U.S. patent number 3,896,815 [Application Number 05/477,167] was granted by the patent office on 1975-07-29 for expansible tip catheters.
This patent grant is currently assigned to Shiley Laboratories, Inc.. Invention is credited to Samuel Burd, Bruce E. Fettel.
United States Patent |
3,896,815 |
Fettel , et al. |
July 29, 1975 |
Expansible tip catheters
Abstract
Expansible tip catheters in which the distal portion of a single
lumen flexible plastic catheter tube is manufactured with a
physical characteristic such that when fluid under pressure is
introduced therein the wall of this distal portion begins to expand
outwardly, and additional fluid pressure causes the wall to expand
both outwardly and also along the longitudinal catheter axis.
Inventors: |
Fettel; Bruce E. (Diamond Bar,
CA), Burd; Samuel (Long Beach, CA) |
Assignee: |
Shiley Laboratories, Inc.
(Santa Ana, CA)
|
Family
ID: |
23894804 |
Appl.
No.: |
05/477,167 |
Filed: |
June 6, 1974 |
Current U.S.
Class: |
606/194; 604/908;
606/192; 606/200 |
Current CPC
Class: |
A61M
25/00 (20130101); A61M 25/0074 (20130101); A61B
17/22032 (20130101); A61M 25/0069 (20130101) |
Current International
Class: |
A61B
17/22 (20060101); A61M 25/00 (20060101); A61M
025/00 () |
Field of
Search: |
;128/2M,245-246,341-344,325,348-351,DIG.9,DIG.16,242,347 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Gaudet; Richard A.
Assistant Examiner: Opitz; Rick
Claims
What is claimed is:
1. In an expansible tip embolectomy catheter of the type which is
so constructed and arranged as to be inserted distal end first into
blood passages in the body which comprise an elongate flexible tube
sealed at the distal end and connected at the proximal end to a
pressurized fluid source connector for supplying fluid under
pressure into said tube during use, the improvement wherein:
said tube has an outside diameter from about 0.026 inches to about
0.092 inches;
an elongate portion of the tube adjacent the distal end is
pre-stretched to be less resistant to lateral expansion than the
remainder of the tube such that upon injection of fluid under
pressure into said tube said elongate distal end portion expands
laterally first, said lateral expansion beginning initially in and
progressing along said elongate distal end portion in preference to
lateral expansion of the remainder of said tube; and
including an elongate flexible wire secured to the connector and
the distal end of the tube, extending through the tube to prevent
extension and to guide the tube during insertion.
2. The improved expansible tip catheter defined in claim 1 wherein
the outside diameter of the unexpanded tube is substantially
uniform along the length thereof.
3. The improved expansible tip catheter defined in claim 1 wherein
the tube is constructed in two sections, an elongate tip portion
composed of a resilient polymer, and the remainder of the tube
which is composed of flexible polymer, the resilient polymer tip
portion being less resistant to lateral expansion than the
remainder of the tube.
Description
FIELD OF THE INVENTION
This invention relates to expansible tip catheters designed to be
advanced through small passageways, a particular class of such
catheters being embolectomy and thrombectomy catheters designed to
remove emboli and thrombi from arterial and venous passageways.
Other catheters of this general type are the occlusion catheter and
dialysis shunt declotting catheters.
BACKGROUND OF THE INVENTION
For several years catheters have been available for surgically
removing emboli and thrombi from the arterial and venous
passageways. Such emboli and thrombi may result from natural causes
such as myocardial infarction and thrombophlebitis and may be also
induced as a result of other surgical techniques such as open heart
surgery, catherization procedures and saphenous vein shunts for
hemodialysis.
