U.S. patent number 4,820,349 [Application Number 07/088,098] was granted by the patent office on 1989-04-11 for dilatation catheter with collapsible outer diameter.
This patent grant is currently assigned to C. R. Bard, Inc.. Invention is credited to Mark A. Saab.
United States Patent |
4,820,349 |
Saab |
April 11, 1989 |
Dilatation catheter with collapsible outer diameter
Abstract
A balloon dilatation catheter having a balloon at its distal end
includes a distal segment having a collapsible outer diameter. The
distal segment includes an inner shaft and a generally coaxial
outer surrounding sleeve formed from a very flexible, thin wall,
high-strength polymeric material. The balloon is formed integrally
with the sleeve and is collapsible about the shaft together with
the sleeve. The distal segment of the catheter exhibits a high
degree of trackability over a guidewire through tortuous blood
vessels. When in its collapsed configuration, the distal segment of
the catheter defines a reduced profile which is less obstructive to
blood flow through the blood vessel containing the catheter distal
segment, such as a coronary artery. In a modified embodiment of the
invention, the flexible thin wall sleeve extends over a greater
length of the catheter and may extend to the full length of the
catheter. In the modified embodiment, when the sleeve is collapsed
about the inner shaft a reduced profile is defined along the length
of the catheter. When contained within a guide catheter, the
dilatation catheter provides for an enlarged cross-sectional flow
area within the guide catheter, thus enhancing proximal dye
injections and pressure measurements or, alternately, enabling the
use of a smaller diameter guide catheter.
Inventors: |
Saab; Mark A. (Lawrence,
MA) |
Assignee: |
C. R. Bard, Inc. (Murray Hill,
NJ)
|
Family
ID: |
22209361 |
Appl.
No.: |
07/088,098 |
Filed: |
August 21, 1987 |
Current U.S.
Class: |
606/194; 604/913;
604/96.01 |
Current CPC
Class: |
A61M
25/1029 (20130101); A61M 25/1036 (20130101); A61M
25/104 (20130101); A61M 25/1038 (20130101); A61M
2025/1081 (20130101) |
Current International
Class: |
A61M
29/02 (20060101); A61M 25/00 (20060101); A61M
029/02 () |
Field of
Search: |
;128/344
;604/101,53,96 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
"USCI Gruntzig Dilaca Lo Profile II Bal&oon Dilatation
Catheters", No. 1-86/5090043, 1986..
|
Primary Examiner: Cross; E. Rollins
Attorney, Agent or Firm: Wolf, Greenfield & Sacks
Claims
Having thus described the invention, it is desired to claim and
secure by Letters Patent:
1. A dilatation catheter comprising:
an elongated flexible shaft having a proximal segment and a distal
segment, the distal segment of the shaft being smaller in diameter
than the proximal segment of the shaft;
the proximal segment having an inflation lumen extending
therethrough;
a sleeve extending over the distal segment of the shaft, the
proximal end of the sleeve being attached to the shaft and being in
communication with the inflation lumen;
the distal end of the sleeve being attached to the distal end of
the shaft;
the sleeve having an integral enlarged diameter balloon portion,
both the balloon and the sleeve being formed from a thin walled,
flexible material and being inflatable and deflatable, both the
sleeve and balloon being collapsible about the shaft in response to
a negative pressure applied to the inflation lumen,
whereby the diameter of the catheter in the region of the sleeve
may be made to conform closely to the smaller reduced diameter of
the distal segment of the shaft.
2. A dilatation catheter as defined in claim 1 wherein said balloon
has a wall thickness to outer diameter ratio of less than about
5.0.times.10.sup.-3.
3. A dilatation catheter as defined in claim 1 wherein the wall
thickness of the sleeve is substantially less than the wall
thickness of the shaft.
4. A dilatation catheter as defined in claim 1 wherein the sleeve
and the balloon are formed from a single unitary piece of polymeric
material.
5. A dilatation catheter as defined in any of claims 1 to 4 wherein
the proximal segment extends over most of the length of the
dilatation catheter and the distal segment extending over a
relatively short portion of the overall length of the catheter.
6. A dilatation catheter as defined in claim 5 wherein the distal
segment is between about 10 to 15 centimeters in length.
