application can be accomplished by the exercise of routine skill in
the art in view of the disclosure therein.
[0108] The fixed focal balloon 64 further comprises a first
transition 72 which steps the diameter of the balloon up from the
diameter of the catheter shaft 74 to the diameter of the proximal
reference zone 66. All balloons have some form of transition, such
as first transition 72, and the reference zone 66 is to be
distinguished from what is simply a transition, such as transition
72. Thus, the reference zone 66 is provided with a visibly
discernable generally cylindrical exterior configuration in the
inflated state, or other characteristic inflated configuration, so
that it can be distinguished visibly from the transition 72 in
vivo. Thus, the proximal reference zone 66 can be either a
cylindrical section which transitions sharply into a generally
conical transition section, such as first transition 72.
Alternatively, the reference zone 66 may comprise a continuation of
a first transition 72, but with a visibly different angle with
respect to the longitudinal axis of the catheter when compared to
the angle of the surface of the first transition 72 taken in the
axial direction. In one embodiment of the invention, the surface of
the first transition 72 measured in the axial direction lies at an
angle of approximately 20 degrees with respect to the longitudinal
axis of the catheter shaft 74.
[0109] A second transition 76 is provided to step the diameter of
the inflated balloon from that of the proximal reference zone 66 to
the focal zone 68. A third transition 78 is provided to step the
outside diameter of the inflated balloon from the diameter of focal
zone 68 down to the diameter of distal reference zone 70. The angle
of each of the second and third transition sections can vary
depending upon desired performance and design characteristics, but
in one embodiment of the invention have a surface which lies on a
plane extending in the axial direction at an angle of about
11.degree. from the longitudinal axis of the catheter shaft 74. The
axial length of each of the second transition 76 and third
transition 78 will vary depending upon the difference in diameter
of the focal zone from the reference zone, but will generally be
within the range of from about 0.5 mm to about 4 mm.
[0110] A fourth transition 80 is provided to step the diameter of
the balloon 64 from that of the distal reference zone 70 back down
to the diameter of the distal catheter shaft or tip 82.
[0111] The three zone embodiment illustrated in FIG. 7 can be
produced having any of a variety of dimensions, depending upon the
particular contemplated end use of the catheter. In the following
nonlimiting examples of balloon dimensions, the dimensions for the
balloon are recited at 8 atmospheres inflation pressure in an
unrestrained (in vitro) expansion.
[0112] For example, balloons can be readily provided having a focal
zone 68 inflatable to an initial inflation diameter of anywhere
within the range from about 1.5 mm to about 10 mm. For coronary
vascular applications, the focal zone will normally be inflatable
to a diameter within the range from about 1.5 mm to about 4 mm,
with balloons available at every 0.25 mm increment in between.
[0113] The reference zone, such as proximal reference zone 66
and/or distal reference zone 70 is preferably inflatable to a
diameter within the range from about 1.25 mm to about 9.5 mm. For
coronary vascular applications, the reference zone is preferably
inflatable to a diameter within the range of from about 1.25 mm to
about 3.5 mm.
[0114] The focal zone is normally inflatable to a generally
cylindrical profile, which has a diameter that is greater than the
diameter in the reference zone. Neither the focal zone nor the
reference zone or zones need to be precisely cylindrical. Thus, the
present invention can still be accomplished with some slight
curvature or bowing of the surface of the focal zone or reference
zone taken along the axial direction.
[0115] In general, the maximum diameter of the focal zone will be
within the range of from about 7% to about 30% percent or more
greater than the average diameter of the reference zone.
Preferably, the maximum diameter in the focal zone will be at least
about 10% greater than the average diameter in the reference
zone.
[0116] The configuration of the reference zone compared to the
focal zone can be varied considerably, as long as the reference
zone and the focal zone outer diameters can be visualized by the
clinician using conventional fluoroscopic or other visualization
techniques. Thus, although the reference zone can take on a
slightly conical configuration such that it ramps radially
outwardly in the direction of the focal zone, it should not be to
such an extent that the clinician cannot visually differentiate the
inflation profile of the focal zone compared to the reference zone
in vivo.