The most commonly used prior art catheter comprises a flexible tube
having one or more apertures at its distal end. A balloon is
secured at this distal end with the ends of the balloon sealed to
the catheter on opposite sides of these apertures. A flexible guide
wire may be temporarily positioned through the length of the
catheter in order to provide support for the catheter while it is
being extended through the body passageway. Otherwise, the very
small flexible tube, typically having an O.D. of between 0.026 to
0.092 inches and a wall thickness in the range of 0.004 to 0.016
inches, tends to curl back rather than advancing through the artery
or vein of the patient. After the tube is in place with the prior
art catheter, this guide wire is removed. In use, the surgeon
passes the distal end with the balloon deflated through the
thrombus. A fluid or gas is then passed from the proximal end
through the tube to inflate the balloon. The inflated catheter is
then withdrawn, carrying with it the thrombus.
A disadvantage of this prior art catheter is that substantial care
must be taken while inflating the balloon. A relatively high
inflation pressure is required to inflate the balloon and if the
surgeon is not very careful, the balloon may be overinflated,
resulting in rupture of the balloon and discharge of the fluid or
gas into the bloodstream of the patient. Even if the balloon does
not rupture, such over inflation may sufficiently enlarge the
outside diameter of the balloon so as to damage the wall of the
body passageway.
The prior art catheter described above does not permit the balloon
to be inflated while the insertion wire is in place. As a result,
the catheter is substantially transparent to X-rays and therefore a
radiopaque solution must usually be used to inflate the balloon if
the surgeon wishes to determine the position of the catheter by an
X-ray procedure. Another disadvantage of the prior art
configuration is that if the surgeon wants to reinsert the
guidewire after the catheter has been removed from the patient, the
guidewire must be reinserted down the length of the catheter. This
is a tedious and time consumming operation because of the small
dimensions of the catheter and wire.
SUMMARY OF THE INVENTION
The catheter of the present invention is an improvement in the type
of catheter which is constructed and arranged to be inserted,
distal end first, into body fluid passages, such as arteries,
veins, and the like. These catheters typically comprise an elongate
flexible tube which is sealed at the distal end and is connected at
the proximal end to a connector which, in use, is connected to a
source of pressurized fluid for selectively injecting fluid under
pressure into the tube. The improvement of this invention is that
an elongate portion of the tube adjacent the distal end is made of
a material which, either by its composition or its pre-treatment,
e.g., prestretching, or both, is less resistant to lateral
expansion, outwardly from the center, than is the remainder of the
tube. Thus, upon injection of fluid under pressure into the tube
during use the elongate distal end portion expands laterally first.
This lateral expansion begins initially in the elongate distal end
portion and progresses along said portion as additional fluid is
injected into the tube in preference to the lateral expansion of
the remainder of the tube. Typically, a flexible wire or other
means extends through the length of the tube to prevent extension
of the tube during use and to guide the tube during insertion.
Structurally, the catheter comprises a continuous flexible single
lumen plastic tube which has a guide wire which extends through the
tube and is secured at both the proximal and distal ends of the
tube. The tube is sealed at the distal end and a small portion of
the tube proximate the distal end of the single lumen, which may
typically range from 0.5 to about 1.0 inch in length, differs from
the remainder of the tube in that it has the physical properties or
characteristics of being less resistant to lateral expansion
outwardly away from the center of the lumen. Thus, when fluid under
pressure is passed through the catheter from the proximal end to
the distal end, the fluid causes the walls of this distal end
portion of the plastic tube to expand outwardly. The expansion
begins initially in this distal end portion and progresses along
the distal end portion. The plastic tube which is more resistant to
lateral expansion than the distal end portion does not expand
during this procedure.
In both its non-inflated and inflated conditions, the catheter has
marked differences over the prior art. In its non-inflated state,
the catheter presents a substantially uniform outside diameter
along its length and has the physical characteristics of a uniform
length of small diameter flexible tube. The structural complexity
of the superimposed balloon of the prior art and the difficulties
attendant to the use of the prior art catheters are entirely
obviated by the present invention.
Another important difference, with respect to the prior art
catheters, is that the elongate distal end portion expands
initially outwardly in preference to expansion of the remaining
part of the catheter tube, but this distal end portion also expands
laterally progressively along the longitudinal axis of the catheter
the full length of the distal end portion. This longitudinal
expansion capacity accommodates a considerable amount of excess
fluid. One of the serious risks and disadvantages of the prior art,
the difficulty in providing the proper amount of pressurized fluid
for safe and effective use, has been obviated. Accordingly, if the
surgeon should inadvertently overfill the catheter with fluid, the
additional fluid is accommodated by longitudinal expansion of the
distal end portion without substantial risk of rupturing the walls
of the plastic tube.