7. A dilatation catheter as defined in claim 5 further comprising a
main lumen extending through the shaft and being open at the distal
end of the shaft, and means at the proximal end of the catheter for
communicating with the main lumen.
8. A dilatation catheter as defined in any of claims 1 to 4 wherein
the proximal segment extends over a relatively short portion of the
catheter and the distal segment extends over a relatively long
portion of the catheter.
9. In combination, a dilatation catheter as defined in claim 8 and
a guide catheter, the dilatation catheter being receivable within
the guide catheter, whereby when the dilatation catheter is
deflated, the combination defines a fluid flow area greater in
cross-section than that defined between the proximal shaft portion
of the dilatation catheter and the internal lumen of the guide
catheter.
10. A dilatation catheter as defined in any of claims 1 to 4, the
catheter being dimensioned to be insertable into the coronary
arteries to enable the catheter to be used in performance of
angioplasty of the coronary arteries.
11. A method for performing angioplasty in an artery
comprising,
providing a catheter having a proximal segment and a distal
segment, the distal segment including a thin walled, flexible
sleeve having an integral enlarged diameter balloon portion formed
integrally therewith,
said sleeve and balloon being inflatable and deflatable being
collapsible to a smaller diameter when collapsed;
inserting at least the distal segment of the catheter into the
blood vessel while maintaining the catheter in said collapsed
configuration; and
thereafter inflating the balloon portion.
12. A method of defining claim 11 further comprising;
said catheter being provided with a main lumen adapted to receive a
guidewire;
said catheter having a guidewire extending through its main lumen
when the catheter is inserted into the artery;
manipulating the guidewire and the catheter in the artery to
position the balloon within the artery;
said manipulation being effected while maintaining the sleeve and
balloon in a collapsed configuration.
13. A dilatation catheter as defined in claim 5, the catheter being
dimensioned to be insertable into the coronary arteries to enable
the catheter to be used in performance of angioplasty of the
coronary arteries.
14. A dilatation catheter as defined in claim 6, the catheter being
dimensioned to be insertable into the coronary arteries to enable
the catheter to be used in performance of angioplasty of the
coronary arteries.
15. A dilatation catheter as defined in claim 7, the catheter being
dimensioned to be insertable into the coronary arteries to enable
the catheter to be used in performance of angioplasty of the
coronary arteries.
16. A dilatation catheter as defined in claim 8, the catheter being
dimensioned to be insertable into the coronary arteries to enable
the catheter to be used in performance of angioplasty of the
coronary arteries.
17. A dilatation catheter as defined in claim 9, the catheter being
dimensioned to be insertable into the coronary arteries to enable
the catheter to be used in performance of angioplasty of the
coronary arteries.
18. A dilatation catheter comprising:
an elongate flexible supporting shaft having an inflation lumen
extending therethrough;
an elongate sleeve extending over the supporting shaft, the sleeve
having an integral enlarged diameter balloon portion at its distal
region, both the balloon and the sleeve being formed from a thin
walled flexible material and being inflatable and deflatable, both
the sleeve and the balloon being collapsible about the supporting
shaft in response to a negative pressure applied to the inflation
lumen.
19. A dilatation catheter as defined in any of claims 1 to 4, 15 or
18 wherein the wall thickness of the sleeve and the balloon is no
greater than about 0.0005" thick.
Description
FIELD OF THE INVENTION
The invention relates to improvements in balloon dilatation
catheters such as those used in angioplasty procedures and,
particularly percutaneous transluminal coronary angioplasty.
BACKGROUND OF THE INVENTION
In recent years there has been a substantial increase in the use of
percutaneous transluminal angioplasty for the treatment of vascular
stenoses and, particularly, stenoses of the coronary arteries. The
use of balloon dilatation catheters for such angioplasty procedures
may provide for many patients an effective alternative to coronary
artery bypass surgery.
In a typical coronary angioplasty procedure, a guide catheter is
introduced into the patient's arterial system through the femoral
artery and is advanced through the aorta and to the ostium of the
coronary artery. Once the guide catheter is positioned with its tip
intubated in the coronary ostium, a balloon dilatation catheter
which typically will have been fitted with a small diameter
guidewire, such as the steerable guidewire disclosed in U.S. Pat.