[0117] The function of the reference zone, to provide a visual
reference to indicate the relative inflation of the focal zone, can
be accomplished by the provision of radio opaque markers at either
end of or within the balloon. For example, inflatable or flexible
radio opaque markers may be provided along the transition in a
balloon from the catheter shaft to the working zone in an
appropriate position along the ramp such that, when the balloon is
inflated, the radio opaque marker provides a visual indication of a
predetermined diameter. Alternatively, the use of radiopaque
inflation media to inflate the balloon can also permit in vivo
visualization.
[0118] Although the preferred embodiments described above rely upon
the balloon to provide a visual reference, the objectives of the
present invention may be accomplished using other visual indica
which will permit the clinician to assess the relative in vivo
inflation of the focal zone. Thus, in a broad sense, the invention
contemplates a visualizable aspect associated with the focal
section and a visualizable reference indica such as the balloon, a
radiopaque marker on or associated with the balloon, radiopaque
inflation media, or others, which allows the clinician to compare
the diameter of the focal section relative to some other visual
reference.
[0119] In addition to the provision of a visual reference to allow
the clinician to assess the inflated diameter of the balloon, the
balloon of the present invention provides a way to focalize the
balloon inflation energy at a predetermined position along the
balloon. The axial length of the focal section can be varied
considerably, depending upon the desired axial length along which
inflation energy is to be focalized. For example, the axial length
of the focal section may be anywhere within the range of from about
0.5 cm to about 5.0 cm. For coronary vascular applications, the
axial length of the focal balloon will normally be within the range
of from about 0.5 cm to about 2.0 cm for performing conventional
PTCA. The axial length will normally be within the range of from
about 0.5 cm to about 5 cm for implanting expandable tubular
stents, depending upon the length of the desired stent. Normally,
the axial length of the focal section will be greater than the
axial length of the stent.
[0120] A variety of focal balloon catheters of the present
invention are preferably available to the clinician having an array
of different axial focal lengths, so that a balloon having the
appropriate focal length can be selected at the time of the
procedure based upon the nature of the procedure to be performed,
and the location in the vasculature. For example, in a curved
portion of the artery, the clinician may wish to minimize the axial
length of the focal zone to the extent possible while still having
a sufficient axial length to accomplish the dilatation or stent
implantation procedure. An excessive axial length in the inflated
balloon for a given curved vessel can elevate the risk of vascular
dissection as is well known in the art.
[0121] The axial length of the reference zone can also be varied
considerably, depending upon the desired performance
characteristics. In general, it has been found that axial lengths
of at least about 3 mm allow ready visualization by the clinician.
Axial lengths much shorter than 3.0 mm may require too much effort
to observe under fluoroscopic conditions, and the reference
function of the reference zone may thus not be readily
accomplished.
[0122] In one embodiment of the invention, produced in accordance
with the three-zone illustration of FIG. 7, the proximal and distal
reference zones each have an axial length of about 5.0 mm and an
inflated diameter of about 3.0 mm at 8 ATM. The axial length of the
focal zone, including the length of the second transition 76 and
third transition 78, is about 8 mm. The diameter of the focal zone
at 8 atmospheres inflation pressure is about 3.5 mm.
[0123] The fixed focal balloon 64 can be manufactured using any of
a variety of techniques which will be understood to those of skill
in the art. For example, the balloon can be manufactured by blowing
suitable tubing stock into a stepped mold cavity. Alternatively,
the tubing stock can be blown into a first mold having a diameter
approximately equivalent to the reference diameter. The balloon can
then be blown into a second mold having a larger diameter section
corresponding to the focal section in the finished balloon. The
balloon is inflated into the larger mold under the application of
heat, as will be understood by those of skill in the art.