The permanently attached guidewire provides several significant
advantages. This wire prevents longitudinal extension of the
catheter tube since both the distal and proximal ends of the tube
are secured to opposite ends of the guidewire. The wire is
radiopaque so that the surgeon may with X-ray technique determine
the precise location of the catheter within the patient without
having to use a radiopaque solution. The wire supports the small
flexible plastic tube while it is being inserted and withdrawn from
the patient. And, since the wire is permanently attached, there is
no lost time caused by having to reinsert the wire through the
catheter tube.
One practical advantage of catheters constructed according to this
invention is that they may be shipped in smaller containers than is
normally possible with catheters which embody an unsupported
plastic tube. Since plastic catheters, if not supported by a
guidewire, will take a permanent set if coiled, these catheters
typically must be packaged and shipped in a flat condition. This
requires long, bulky packages, with increased risk of damage during
shipment. Storage of catheters in large numbers also occupies a
great deal of valuable and limited space. In contrast, the
catheters of this invention can be coiled and shipped in small
boxes, since the guidewire does not take a permanent set and any
set or deformation in the plastic has little if any effect upon the
catheters characteristics during use.
Another feature of this invention is that in the event of over
inflation and rupture of the expansible distal end portion of the
catheter, an occurrence less likely with the present catheter than
those of the prior art, the plastic tubing material remains
integral and coherent. This reduces the possibility of foreign
plastic material being left in the body fluid passageway after the
catheter has been withdrawn.
FIG. 1 is a perspective view of the expansible tip catheter
construction in accordance with the present invention;
FIG. 2 is a cross-sectional view of the preferred embodiment of the
catheter shown in FIG. 1;
FIG. 4a shows the expansible tip catheter inflated to its normal
position; FIG. 4b shows the expansible tip catheter overinflated;
and FIG. 4c shows the expansible tip catheter grossly overinflated;
and
FIGS. 5a through 5f show the various stages of construction of the
expansible tip catheter of FIG. 3.
Referring first to FIG. 1, the basic structural components of the
present invention are described. The expansible tip catheter 10
comprises a continuous flexible single lumen plastic tube 11 having
an expansible tip portion 12 at its distal end and a luer connector
13 or like fluid coupling at its proximal end adapted to be
connected to a syringe 14 or like source of fluid to which exterior
pressure may be applied. After the distal tip has been advanced by
the surgeon through a passageway to the desired location, the
syringe 14 is connected to the coupling 13 and a predetermined
amount of fluid is introduced under pressure into the catheter
lumen. This fluid causes the wall of the distal end of the catheter
to expand outwardly.
A cross-sectional view of one embodiment of the present invention
is shown in FIG. 2. The proximal end 20 of the catheter tube 11 is
permanently joined to the luer connector 13 by means of an inner
bushing 22. At its distal end, the catheter is sealed by lacquer
plug 23 and one or more suture ties 24. Extending completely
through the lumen and permanently secured at the distal and
proximal ends thereof is a flexible guidewire 25 having a pair of
beads 26, 27 permanently secured to the distal end of the wire. As
shown, the wall 28 of the flexible tube proximate those beads is
drawn tightly into the valley between these beads and secured by
one or more of the suture ties 24. At the proximal end, the wire 25
is permanently secured by a loop 29 extending through the stem wall
30 of the luer tip as shown.