No. 4,453,930, is advanced through the guide catheter to and into
the coronary artery. Once the dilatation catheter and steerable
guidewire are located in the coronary arterial tree, the catheter
is positioned by manipulations of the catheter and the guidewire in
which the distal tip of the guidewire is selectively steered
through the branches and tortuous passages of the arterial anatomy
and with dilatation catheter being advanced over the guidewire
after the guidewire is positioned. When the balloon is positioned
in the stenosis, it is inflated under pressure to effect the
dilatation, thereby, forcably enlarging the narrowed lumen of the
artery.
Among the desirable features of the dilatation catheter is that it
should be highly flexible so that it can track easily along the
guidewire through sharp bends and tortuous coronary arteries. If
the catheter is too stiff, it will not track well and instead of
following the natural contour of the artery and flexible guidewire,
it will tend to straighten the artery which causes it to press
against the arterial walls as well as the guidewire which, in turn,
presents difficulty in manipulating and positioning the guidewire
and catheter. Another difficulty encountered with balloon
dilatation catheters is that the presence of the catheter in the
artery presents an obstruction to blood flow in the artery. Where
the angioplasty procedure is performed in arteries that are already
suffering from narrowing stenoses, the presence of the catheter
during the angioplasty procedure itself presents an obstruction and
somewhat of an increased risk of ischemia in distal portions of the
artery. It is among the general objects of the invention to provide
an improved dilatation catheter that displays superior trackability
and also minimizes the degree of obstruction within the artery.
The angioplasty procedure typically includes the periodic injection
of radiopaque dyes into the coronary arterial tree to enable the
physician to observe, fluoroscopically, the conditions of the
coronary anatomy during the procedure as well as to visualize the
anatomy to help in positioning the dilatation catheter. It also is
among the common procedures to make measurements of the blood
pressure both proximally and distally of the stenosis to compare
the pressure gradient in the artery before the dilatation with the
pressure gradient after dilatation. Ideally, the dilatation
procedure enlarges the arterial obstruction thereby reducing the
pressure gradient along that region. The observation of a reduced
pressure gradient signifies that the dilatation procedure is
accomplishing its objective and is an important feature to be
monitored by the physician. Typically, the guide catheter, the tip
of which is in communication with the cornary ostium, is used to
inject dye into the coronary arterial tree as well as to make
pressure measurements on the proximal side of the stenosis. In
order to obtain enhanced dye injections and pressure measurements,
it is desirable that the cross-sectional flow area through the
guide catheter be as large as possible. However, it also is
desirable to maintain a reduced diameter for the guide catheter so
that it will be more easily inserted into the patient and so that
the distal end of the guide catheter may be more securely intubated
into the coronary ostium. It is among the general objects of the
invention to provide a modified dilatation cathether which achieves
these objectives.
Thus, it is among the general objects of the invention to provide a
novel dilatation catheter construction which displays superior
tracking and a low profile for the balloon as well as for the
distal segment of the catheter and which provides other significant
advantages over prior diliation catheters.
SUMMARY OF THE INVENTION
The catheter includes a flexible shaft having proximal and distal
segments. A main lumen and an inflation lumen extend through the
shaft. The distal segment of the shaft is of reduced diameter. The
inflation lumen terminates at the juncture of the proximal and
distal segments of the shaft. The distal segment of the shaft is
surrounded by a sleeve formed from a very thin, flexible and strong
polymeric material such as highly oriented polyethylene
terephthalate and the dilatation balloon is formed integrally with
the sleeve. The proximal end of the sleeve is attached to the
distal portion of the proximal segment of the shaft so that the
inflation lumen is in communication with the interior of the
sleeve. The distal end of the sleeve is attached to the distal
region of the distal segment of the catheter shaft. Both the sleeve
and the balloon are extremely flexible and both are collapsible
about the shaft in response to application of a negative pressure
to the inflation lumen. The thin flexible wall of each of the
sleeve and balloon enable them to collapse closely against the
smaller diameter of the distal segment of the shaft thereby
providing a reduced profile for the distal segment of the catheter
when the catheter is in the deflated mode. The very thin wall of
the sleeve presents negligible bending resistance and enables the
distal segment of the catheter to have an extremely high degree of
flexibility and superior ability to track over a guidewire even in
sharply curved or tortuous blood vessels. Additionally, the low
profile of the distal segment of the catheter when the sleeve is
collapsed provides for reduced obstruction and increased
cross-sectional flow area within the coronary artery in which the
catheter is placed.
