Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to angioplasty catheters for use
in the treatment of stenosed blood vessels. The invention also
relates to a method of manufacturing the catheter.
Angioplasty catheters have been successfully used for a
number of years in the treatment of blood vessels obstructed or
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stenosed with plaque. An angioplasty catheter includes, near
~- its distal end, a balloon which can be inflated by meanis of
pressurized fluid supplied through a lumen in the catheter. The
treatment involves the location of the balloon in the stenosed
section of the blood vessel, followed by inflation and
. deflation. During inflation, the balloon compresses the plaque
and stretches the blood vessel such that the cross-sectional
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`~ area of the stenosis is increased until it is comparable to that
of the unobstructed blood vessel. When the treatment has been
- 15 completed the balloon is deflated and the catheter removed The
treated blood vessel maintains substantially its enlarged
~` cross-section to permit the free flow of blood through this
portion.
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To perform satisfactorily a suitable angioplasty
;~ 20 catheter must possess a number of properties. For ease of
insertion it is preferable that the catheter is flexible, has a
~ relatively small cross-sectional area, and has a smooth outer
!,~'"'' surface. Also~ the method of insertion of the catheter has a
~ significant bearing on the form of the catheter. If the
; 25 catheter is intended for insertion using the Seldinger technique
~ it should have a tapered end and a lumen to receive the
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Seldinger guide wire. Such a catheter ends at an aperture in
. the tapered end
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substantially coaxially with thel ~i9n ~ody of the batheter.
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However, perhaps the most important part of the catheter is theballoon which must be strong enough to withstand the application
of high pressures without rupture and which must always inflate
to a predetermined shape and size.
With reference to the size of the catheter, it is
desirable to minimize the cross-section of the body while
, meeting the requirements of strength, stiffness, resistance to
kinking, torsional rigidity, and surface smoothness needed to
enter and feed the long catheter through the veins or arteries
from an access point remote from the stenosis. This conflicts
with another requirement which is the need to make connections
j to the body at the proximal end and to attach the bulb
'~ satisfactorily near the distal end.
It is known to reduce the diameter of tubing and to
reorientate the molecular structure, and an example of a
specification teaching such a process is GB Patent Application
2 145 064 A.
~; It has been found that these conflicting design
~ 20 requirements can be met in the present novel design in which the
;~ body is formed initially from a dual lumen extrusion of a
-~` diameter which is as small as is practical for making the
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proximal end attachments, and which is then drawn through a die
~,- to reduce the diameter and at the same time enhance the surface
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v 25 finish and molecular orientation of the body. The result is a
catheter having a main body of minimized crossed-section with
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;~ good strength, torque, stiffness and resistance to kinking
characteristics.
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; The invention wil be better understood with reference
to the drawings, in which:
. Fig. 1 is a perspective view of an angioplasty catheter
,: in accordance with a preferred embodiment of the present
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invention;
Fig. 2 is an enlarged isometric view of a balloon
forming part of the catheter;
Fig. 3 is a sectional view on line 3-3 of Fig. l;
Fig. 4 is a sectional view on line 4-~ of Fig. l;
Fig. 5 is a diagrammatic sectional view illustrating
the drawing of the main body to reduce cross-section and to
change the physical characteristics of the main body of the
catheter;
Fig. 6 is a sectional view illustrating the method of
manufacturing a tip on the catheter;
Fig. 7 is a diagrammatic sectional view illustrating a
method of manufacturing the balloon;
Figs. 8 to 11 are views, mostly in section,
illustrating the method of manufacturing the junction at the
proximal end where tubes provide access for a Seldinger wire and
for providing a supply of fluid to inflate the balloon; and
Fig. 12 is a side view of the resulting structure.
Before describing the catheter of the present invention
~; 20 in detail, a brief description of the use and features of an
angi~plasty catheter will be provided.
An angioplasty catheter is typically elongate and
tubular~ and is provided with a balloon near or at its distal
end and radiopaque bands defining the extremities of the
balloon. The catheter is inserted at a convenient location and
fed into the stenosed blood vessel until the balloon is located
in the narrowed portion of the blood vessel. Fluid from an
external supply is then used to inflate the balloon such that it
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; compresses the obstructing plaque and stretches the plaque
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coated walls of the blood vessel. When the physician is
satisfied that the blood vessel has been widened sufficiently,
the balloon is deflated and the catheter removed.
The preferred embodiment of the angioplasty catheter
according to the present invention will now be described in
detail, firstly with reference to Fig. 1 of the drawings. This
view shows in perspective an angioplasty catheter, designated
generally by the numeral 20, including a flexible main body 22
having a distal end 24 defining a tapered tip 25 to facilitate
insertion into a vein of a patient, and a proximal end 26 for
connection, by means of connection piece 28, to the respective
distal ends oE a guide wire tube 30 and a fluid supply tube 32.