The expansible distal end portion of the catheter is formed by
modifying the lateral expansion characteristics of the distal end
portion of the catheter lumen. In the simpliest form of the
invention, the lumen 11 is an extrusion of a stretchable
elastomeric material, for example block copolymers of styrene and
butadiene. At the distal end, at a point 31 closely proximate the
beads 26 and 27 of the wire 25, the tube is physically expanded
along its longitudinal axis a predetermined amount during the
manufacturing process. This pre-stretching or pre-extension
permanently changes the characteristics of that portion of the tube
so treated. When stretched a pre-determined amount and released,
the tube will elastically recover its original unstretched
dimensional configuration, but this portion is less resistant to
lateral expansion than is the unextended material. It is not fully
understood what physical changes occur in elastomer, but it is
believed that the stretching changes the orientation of the
polymeric components. The effect, in any event, is to lower the
modulus of elasticity of the extended portion. Thus, although the
material returns to its original unstretched dimensional
configuration after being extended, it is less resistant to lateral
expansion than it was before being extended. When fluid under
pressure is introduced into the tube the material "remembers" the
point 31 at which it was previously extended and the outward
expansion of the tube begins at this point 31 and progresses
longitudinally along the length of the pre-extended distal end
portion of the tube.
A disadvantage of the simplified embodiment of the invention
described hereinbefore is that the wall of the catheter may, by
virtue of the internal fluid pressure, be induced to expand
outwardly at some place other than its distal tip portion. For
example, if the distal tip is inserted into a passageway that is
too small for proper expansion, as the fluid pressure is increased
such other portion of the catheter wall may be caused to expand
outwardly at such point. Also, in this simplified embodiment,
should any other portion of the catheter be inadvertently stretched
during handling by the surgeon or his assistants, such portion
would be as likely to expand as the distal end.
In the preferred embodiment of this invention shown in the
cross-sectional view of FIG. 3, substantially the entire length of
tubing 35 formed from material which is substantially resistant to
expansion when pressure is applied to its interior wall. An
exemplary material is a block polymer of styrene and butadiene
filled with polypropylene. The distal expansible tip portion 12 is
formed from a short length of tubing 36 having a different plastic
configuration, which is less resistant to lateral expansion, having
one end 37 abutted to and permanently joined to one end 38 of the
substantially longer length of filled, more expansion resistant
material. Advantageously, this distal tube 36 is formed of the
unfilled styrene butadiene elastomer and has inside and outside
diametral dimensions identical with the main catheter tube 35 so
that the catheter is a continuous single lumen of uniform outside
diameter (O.D.) and inside diameter (I.D.). In the manner described
above, the distal end is stretched at a point 31 to impart a
permanent physical characteristic to the unfilled plastic material.
As a result, when fluid pressure is applied through the luer
connector 13 at the proximal end through the first length of tube
35 and hence the second distal tube 36, the exterior wall of the
distal portion is caused to expand outwardly beginning at the point
31 which has been physically stretched. The physical
characteristics of the tube 35 inhibit expansion of any other
portion of the catheter lumen.
The improved inflation characteristics of the invention are
illustrated in FIGS. 4a, 4b and 4c. FIG. 4a illustrates the
inflation of the expansible tip 12 to its normal expanded position,
i.e., the form that it would normally assume during an embolectomy
procedure, for example. As shown, beginning at the point 31, the
point at which the catheter has been stretched, the wall of the
distal tip has been caused to expand outwardly to a predetermined
outside diameter. Only relatively small fluid pressures are
required to reach and maintain this position.
A significant feature of this invention is that should the surgeon
inadvertently overfill the catheter with fluid, such additional
fluid is readily accommodated by the catheter in that the plastic
tip may expand both outwardly in the direction of the arrows 40,
41, but also progressively along the longitudinal axis 42 of the
catheter lumen to assume the configuration shown in FIG. 4b. In the
embodiments of FIGS. 2 and 3, this additional expansion is
accommodated by the portion of the distal tip 12 which either has
not previously been stretched or not stretched to the same degree
as the portion at point 31. As excess fluid is forced into the
distal end, this unstretched or partially stretched portion is
caused to stretch, thereby providing an appreciable expansion
volume beyond the normal expanded state shown in FIG. 4a. As a
result, the catheter of this invention can accommodate a
substantial excess introduction of fluid without rupturing the wall
of the expansible distal tip, even to a grossly distended state
shown in FIG. 4c.
