Angioplasty catheter with spiral balloon

The invention provides a balloon of non-elastomeric material which is spirally wrapped onto the main body of the catheter. The catheter is inserted in this condition and on inflation, the balloon aligns itself with the axis of the main body causing the body within the balloon to twist and store energy which is available for collapsing the balloon after use.

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. 
BACKGROUND OF THE INVENTION 
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 
compresses the obstructing plaque and stretches the plaque 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. 
Angioplasty catheters have been successfully used for a number of years in 
the treatment of blood vessels obstructed or stenosed with plaque. An 
angioplasty catheter includes, near its distal end, a balloon which can be 
inflated by means 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 area of the stenosis is 
increased until it is comparable to that of the unobstructed blood vessel. 
When the treatment has been 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. 
To perform satisfactorily a suitable angioplasty 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. The catheter which is 
the subject of the present invention is intended for insertion using the 
Seldinger technique and therefore preferably has a tapered end and a lumen 
to receive the Seldinger guide wire. The catheter ends at an aperture in 
the tapered end substantially coaxially with the main body of the 
catheter. However, perhaps the most important part of the catheter is the 
balloon 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. 
Also, during insertion and removal, the balloon must present a small 
profile as it is moved longitudinally. 
It has long been accepted that in order to reduce the balloon profile 
during insertion, the balloon must be wrapped in some way about the body. 
An example of a typical structure intended for this purpose is found in 
U.S. Pat. No. 4,338,942 to Fogarty. The balloon is attached to an internal 
rod which has an exposed control knob at the proximal end of the catheter. 
On turning the knob, the balloon is rotated at the distal end to impart a 
twist which wraps the balloon on the main body. There is no energy stored 
other than possibly in the balloon. After insertion, the twist is removed 
to allow inflation and then, to permit removal, the twist is again 
applied. This structure is rather complex and requires a long rod through 
the length of the device. Further, this structure is not suitable for 
insertion using the Seldinger technique. 
Another exemplary structure which uses a mechanical wrapping device is 
shown in U.S. Pat. No. 4,646,719 to Neuman et al. A tube runs the length 
of the device to permit Seldinger insertion through the tube and this tube 
can be rotated to wrap the balloon against the resistance of a spring. 
After insertion, the spring energy can return the balloon to its normal 
position for inflation. During insertion the balloon must be kept in the 
wrapped condition against the urging of the spring which will tend to 
unwrap the balloon. 
A different approach is taught in U.S. Pat. No. 4,402,307 to Hanson et al. 
A balloon is provided which is attached at its distal end to a tubular 
central member which extends along the length of the catheter. A tool is 
provided for engaging the distal end to rotate that end and wrap the 
balloon around the tube as energy is stored in the twisted tube. Provided 
that sufficient vacuum is applied, the balloon will remain in this 
condition during insertion. Should there be any difficulty with the vacuum 
then of course the balloon will unwrap itself under the influence of the 
tube returning to its normal condition. After insertion, the balloon is 
released and can not be wrapped again in the same fashion in which it was 
wrapped in the first place. However access is provided to the tube at the 
proximal end for rotating the tube which will presumably wrap the balloon 
in the fashion taught by Fogarty. 
All of the prior art structures suffer from serious disadvantages and among 
them are complexity, dangerous situations arising should vacuum fail 
during insertion, and such difficulties as unwrapping the balloon 
accurately to ensure that it is in the proper position for inflation after 
it is located in the patient. 
It is an object of the present invention to provide an improved angioplasty 
catheter which overcomes some of the disadvantages of the prior art. 
SUMMARY OF THE INVENTION 
The invention provides a balloon of non-elastomeric material which is 
spirally wrapped onto the main body of the catheter. The catheter is 
inserted in this condition and on inflation, the balloon aligns itself 
with the axis of the main body causing the body within the balloon to 
twist and store energy which is available for collapsing the balloon after 
use.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
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 or tip 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 
of 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 
colored marking sleeves 38, 39 help distinguish the tubes from one another 
(although in practice the fluid supply lumen 36 is of significantly 
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 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 the distal end 24, is formed of a 
Nylon membrane which is flexible and substantially inextensible (i.e. not 
elastomeric) and, when inflated, is in the form of a cylinder having 
tapering ends (as indicated in ghost outline). 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. A 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 of the balloon 40 between the 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. 