[0124] The fixed focal balloon 64 of the present invention or other
fixed focal balloons as described herein can be utilized in any of
the methods described in connection with the differential
compliance balloons of the present invention. Thus, the real-time
diagnostic information about the lesion which is obtainable through
the use of the focal or differential compliance balloons described
in connection with FIGS. 1-6 herein can also generally be achieved
using the embodiment of FIG. 7. Unless clearly specified to the
contrary, the various methods of the present invention, including
both the differential compliance and stent implantation and sizing
methods, are intended to be accomplished by either the fixed focal
balloon or the variable focal balloon embodiments of the methods of
the present invention.
[0125] FIG. 8-18 illustrate a variety of specialized focal and/or
compliant zone balloons in accordance with the present invention.
These balloons can incorporate any of the structures, features, and
methods of the previous embodiments as may be desirable for
particular intended applications. Therefore, construction
techniques, materials, dimensions, capabilities and methodology
discussed above applies to the following embodiments, but will
generally not be repeated below.
[0126] An alternate multi-zone balloon design of the present
invention is schematically illustrated in FIGS. 8 and 9. Referring
to FIG. 8, there is disclosed a catheter having an elongate
flexible tubular shaft 84 such as has been discussed in connection
with previous embodiments. The catheter shaft 84 is provided with a
guidewire lumen 85 and at least one inflation lumen 86. Guidewire
lumen 85 terminates in a distal opening 87 at the distal end 88 of
the catheter.
[0127] A distal region on the catheter is provided with a balloon
assembly 89. The balloon assembly 89 comprises an inner inflatable
balloon 90 disposed within an outer inflatable balloon 91.
Inflation lumen 86 provides fluid communication between a proximal
source of inflation media (not shown) and the interior of the inner
balloon 90. The construction materials, construction techniques and
dimensions of the various components of the various balloons and
catheters illustrated in FIGS. 8 through 18 can be the same or
similar to as those disclosed in connection with previous
embodiments. For example, the inner balloon 90 may be constructed
from a relatively noncompliant material such as PET or a relatively
compliant material such as polyethylene.
[0128] The balloon assembly 89 is configured to produce a three
zone balloon of the type that has been previously discussed, such
that the balloon assembly 89 is inflatable first to a generally
cylindrical configuration as illustrated in FIG. 8 and, thereafter,
to a stepped configuration such as that illustrated in FIG. 9.
Thus, a focal zone 92 (also referred to herein as a compliant zone)
is disposed adjacent one or more reference zones, such as proximal
reference zone 93 and distal reference zone 94.
[0129] In this embodiment, the inner balloon 90 and outer balloon
91 are designed to substantially maintain contact with each other,
except in the region of the focal section 92 once that section has
focalized. Inner balloon 90 and outer balloon 91 may be maintained
in contact at their proximal and distal ends such as by the use of
thermal bonding, adhesives, or other techniques described elsewhere
herein. In addition, expansion limiting bands as have been
previously discussed may also be incorporated into the balloons
illustrated in FIGS. 8 and 9, such as in the reference zones 93 and
94.
[0130] One feature which distinguishes the balloon illustrated in
FIGS. 8 and 9 from those previously discussed is the provision of
one or more apertures 95 for providing communication between the
interior 96 of balloon 90 and the interior 97 of outer balloon 91.
Apertures 95 permit a rate controlled diffusion of inflation media
from the interior 96 of balloon 90 into the space 97 to provide a
delayed, gradual focalization of the focal section 92. In use, the
foregoing features permit the clinician to inflate the balloon
assembly 89 to a preselected pressure, which will cause the balloon
assembly 89 to inflate to its generally cylindrical inflation
profile. Migration of inflation media through the ports 95 then
cause the compliant section 92 to gradually inflate to the second,
stepped configuration of the balloon assembly as illustrated in
FIG. 9.