The single lumen construction of the present invention provides
other important advantages as well. Thus, this construction
provides a catheter of having a substantially uniform outside
diameter along its entire length, thereby facilitating the
advancement of the tube through the vascular system or similar
passageway. For a given uninflated O.D., the O.D. of the expansible
tip is relatively large. A ratio of 6.6 for the inflated O.D. to
uninflated O.D. is easily achieved.
The permanently secured guidewire provides a nonremovable support
for the catheter as it is advanced through a passageway.
Accordingly, after the catheter is withdrawn, no time is lost in
having to reinsert the guidewire. Also, the guidewire is
radiopaque, thus relieving the surgeon from having to use a
radiopaque solution when it is desired to locate the catheter
position by X-ray. The wire prevents longitudinal extension of the
catheter as fluid is forced therethrough to expand the distal tip.
Another advantage exhibited by catheters constructed in accordance
with this invention is that in the tests conducted to date, when
the catheter was overfilled to force the expansible tip to rupture,
the tip portion remained in one integral piece. This is of course
desirable since it precludes leaving any foreign matter inside the
body passageway.
The procedures involved in manufacturing the catheter shown in
FIGS. 1-3 are illustrated in FIGS. 5a, 5b, 5c, 5d, 5e, and 5f.
Referring to FIG. 5a, the proximal end of the filled
poly-styrene-butadiene tube 35 is permanently bonded to the inner
and outer bushings 21, 22. A suitable lacquer may serve as the
bonding medium. An inner mandrel 50 is positioned through the
entire length of the tube 35 so as to prevent the entry of any
lacquer into the internal of the lumen. The end 37 of the distal
unfilled poly-styrene-butadiene tube 36 is bonded to end 38 of tube
35 also by a suitable lacquer. The mandrel 50 is then removed. At
this point of time during the manufacturing procedure, no physical
stretching is applied to the distal tube 36.
As shown in FIG. 5b, the next step of the procedure is to insert
the guidewire 25 through the entire length of the catheter lumen
and through the stem wall 30 of the luer tip 13. As shown, the luer
tip is held at an angle with the wire so that the wire pierces the
wall of the stem as shown. The wire is then bent in the form of a
loop as shown in FIG. 5c and the stem of the luer tip is lacquer
bonded to the proximal end of the catheter lumen by means of the
bushings 21, 22 as shown in FIG. 5d. This step permanently secures
one end of the guidewire to the proximal end of the catheter.
Following the attachment of the wire at the proximal end of the
catheter, the distal end of the catheter 10 is compressed so as to
expose the pair of beads 26, 27 located on the wire. (See FIG. 5e)
These beads are then liberally covered with the bonding lacquer and
the catheter allowed to return to the original configuration, shown
in FIG. 5d, thereby providing a lacquer bond between the inside
wall of the distal end and the beads 26, 27 and the lacquer plug
23. One or more knots of suture thread 24 are then tied around the
exterior of the catheter so as to compress the catheter wall 28
into the valley between the wire beads as shown in FIG. 3. The
distal end including these suture ties is then dipped in lacquer to
provide a relatively smooth surface over the distal end of the
catheter 10.
The distal tube 36 is then stretched as shown in FIG. 5f. This may
be manually performed by grasping the portion of the catheter
overlying the bead 27 with the fingers of one hand and grasping the
immediately adjacent catheter wall at point 31 with the fingers of
the other hand and pulling the two apart a predetermined amount S.
A single stretch of the predetermined dimensions is all that is
required to give the material the permanent characteristic of being
less resistant to lateral expansion while allowing the catheter
material to elastically return to its original dimensional
configuration after being released. The catheter is then tested by
introducing air at the proximal end and causing the distal end to
inflate to the desired configuration. After sterilization, the
catheter is ready for surgical application.
By way of specific example only, embolectomy catheters in a range
of O.D.'s may be constructed in accordance with this invention
according to the following specifications; all dimensions being
stated in inches.
__________________________________________________________________________
Guide Length Length Catheter Wire Bead of of Size O.D. I.D. O.D.