The tubes 30, 32 are in communication with respective circular
guide wire and fluid supply lumens 34, 36 defined within the
main body 22 (Fig. 3) and are provided with luer fittings 35, 37
at the respective proximal ends. Different coloured marking
sleeves 38, 3g help distinguish the tubes from one another
~although in practice the fluid supply lumen 36 is of
si~nificantly smaller cross-section than lumen 34)
The body 22 extends from the connection piece 28 to the
` tip 24 and passes through a balloon 40, details of which are
provided below. A tubular shipping protector (not shown) for
y location over the distal end 24 and balloon 40 would normally be
provided to protect the balloon and to retain it in a collapsed
condition ready for insertion.
Reference is now made to Fig. 2 of the drawings which
shows the distal end of the catheter in greater detail with the
balloon in a collapsed condition. The balloon 40, located at
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the distal end 24, is formed of a Nylon membrane which is
~lexible and substantially inextensible (i.e. not elastomeric)
and, when inflated, is in the form of a cylinder having tapering
ends (as indicated in ghost outline3. The distal and proximal
ends 46, 48 of the membrane locate snugly over the distal end 24
of the main body 22 with the distal end 46 being mated to the
body just short of the tapered tip 25. An side opening or
aperture 50 in the wall of the main body 22 provides fluid
communication between the smaller fluid supply lumen 36 and the
interior o~ the balloon 40 between ~he body 22 and the membrane
of the balloon.
A pair of radiopaque bands 54, 55 are attached around
the body 22 inside the balloon 40 and near the ends 46, 48 for
~ monitoring the position of the balloon.
15 To inflate the balloon 40, fluid is supplied under
!,' pressure through the fluid supply tube 32 and the fluid supply
;~;i lumen 36, and then through the aperture 50 into the balloon 40.
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~; Thus, the balloon is pushed radially outwardly by the fluid
pressure to assume the shape shown by the chain-dotted lines in
; 20 Fig. 2, so that the balloon 40 has a diameter greater than that
of the main body 22. On deflation, and on withdrawing the fluid
by suction (i.e~ negative pressure) the balloon ~olds and
collapses to lie close to the outer surface of the body, as
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shown in Figs. 2 and 4.
t, 25 Reference is next made to Fig. 5 which illustrates
;~ diagrammatically how the main body 22 is drawn down. As seen in
Fig. 1, tbe main body meets, adjacent the connection piece 28, a
short portion 56 of larger diameter than the main body 22. ~his
corresponds to the diameter at portion 58 in Fig. 5 and a
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1 329090
diameter 60 corresponds to that of the main bodyO The purpose
of this reduction in diameter will be explained in more detail
later but for the moment it is sufficient to understand how it
is accomplished. A length of extruded Nylon having a
cross-section similar to that shown in Fig. 3, but of the
diameter of portion 58, is first cut to remove some material to
; leave a leading end piece 62. This piece is small enough to
pass readily through an opening 64 in a heated die 66. A pair
of supporting rods 68, 70 are engaged in the respective lumens
s,
10 34, 36 (Fig. 3) and have proportions corresponding to the
required sizes of these lumens as drawn in Fig. 3. Of course
s the rods will be loose in the original extrusion because it is
of larger size than the body 22.
The die 66 includes a conical lead-in portion 72 which
blends smoothly into the polished opening 64, and at the outlet,
a rounded nose portion 74 is provided so that after extrusion,
the body can be drawn backwards through the die to remove it.
j~ After cutting the extrusion tc provide the end piece
62, the rods 68, 70 are engaged and the end piece 62 fed through
the heated die to be used to draw the remaining extrusion
through the die. This drawing process takes place to
effectively orientate molecular structure, improve the surface
finish, and enhance the density of the Nylon to give it better
torsional stiffness and strength. This continues in the manner
illustrated in Fig. 5 until the portion 56 (Fig. 1) is reached,
$ at which point the drawing is discontinued and the body is
`.~ withdrawn in the opposite direction from the die 66. An end
`~ part, including the leading end piece 62, is cut off the
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extrusion leaving only the required part of the body. The
length of the catheter can be fixed at this stage.
The next step in the process is to form the tip 25
(Fig. l~ and the method of doing this is illustrated
diagrammatically in Fig. 6. Here a heated die 76 has an
internal shape corresponding to that of the required tip and an
~; opening 78 aligned with the tip to receive an end part of the
mandrel 80 which is engaged through the guide wire tube of the
body. A rod or mandrel 82 is provided in the fluid supply tube
and, under the influence of heat from the die 76, the body is
advanced into the die and deformed into the shape shown in Fig.
6. It will be seen in this Fig. that the fluid supply tube has
^, been terminated at its end whereas the guide wire tube has been
,~ retained in an open condition to provide access for the
~ 15 Seldinger wire during insertion. The form of the structure is
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such that the end iS conical so that the Seldinger wire is
centered relative to the catheter during insertion.