In the foregoing embodiment of the invention, the distal segment
extends over a length of the order about ten to fifteen
centimeters, a distance sufficient to reach the distal extremities
of the coronary arterial tree without extending any portion of the
proximal region of the catheter shaft out of the guide catheter. In
a modified embodiment of the invention, the collapsible sleeve
extends over a greater distance along the catheter and may extend
fully to the proximal end of the catheter. In the modified
embodiment, the outer diameter of the catheter thus is collapsible
substantially to the smaller diameter of the shaft to provide an
increased annular flow area between the dilatation catheter and the
guide catheter. The increased flow area inables improved dye
injection capability through the guide catheter while the
dilatation catheter is in place and also provides for improved
pressure measurement through the guide catheter, proximally of the
balloon. Alternately, the modified embodiment of the dilatation
catheter enables the use of a guide catheter having a smaller
diameter without reducing the annular flow area through the guide
catheter. The use of a smaller guide catheter has advantages in
that it is more easily placed and positioned in the patient and
reduces the size of the entry site which decreases bleeding and
reduces recovery time after the procedure.
It is among the general objects of the invention to provide an
improved balloon dilatation catheter.
Another object of the invention is to provide a dilatation catheter
having superior tracking ability.
A further object of the invention is to provide a dilatation
catheter which has a sufficient stiffness in its proximal segment
so that it may be easily pushed over a guidewire yet which displays
a high degree of flexibility in its distal segment for superior
tracking.
A further object of the invention is to provide a dilatation
catheter that provides less obstruction to the artery when in a
deflated mode.
Another object of the invention is to provide a dilatation catheter
which enables use of a smaller diameter guide catheter.
A further object of the invention is to provide a dilatation
catheter that enables improved proximal dye injection and pressure
measurement to be made through a guide catheter, through which the
dilatation catheter extends.
Another object of the invention is to provide a dilatation catheter
having an inner shaft portion and an outer tubular sleeve
surrounding the inner shaft portion and in which the outer tubular
portion is collapsible about the inner shaft in response to
negative pressure applied to the sleeve.
Another object of the invention is to provide an improved catheter
adapted for use in percutaneous translumenal angioplasty of the
coronary arteries.
Another object of the invention is to provide a catheter which
enables the practice of an improved method of angioplasty and,
particularly, angioplasty of the coronary arties.
DESCRIPTION OF THE DRAWINGS
The foregoing and other objects and advantages of the invention
will be appreciated more fully from the following further
description thereof, with reference to the accompanying drawings
wherein:
FIG. 1 is a fragmented illustration of the catheter;
FIG. 2 is an enlarged sectional fragmented section of the distal
region of the catheter;
FIG. 3 is a diagrammatic illustration of the coronary anatomy with
a guide catheter, a dilatation catheter and small diameter
steerable guidewire extending through the anatomy;
FIG. 4 is a diagrammatic illustration of the mold used in making
the integral sleeve and balloon used in the invention;
FIG. 5 is a sectional illustration through the catheter with the
sleeve and balloon in an expanded configuration as seen along the
line 5--5 of FIG. 2;
FIG. 6 is an illustration of the sleeve similar to FIG. 5 with the
sleeve collapsed about the catheter shaft;
FIG. 7 is a sectional illustration of the balloon as seen along the
line 7--7 of FIG. 2 with the balloon in an expanded
configuration;
FIG. 8 is an illustration similar to FIG. 7 but with the balloon in
a collapsed configuration;
FIG. 9 is an elongated fragmented illustration of a modified
embodiment of the invention in which the sleeve extends
substantially the full length of the catheter;
FIG. 10 is a diagrammatic cross-sectional illustration of the
modified embodiment of the catheter within a guide catheter and
depicting the increased cross-sectional flow area within the guide
catheter provided by the invention; and
FIG. 11 is a diagrammatic cross-section illustration of the
modified embodiment of the invention illustrating the manner in
which it may be used with a smaller diameter guide catheter.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The balloon dilatation catheter is indicated generally at 10 in
FIG. 1 and may be considered as having a proximal segment 11 and a