To inflate the balloon 40, fluid is supplied under pressure through the 
fluid supply tube 32 and the fluid supply lumen 36, and then through the 
aperture 50 into the balloon 40. Thus, the balloon is pushed radially 
outwardly by the fluid pressure to assume the shape shown by the 
chain-dotted lines in 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 folds and 
collapses to lie close to the outer surface of the body, as shown in FIGS. 
2 and 4. 
Reference is next made to FIG. 5 which illustrates diagrammatically how the 
main body 22 is drawn down. As seen in FIG. 1, the main body meets, 
adjacent the connection piece 28, a short portion 56 of larger diameter 
than the main body 22. This corresponds to the diameter at portion 58 in 
FIG. 5 and a diameter 60 corresponds to that of the main body. 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 34, 36 (FIG. 
3) and have proportions corresponding to the required sizes of these 
lumens as drawn in FIG. 3. Of course 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. 
After cutting the extrusion to 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 
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. 1) 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 Seldinger wire 
during insertion. The form of the structure is 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 used to make the 
balloon. This procedure is illustrated 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 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 170.degree. to 175.degree. C. 
for three minutes. The total weight of the mould and accessories is about 
150 gm. and this weight tends to stretch 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 a series of FIGS. 8 
to 12 demonstrating the manufacture of the connection 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 34, 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 respective 
guide wire tube 30 and fluid supply tube 32 are 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 material is engaged over 
the body portion 56 and extending outwardly beyond this portion 
terminating around the tubes 30, 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 connection piece and the 
internal surfaces are smooth since they were formed around the mandrels 
114, 116 which of course are 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 building up several 
sleeves one over another to provide more material flowing and to enhance 
the strength of the structure. 
Turning now to the balloon, after manufacture as described the reference to 
FIG. 7, the ends are trimmed, and it is positioned on the main body and 
secured in place using a suitable adhesive. If preferred, the balloon can 
be bonded to the main body. 
FIG. 13 illustrates diagrammatically the balloon in position on the main 
body 22. For simplicity the wrinkles that will inevitably appear in the 
balloon are omitted and an imaginary line 130 is drawn on the balloon in a 
spiral to indicate that the balloon has been attached in this fashion. In 
other words, the proximal end of the balloon 48 was attached to the main 
body 22, the balloon twisted about the axis of the body 22 and then the 
distal end 46 attached so that the balloon has a spiral twist in it. As 
mentioned previously, there is a molecular orientation which will be along 
lines such as line 130. The balloon therefore will have a tendency on 
inflation to take up its normal shape as manufactured in the process 
described with reference to FIG. 7. Consequently, after inflation the 
balloon will take on the position shown in FIG. 14 where the line 130 has 
become axial. In order to accommodate this, the portion of the main body 
defined between the distal and proximal ends 46, 48 will be subject to a 
torque indicated by the arrow 132 resulting in this portion of the body 
receiving an axial twist thereby storing energy in the body. Upon removing 
the pressure from the balloon 40, the energy stored in the body will 
return the balloon to the FIG. 3 position (or substantially so) thereby 
again storing the balloons snugly about the body 22 for removal. 
It is of course to be appreciated that angioplasty catheters of the type 
described are not reused. The energy stored in the body 22 would 
eventually affect the body if it were used repeatedly but this is not the 
case in this structure. 
In the preferred embodiment the main body has an outside diameter of 5 
French (about 0.065 inches) 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. The ends of the balloon are 
twisted relative to one another by about 360 to 540 degrees. 
This embodiment and others are within the scope of the invention as defined 
and claimed.