As a separate procedure, a membrane -is formed to be
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used to make the balloon. This procedure is iLlustrated
2Q diagrammatically in Fig. 7. A tube of Nylon having a wall
diameter thickness of about 0.015 inches is located in a copper
mould 84 made up of two halves 86, 88. The tube 56 is cut at a
~ lower end 90 and a clamp 92 is attached to a short end piece 94
J`'~ which extends from the mould 84 to seal the end of the tube and
to ensure that the tube is not pulled from the mould. The tube
and mould are then suspended in a heated oil bath 96 at about
`3' 170 to 175C for three minutes. The total weight of the mould
and accessories is about 150gm. and this weight tends to stretch
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the heated tube such that the molecular orientation becomes
axial along the length of the tube.
After three minutes in the oil bath 96 a pressure of
400 p.s.i. is applied to the inside of the tube from an external
supply (not shown) causing it deform to occupy the interior of
the mould, oil in the mould being pushed from the mould through
relief holes 98. After a short interval of time the pressure is
released and the mould containing the resulting membrane 100 is
removed from the oil bath and placed in freon which acts as a
coolant and disperses the oil. The membrane retains the tapered
.~ cylindrical shape of the mould, the deformed portion having a
wall thickness in the order of 0.00025 to 0.0005 inches.
; Reference is next made to Fig. 8 which is the first of
~r a series o~ Figs. 8 to 12 demonstrating the manufacture of the
15connection piece 28 shown in Fig. 1. The portion 56 of the main
body is held in place to receive, under the influence of some
heat, a pair of mandrels 102, 104. These mandrels have leading
ends corresponding to the sizes of the respective guide wire
tube 30 and fluid supply tube 32, and leading end portions 106,
108 are conical with the axis inclined as indicated by the chain
dotted center lines to meet cylindrical portions 110, 112 of the
mandrels. This arrangement is necessary since they are to be
used to form an end of the main body and deformation can only
take place outwardly. The mandrels are entered into the lumens
2534, 36 to the position shown generally in Fig. 9 where it will
be seen that the ends of the lumens have been flared. Next, and
` as seen in Fig. 10 diagrammatically, the distal ends of the
A respective guide wire tube 30 and fluid supply tube 32 are
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engaged in the flared ends of the lumens 34, 36 followed by a
pair of suitably proportioned mandrels 114, 116 which are
engaged through the tubes and into the body portion 56. The
tubes and body are of Nylon which is a thermoplastic material so
that deformation of these parts can be achieved to bring them
together in a single assembly.
As seen in Fig. 11, a thin sleeve 118, of a Nylon
'1 material is engaged over the body portion 56 and extending
outwardly beyond this portion terminating around the tubes 30,
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32~ Over this is applied a heavy sleeve 120 of silicon rubber
which is stretched into place. The assembly is then heated and
compressed in a suitable clamping arrangement such as a pair of
formed die halves (not shown) to bring the materials into
,;~ flowing engagement with the mandrels and to seal the Nylon parts
to one another. The silicon rubber sleeve 120 helps to
distribute the load and to apply a circumferential compressive
loading on the parts to cause flowing around the mandrels.
The resulting structure looks generally like that shown
in Fig. 12. The tubes 30~ 32 are supported where they meet the
2Q connection piece and the internal surfaces are smooth since they
were formed around the mandrels 114, 116 which of course are
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~;~ withdrawn after the procedure is completed.
The procedure described with reference to Figs. 8 to 12
can be varied by using different sleeve arrangements and even by
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,~25 building up several sleeves one over another to provide more
material flowing and to enhance the strength of the structure.
-The resulting catheter 20 (Fig. 1) has retained the
necessary sizing to perform the asembly shown in Figs. 8 to 12
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while at the same time resulting in a main body of r
diameter thereby meeting the conflicting desirable design
criteria for manufacturing angioplasty catheters. The resulting
body is not only smaller in diameter but is a more constant
diameter and is enhanced due to the molecular orientation
resulting from drawing and the enhanced surface finish provided
t by the polished die through which the body was drawn. The small
diameter catheter has substantially the same strength
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characteristics both in torsion and flexibility achieved by the
general extrusion so that it is not of any diminished capability
?~; but on the contrary, has improved characteristics desired by
practioners in using these devices.
In the preferred embodiment the main body has an
outside diameter of 5 French (about 0.0065 inches) which is
drawn about 5.5 French with guide wire lumen about 0.037 inches
and fluid supply lumen about 0.017 inches, The portion 56
(which corresponds to the original extrusion) is 7 French (about
~ 0.090 inches), and the lumens 0.039 and 0.024 inches in diameter.
~ This embodiment and others are within the scope of the
invention as defined and claimed.
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