[0131] Preferably, a plurality of discrete ports 95 is provided in
the balloon 90 to enable the diffusion of inflation media at a
desired rate into the focal section 92. The ports 95 are preferably
each within the range of from about 50 microns to about 400 microns
across, and more preferably are within the range of from about 100
to about 300. In one embodiment, the ports are about 250 microns in
diameter. Depending upon the desired rate of focalization, there
are preferably anywhere from about 5 to about 50 inflation ports 95
on the inner balloon 90. Alternatively, a different number of ports
and/or port diameters can be used depending upon the desired
inflation characteristics of the balloon as a function of time. The
number and size of the inflation ports 95 thus can be optimized for
a particular desired inflation characteristic, taking into account
the viscosity of the inflation media at the temperature the media
is likely to be during an anticipated procedure.
[0132] In one embodiment, the outer balloon 91 comprises a
relatively noncompliant material, which is preformed into the
second, stepped configuration. In this embodiment, a relatively
high pressure can be introduced into inner balloon 90. Inflation
media will diffuse through ports 95 into the focal zone 92, thereby
causing the balloon to assume its second, stepped configuration
substantially without actual expansion of the material of the focal
section 92. Alternatively, at least the focal zone 92 of the outer
balloon 91 and preferably the entire balloon 91 comprises a
relatively compliant material as has been discussed, so that the
focal zone 92 grows by stretching in response to pressure as
inflation media diffuses across inflation ports 95.
[0133] Referring to FIG. 10, there is illustrated a schematic outer
profile of a distally tapered balloon 100 which may be utilized in
connection with any of the embodiments disclosed elsewhere herein.
In general, the outer profile comprises a focal zone 98, which may
or may not be compliant. The focal zone 98 is adjacent at least one
reference zone 99. In this embodiment, the reference zone 99 is
disposed proximally of the focal zone 98. A distal section 101 is
provided on the balloon distally of the focal section 98. Distal
section 101 in the illustrated embodiment comprises an elongate
tapered section which reduces in cross-sectional area in the distal
direction. As an alternate embodiment, distal section 101 may
comprise a generally cylindrical configuration, having a
cross-sectional area in its inflated configuration which is smaller
than the cross-sectional area of the proximal reference zone
99.
[0134] The above described modification to the exterior profile
illustrated in FIG. 10 would thus produce a balloon having a
configuration similar to that illustrated in FIG. 3. However, the
distal cylindrical section or reference zone has a diameter which
is less than the proximal cylindrical reference zone. In general,
the inflated diameter of the distal reference zone will be no more
than about 95% of the diameter of the proximal reference zone.
Preferably, the inflated diameter of the distal reference zone will
be no more than about 80% of the inflated diameter of the proximal
reference zone. In one embodiment, the inflated diameter of the
distal reference zone is about 3.0, the inflated focalized diameter
of the focal section is about 3.5 and the inflated diameter of the
proximal reference zone is about 3.25, at about 12 atmospheres.
[0135] Both of the foregoing modified distal segment configurations
take into account the anatomical environment encountered during
certain dilatations. For example, the native lumen in an artery on
the catheter's distal side of the lesion is often smaller in
diameter than the native lumen on the catheter's proximal side of
the lesion. Provision of a distal section 101 having a step
reduction or a tapered reduction in the inflated diameter can
permit the catheter to accomplish all of the desired functions,
while at the same time reducing the risk of dissection of the
artery. In addition, the tapered distal section such as the
embodiment illustrated in FIG. 8 may facilitate treatment of
lesions or implantation of stents in or adjacent a curved segment
of the artery, as will be apparent to those of skill in the art in
view of the disclosure herein.
[0136] Referring to FIG. 11, there is disclosed a schematic
illustration of a two inflation lumen catheter for use with certain
embodiments of the balloons of the present invention. The catheter
102 comprises an inflatable balloon assembly 103 at its distal end
as has been discussed. The catheter 102 is further provided with a
manifold 104 having a guidewire access port 105 in an over the wire
embodiment. As has been discussed, rapid exchange embodiments may
also be constructed in which the proximal guidewire access port 105
is located along the length of the catheter shaft 102, such as in
the area of about 20 or 25 centimeters proximally of the distal end
of the catheter. In either embodiment, the distal end of the
guidewire lumen typically exits the catheter at a distal port
106.