distal segment 13. The catheter includes a shaft 12 which may be
extruded from an appropriate polymer such as polyvinyl chloride or
polyethylene. The shaft 12 includes a main, proximal portion which
may be considered as having a full diameter 14 and a distal shaft
extension 16 of a smaller diameter. The proximal shaft portion 14
has a main lumen 18 formed therethrough which continues through the
distal shaft segment 16, the main lumen 18 terminating at a distal
outlet 20 at the distal tip of the catheter. The proximal shaft
portion 14 also is provided with an inflation lumen 22 having a
smaller cross-sectional area, the inflation lumen 22 terminating at
the region of the transition 15 of the proximal segment 11 to the
distal segment 13. A sleeve 24 formed from a thin, highly flexible,
high-strength polymeric material, as will be described, extends
over the distal segment 13 of the catheter, and encloses the distal
shaft extension 16. The proximal end of the sleeve 24 is adhesively
attached to the proximal shaft portion 14 in the transition region
15 adjacent the distal end of the inflation lumen 22 and is
substantially the same outer diameter as the proximal shaft portion
14. The distal end of the sleeve 24 is formed to define a reduced
diameter neck 26 which is adhesively attached to the distal portion
of the distal shaft extension 16.
A tip marker 27 which may be formed from a band or coil of
radiopaque material preferably is mounted on the distal tip of the
shaft extension 16. An additional radiopaque marker band 29 may be
mounted on the distal shaft extension 16 within the region of the
balloon to indicate the position of the balloon fluoroscopically
during the dilatation procedure. It may be noted that the shaft
extension 16 may be reinforced with an internally embedded helical
coil 31 that extends along the shaft extension 16 to reinforce the
shaft extension 16 and prevent it from collapsing under the
pressures developed during the dilatation procedure. The coil 31
may be embedded in the shaft extension 16 by forming shaft
extension from a pair of tubes of plastic (such as
polyvinylchloride) with the coil 31 placed between the tubes. The
tubes then may be fused together with the coil 31 being embedded in
the material. The balloon marker 29 also may be attached in the
same manner.
The distal region of the sleeve 24 is formed to define an enlarged
diameter dilatation balloon 28. The dilatation balloon 28 may be
inflated and deflated by applying positive or negative fluid
pressure through inflation lumen 22 and the generally annular
continuation of the inflation lumen 22. As will be described in
further detail, both the balloon 28 and the proximal portion of the
sleeve 24 are collapsible about the smaller diameter distal shaft
extension 16 when negative pressure is applied to the inflation
lumen 22.
As shown in FIG. 1, the catheter shaft 12 is provided, at its
proximal end, with a bifurcated fitting 30 from which a pair of
tubular legs extend, including a main lumen leg 32 which
communicates with the main lumen 18 of the catheter and an
inflation lumen leg 34 which communicates with the inflation lumen
22 of the catheter. Each of the legs 32, 34 is provided with a luer
connector 36, 38 respectively for connection to various adaptors,
syringes, inflation devices and the like.
FIG. 3 illustrates, diagrammatically, the manner in which a
dilatation catheter is used with a guide catheter 40 and a small
diameter steerable guidewire 52 to place the dilatation catheter 10
in a selected branch of the coronary arterial tree. FIG. 3
illustrates the guide catheter 40 as having been placed so as to
extend through the aorta 42 and aortic arch 44 and downwardly
through the ascending aorta 46 with the distal tip 48 of the guide
catheter 40 intubated in the selected coronary ostium 50 at the
base of the coronary arterial tree. With the guide catheter 40 so
positioned a dilatation catheter 10, having a guidewire 52 in its
main lumen 18 with its distal tip protruding distally beyond the
distal tip of the catheter 10, is dvanced through the guide
catheter 40 and beyond the distal tip 48 into the coronary artery.
The physician may inject radiopaque dye through the guide catheter
40 into the coronary arteries to visual them on a fluoroscope and
also may measure the patient's blood pressure proximally of the
balloon 28. The physician also may inject radiopaque dye from the
distal end of the dilatation catheter 10 and also may make distal
pressure measurements through the main lumen 18 of the dilatation
catheter 10. In accordance with the present invention, the distal
segment 13 and sleeve 24 of the dilatation catheter are
sufficiently long so that even when the distal end of the
dilatation catheter is extended as far as possible into the
coronary arterial tree, the transition region 15 remains inside of
the guide catheter 40.