[0137] The manifold 104 in this embodiment is provided with a first
inflation port 107 and a second inflation port 108 for
communicating with a first inflation lumen 109 and a second
inflation lumen 110, respectively.
[0138] Referring to FIG. 12, the first inflation lumen 109 is in
fluid communication with the interior 112 of an inner balloon 114.
The second inflation lumen 110 is in fluid communication with the
potential space between the inner balloon 114 and an outer balloon
116. As has been previously discussed, inflation of the inner
balloon 114 will in most embodiments cause the inner balloon 114 to
assume a generally cylindrical inflated configuration. Inflation
thereafter of the second balloon 116 will cause the second balloon
116 to assume a focalized configuration such as that illustrated in
FIG. 13.
[0139] In an embodiment in which the outer balloon 116 is made from
a relatively noncompliant material and preformed to have its
stepped configuration, the outer balloon 116 need not necessarily
be secured to the inner balloon 114. Thus, a small space may exist
in the inflated configuration as illustrated in FIG. 13 between the
outer balloon 116 and the inner balloon 114 in the proximal and
distal segments. Alternatively, as has been discussed, the inner
and outer balloons may be secured together in the proximal and
distal zones, depending upon the desired balloon construction
materials and performance characteristics.
[0140] In an embodiment where the inner balloon 114 and outer
balloon 116 are secured together, a flow passage way 118 from the
inflation lumen 110 to the focal section 120 can be readily
provided such as by insertion of a mandril through the inflation
lumen 110 and in between the balloons 114 and 116 prior to the
method step of securing the balloon together. Proximal withdrawal
of the mandril (not illustrated) will thereafter produce a flow
passage way 118 as will be appreciated by those of skill in the
art.
[0141] A variation of the embodiment of FIG. 13 is illustrated in
FIG. 14. In this embodiment, a plurality of delivery ports 122 are
illustrated in the focal section 120 of the outer balloon 116.
Delivery ports 122 will facilitate the site specific delivery of
substances to the vessel wall, such as drugs, or other diagnostic
or therapeutic media as may be desired. This embodiment of the
present invention may be constructed and utilized in a variety of
manners similar to those disclosed in U.S. Pat. No. 5,421,826 to
Crocker, et al., the disclosure of which is incorporated herein by
reference.
[0142] As has been referenced, supra, a multizone balloon including
the technology of the present invention may desirably include a
proximal and a distal focal or compliant section, and a central
reduced diameter section. Two embodiments of the present invention
incorporating this feature are illustrated in FIGS. 15 and 16.
[0143] Referring to FIG. 15, there is disclosed a dual-lobed
balloon catheter 130, comprising a single balloon 138 having a
proximal lobe 140 and a distal lobe 142. By "single balloon" it is
meant that the two or more lobes of the balloon may be inflated by
way of a single inflation lumen. The actual balloon may comprise a
single layer or a plurality of layers, depending upon the desired
construction technique. For example, either one or each of the
proximal lobe 140 and distal lobe 142 may have two or more layers,
expansion limiting bands, or other structures as disclosed
elsewhere herein. A central zone of reduced inflated diameter 144
is disposed between the proximal zone 140 and distal zone 142.
[0144] The balloon 138 is preferably mounted on an elongate
flexible catheter shaft 132. Catheter shaft 132 is preferably
provided with a guidewire lumen 134 and at least one additional
lumen 136 such as for inflation of the balloon 138. Each of the
proximal and distal lobes 140 and 142 may have any of the
dimensions discussed in accordance with previous embodiments. In
addition, either or both of the proximal and distal lobes 140 and
142 may comprise a compliant construction or a substantially
noncompliant construction as has been discussed.
[0145] For example, balloon construction techniques disclosed
previously herein can be utilized to produce a dual-lobed balloon
138 in which the proximal lobe 140 and distal lobe 140 inflate to a
diameter of, e.g., about 2.5 millimeters at six atmospheres. As
inflation pressure is increased to, for example, 14 atmospheres,
either or both of the proximal and distal lobes may be restrained
from expanding beyond about 2.6 or 2.7 millimeters. Alternatively,
the proximal or the distal lobe 140 or 142 or both may expand to as
much as about 3.3 millimeters or more at 14 atmospheres.
[0146] Selection of which of the proximal lobe 140 and distal lobe
142 to be expandable to a greater inflated diameter will depend
upon the intended use of the catheter. For example, in most
coronary vascular applications, the artery descends in diameter in
the catheter distal direction. Thus, it may be desirable for the
proximal lobe 140 to be inflatable to a larger final diameter.
Alternatively, applications of the balloon catheter 130 for such
things as drug or other media infusion, heart valve replacement or
repair, or other uses will require different dimensional
relationships between the proximal lobe 140 and distal lobe 142 as
will be apparent to those of skill in the art in view of the
disclosure herein.
[0147] The central zone 144 can have an inflated diameter anywhere
within the range of from about the outside diameter of the catheter
shaft to about 2.8 mm in a catheter for coronary vascular
applications having a proximal balloon 140 with an inflated
diameter of about three millimeters. The diameter of central
section 144 may be constrained such as through the use of expansion
limiting bands as has been discussed, or through the use of
cross-linking techniques also discussed above. Alternatively, the
central section 144 may be adhered to the catheter shaft 132,
leaving only one or more axially extending flow paths for placing
the interior of lobe 140 in fluid communication with the interior
of lobe 142.
[0148] Referring to FIG. 16, the dual balloon counterpart to the
design illustrated in FIG. 15 is disclosed. In general, dual
balloon catheter 148 comprises a proximal balloon 150, a distal
balloon 152 and a central zone 154 separating the proximal and
distal balloons. The balloons are mounted on an elongate flexible
catheter shaft 156. Catheter shaft 156 is provided with a guidewire
lumen 158, together with at least a first and second inflation
lumen 160 and 162. In the illustrated embodiment, inflation lumen
160 is in communication with proximal balloon 150 and inflation
lumen 162 is in communication with distal balloon 152. In other
respects, the discussion in connection with the dual-lobed balloon
of FIG. 15 is applicable to the dual balloon embodiment of FIG. 16.
In general, the dual balloon embodiment permits slightly more
flexibility in terms of procedure, to the extent that it permits
inflation of either the proximal or the distal balloon first,
followed by inflation of the second balloon where clinically
desirable.
[0149] Referring to FIGS. 17 and 18, there is disclosed a
therapeutic or diagnostic agent delivery embodiment of the
catheters illustrated in FIGS. 15 and 16. Referring to FIG. 17,
there is illustrated a dual-lobed delivery balloon catheter 170.
The catheter 170 comprises a dual-lobed balloon having a proximal
lobe 172, a distal lobe 174 and a central neck portion 176. An
outer perforated or permeable layer 178 extends at least from
proximal lobe 172 to distal lobe 174 to entrap a space 180. Space
180 is preferably annular, and is in communication with an infusion
lumen 182 by way of one or more flow pathways 184. In one
embodiment, outer layer 178 comprises an elongate tubular sleeve,
which is necked down at the proximal end of proximal lobe 172 and
also at the distal end of distal lobe 174.
[0150] The diameter of neck portion 176 is preferably at least
somewhat smaller than the diameter of proximal lobe 172 and distal
lobe 174, to create space 180 for the accumulation of delivery
media. A neck portion 176 which is inflatable to at least about 90%
and preferably 95% or more of the diameter of adjacent lobes 172,
174 permits delivery of media through the delivery zone yet
minimizes the entrapped volume within space 180. The inflated
diameter of neck 176 can be limited by any of the inflation
limiting techniques discussed above, such as one or more inflation
limiting bands (not illustrated), cross linking, materials choice,
wall thickness variations, and the like.