In accordance with the invention, the sleeve 24 and balloon 28 are
formed to be very thin and highly flexible yet sufficiently strong
to withstand the pressures developed during dilatation without
excessive compliance. In the preferred embodiment of the invention,
the sleeve 24 and balloon 28 are formed in a single integral piece
from polyethylene terephthalate (PET). By way of example the sleeve
24, including the balloon 28, may be between 10 to 15 centimeters
long. For a balloon diameter of the order of 3 millimeters, and a
burst pressure of about 15 atmospheres, the balloon 28 may have a
wall thickness of the order of 0.0002 inches and a length of about
20 millimeters. The portion of the sleeve 24 proximally of the
balloon 28 may have a diameter in the order of 0.053 inches, a wall
thickness of 0.0005 inches and a length of about ten to thirteen
centimeters.
The integral balloon and sleeve may be formed using methods
described in copending application Ser. No. 001,759 filed Jan. 9,
1987 entitled Thin Wall High Strength Balloon and Method of
Manufacture which describes the use of high-stretch ratios and heat
setting to provide balloons having surprisingly thin, flexible and
strong properties. Balloons made in accordance with the techniques
described in that application are characterized by a wall thickness
to diameter ratio of less than 5.0.times.10.sup.-3. Typically, such
balloons may have a radial tensile strength greater than about
35,000 psi. For example, in order to form the illustrative integral
balloon and sleeve described above a mold, as illustrated in FIG. 4
may be used. The mold as shown in FIG. 4 includes a mold body 70
having an internal bore which defines the intended dimension of the
finished balloon and sleeve. The mold also includes a pair of end
members including a fixed end member 74 and a movable end member
72. Both end members include outwardly tapering portions 74A, 72A
respectively, which merge into smaller diameter end bores 74B, 72B
respectively. A water jacket 76 having inlet and outlet ports 78,
80 surrounds the mold 70. The mold parts are formed from a material
such as brass having good heat conductivity.
The mold 70 receives a tubular parison indicated in phantom at 82
in FIG. 4. The parison is gripped at its ends which extend
outwardly of the mold, one of the ends of being sealed and the
other end being connected securely to a source of fluid (such as
gas) under pressure as by a fitting 84. The clamp 85 and fitting 84
are mounted, by means not shown, to enable them to be drawn upon
axially so as to impart an axial stretch to the parison 82.
The parison is formed from a polymer such as PET and its dimensions
are selected with respect to the intended final configuration of
the balloon to result in the balloon having the desired properties
and dimensions, as described more fully in application Ser. No.
001,759, reference being made to said application for full details
of the procedure.
It should be noted that the parison is thin walled and after
stretching is highly oriented, being stretched radially close to
the elastic limit of the material at the inner surface of the tube.
Orientation takes place at an elevated temperature that is
controlled by a heat transfer of fluids circulated through the
water jacket. The parison is drawn axially and then, while being so
drawn is expanded radially within the mold. The orientation takes
place at a temperature between the first and second order
transition temperatures of the material, preferably at about
90.degree. C. for the PET material. For the 3.0 millimeter diameter
balloon of the illustrative embodiment, the starting parison may be
a tube of PET having inner diameter of 0.429 millimeters and an
outer diameter of 0.638 millimeters. The parison may be stretched
axially to about 3.1 times its original length. During the axial
stretching the parison is expanded radially by admitting gas under
pressure into the tubular parison through fitting 84 to stretch the
parison to the enlarged diameters as determined by the mold
members. After the parison has been radially enlarged to the
diameters of the mold the balloon pressure is released and the
longitudinal stretching at both ends of the parison is continued.