[0151] The inflated diameter of neck region 176 may alternatively
be as small as permitted in view of the wall thickness of the
balloon material, the wall thickness and diameter of the central
guidewire lumen 184, plus the space attributable to at least one
flow passage 186 for communicating between the proximal lobe 172
and distal lobe 174 of the balloon.
[0152] Outer layer 178 may comprise any of a variety of materials,
such as compliant or noncompliant materials well known in the drug
delivery and balloon dilatation arts. For example, layer 178 may
comprise PET, polyethylene, or other membrane materials well known
in the art. Layer 178 may be a permeable membrane, such that
medication or other media diffuses therethrough. Alternatively,
layer 178 is preferably provided with a plurality of perforations
188 for permitting media to escape from the annular chamber 180 to
the surrounding area.
[0153] The diameter and distribution of the perforations 188 can be
modified depending upon the objective of the catheter, such as will
be understood by those of skill in the art in view of the
disclosure herein. For example, provision of delivery perforations
within the range of from about 100 microns to about 300 microns in
diameter will permit a slow weeping expression of fluid media at
low delivery pressures. Alternatively, reducing the cross-sectional
area of the perforations and/or increasing the delivery pressure
can permit the media to penetrate through the elastic lamina layer
and into the arterial wall. Port 188 diameter and distribution
characteristics should also be selected taking into account the
viscosity of any media to be delivered, and/or particle size if a
particulate media is to be delivered.
[0154] One advantage of the configuration illustrated in FIGS. 17
and 18 is the ability to isolate an arterial delivery zone
in-between proximal lobe 172 and distal lobe 174. Inflation of the
dual lobes within an artery can be accomplished at relatively low
pressures to place the balloons in contact with the arterial wall.
Infusion of media into annular chamber 180 for expression through
ports 188 may then be accomplished. Inflation pressure on the
balloon can be increased, if an undesirably large quantity of media
escapes downstream.
[0155] FIG. 18 is in all respects similar to FIG. 17 except for the
use of two separately inflatable balloons. The details and
operation of FIG. 18 will be apparent to those of skill in the art
in view of the discussions in connection with FIGS. 15-17.
[0156] Either of the drug delivery designs of FIGS. 17 and 18 may
also incorporate a perfusion conduit, for permitting perfusion past
the inflated balloon during a drug delivery period. Perfusion
conduits such as those disclosed in U.S. Pat. No. 5,344,402 to
Crocker, the disclosure of which is incorporated herein by
reference, can be utilized.
[0157] Any of the hourglass type balloons of FIGS. 15-18 are
particularly well suited for the implantation and/or sizing of
vascular grafts. For example, an elongate tubular vascular graft
can be positioned on the distal end of the catheter of FIG. 15 and
transluminally advanced to the treatment site. As will be
understood in the art, the treatment site may be a portion of a
vessel having an aneurysm or other wall defect which is desirably
spanned by the graft. The graft is preferably expanded by the
balloon to a first diameter at the treatment site. The proximal and
distal end zones of the graft are preferably expanded to a larger
diameter so that they are seated against the vessel wall proximally
and distally of the vessel wall defect. The balloon may then be
deflated and withdrawn. If the embodiment of FIG. 17 or 18 is used,
the method may additionally include the step of expressing
medication or other media at the treatment site. The balloons of
the present invention may also be utilized for methods of sizing an
already implanted graft and/or infusing medication or other media
at the site of a previously implanted graft by positioning the
balloon within the implanted graft and repeating the steps
described above.
[0158] The present invention may be embodied in other specific
forms without departing from its spirit or essential
characteristics. The described embodiments are to be considered in
all respects only as illustrative and not restrictive. The scope of
the invention is, therefore, indicated by the appended claims
rather than the foregoing description. All changes which come
within the meaning and range of equivalency of the claims are to be
embraced within their scope.
* * * * *