Then the short end of the parison (contained in the movable mold
member 72) is held stationary and the long end of the parison (held
within fixed mold member 74) is continually drawn to continue to
stretch the long portion of the parison that will become the
elongate proximal portion of the sleeve 24 of the present
invention. After the axial stretching has been completed the
stretched and expanded balloon and sleeve is repressurized and is
then subjected to a heat setting step in which steam is circulated
through the jacket 76 at a temperature above the stretching
temperature and is maintained for a time sufficiently to increase
the degree of crystalinity in the material. After the heat setting
step the mold is cooled to a temperature less than the second order
transition temperature of the material and the balloon and integral
sleeve may be removed from the mold. Preferably, the illustrative
embodiment of the invention is made using an internal diameter
stretch ratio of 7 and an outer diameter stretch ratio of about 4.7
for the balloon. Preferably the portion of the sleeve proximal of
the balloon has an ID stretch ratio of about 3.1 and an OD stretch
ratio of about 2.1.
The catheter having the foregoing construction displays a sleeve 24
that is extremely flexible, thin walled and very strong. The sleeve
presents minimal resistance to bending which results in a highly
flexible distal segment 13 of the catheter. The degree of
flexibility is such that the entire sleeve is easily collapsible
about the distal shaft extension 16.
FIGS. 5 and 6 illustrate, respectively, the expanded and collapsed
configurations of the proximal portion of the sleeve 24 and FIGS. 7
and 8 similarly illustrate the expanded and collapsed
configurations of the balloon portion 28. As shown in FIG. 6 the
sleeve 24 is collapsed closely about the distal shaft extension 16
and defines a diameter that is effectively the same as that of the
distal shaft extension 16. When collapsed the sleeve 24 forms one
or two wings 54 which do not present any significant obstruction to
blood flow when the device is in an artery. Thus, when the distal
segment 13 of the catheter is disposed within the coronary arterial
tree and while the catheter is maintained in its collapsed
configuration, the obstruction to blood flow through the coronary
artery containing the catheter is reduced and blood perfusion is
enhanced. FIG. 8 illustrates the configuration of the collapsed
balloon 28. Because the balloon is larger in diameter, it usually
will tend to form a pair of very thin wings 55 that may tend to
fold over each other, as illustrated.
FIG. 9 illustrates a modified embodiment of the invention which
differs in that the sleeve 24' extends over the full length, or
nearly the full length, of the catheter. In this embodiment, the
full diameter shaft 12' may be relatively short and may make a
transition to a smaller diameter single lumen shaft near the
proximal end of the catheter. In this embodiment, the sleeve 24' is
joined at transition region 15' to the full diameter shaft and
extends over a length that is coextensive with a substantial length
of the guide catheter 40 with which the dilatation catheter is to
be used. Thus, the distal segment 13' of this embodiment is
substantially longer than in the embodiments of FIG. 1.
FIG. 10 illustrates, diagrammatically, how the modified form of the
invention provides for increased cross-sectional flow area through
the guide catheter. The figure illustrates, in solid, the
cross-sectional flow area through the generally annular region
between the guide catheter 40 and the dilatation catheter 10' (in
solid). The circle indicated in phantom at 56 illustrates the
normal outer diameter of a conventional non-collapsible dilatation
catheter. The increased flow area achieved with the present
invention is represented by the cross-hatched area 58.
FIG. 11 illustrates the manner in which the invention may be
employed to use a smaller diameter guide catheter 40'. In those
cases where it is adequate to maintain approximately the
conventional cross-sectional flow area between the guide catheter
40' and dilatation catheter, the collapsibility of the dilatation
catheter enables the required cross-sectional flow area to be
achieved within the confines of a smaller diameter guide catheter
40'. The use of a smaller diameter guide catheter provides a number
of advantages in that it can be inserted percutaneously into the
patient through a smaller opening in the patient's blood vessel and
it also is more easily and more securely intubated into the
coronary ostium.
Thus, from the foregoing it will be appreciated that the invention
provides an improved catheter construction having superior
flexibility and trackability. Additionally, the collapsibility of
the outer diameter of the catheter provides for improved blood
perfusion through the coronary arteries. Moreover, the invention
may be incorporated in a catheter so as to provide increased
cross-sectional flow area when used with a conventional guide
catheter or, alternatively, enables the use of a smaller diameter
guide catheter.
It should be understood, however, that the foregoing description of
the invention is intended merely to be illustrative thereof and
that other modifications and embodiments may be apparent to those
skilled in the art without departing from its spirit.
* * * * *