Diameter Tube 35 Tube 36 S
__________________________________________________________________________
2F .026 .017 .008 .022 32 .3 1.0 to 1.5 3F .039 .024 .008 .022 32
.3 0.7 to 1.2 4F .052 .028 .015 .030 32 .3 0.4 to 0.9 5F .065 .037
.015 .030 32 .3 0.2 to 0.7 6F .078 .043 .015 .030 32 .3 0.2 to 0.7
7F .092 .060 .015 .030 32 .3 0.2 to 0.7
__________________________________________________________________________
There is no particular criticality of materials, since a number of
polymeric materials exhibit the characteristic of being less
resistant to expansion or stretch once having been stretched than
in the unstretched or unextended condition.
It will be understood that other means of obtaining compatible
materials having differing resistance to expansion can be used
without departing from this invention. For example, it is known
that irradiation of polymers by electrons, X-rays, gamma rays,
etc., effects the degree and nature of polymerization and modifies
the physical characteristics of most polymers. In general,
irradiation tends to cross-link the polymer thus reducing its
thermoplastic and/or elastic characteristics; however, irradiation
under varying conditions with specific polymers can result in other
changes. It is within the scope of this invention to modify part of
the plastic tube either to increase or to decrease the resistance
to expansion, depending upon the polymer system being used, to
obtain the structure defined herein.
In addition, of course, the material must be sufficiently
compatible with body fluids and tissues as to be usable in the
fluid passages in the body without undue irritation or other
complications arising from reaction of the material with body
fluids or tissue. Again, however, a large number of materials have
been found to be sufficiently biologically acceptable for this
purpose. Indeed, most conventional polymers are sufficiently
compatible for temporary use in the body. For example, the
polyolefins, polyethylene and polypropylene, the polyacetals,
poly-butadiene-styrene copolymers, the polyfluoro and
polyfluorochloro-polymers, such as TEFLON and KEL-F and other
polymers and copolymers are generally suitable, when properly
processed and handled, for at least temporary residence in the
body. While biological compatability of the guidewire is not
particularly critical, since it is not normally in contact with
body fluids, it is desirable to provide a material which has at
least temporary compatability with body fluids and tissues. No. 302
stainless steel wire, and other stainless steel products as well as
other alloys are suitable.
The medical literature on prosthetic devices give many examples of
materials which have been found suitable for use in connection with
body fluids and tissues both temporarily and on a long term
basis.
One particularly suitable material is the KRATON polymers which are
described as thermoplastic elastomers produced by Shell Chemical
Co., Polymers Division, for pharmaceutical and medical
applications. These KRATON products are block copolymers of
butadiene and styrene which have rubbery properties but do not
require vulcanization. The butadiene-styrene copolymers may be
blended with fillers, such as polypropylene, to give more expansion
resistant characteristics to the products. These polymers are
fabricated and processed using conventional extrusion and molding
techniques.
The polymers may be bonded by solvent welding or cemented using an
appropriate lacquer. It is often convenient to prepare a lacquer
which is composed of the polymer or polymers to be bonded dissolved
in an appropriate solvent. Manufacturers literature and standard
handbooks, such as MODERN PLASTICS ENCYCLOPEDIA, as well as the
polymer literature generally, provide information as to the
solubility of the various polymers in selected solvents. KRATON may
be dissolved in toluene, methyl ethyl ketone or cyclohexanone in
concentrations of from 5 percent to 10 percent to form a suitable
lacquer. Upon evaporation of the solvent, only the polymer remains
without loss of its biocompatability characteristics.
The connector elements may be made of any material which can be
conveniently fabricated into the desired shapes. Copolymers of
styrene and butadiene, blended or filled with polyproplene, or
other stiffening material, are convenient since cohesive bonding
usually is more easily accomplished than adhesive bonding.
The foregoing examples, are intended merely to illustrate the
invention and are not limiting. Size, materials and details of
fabrication of plastic and metal catheters and the like are well
known and can be used in conjunction with the teachings of this
patent. The extent and scope of the protection claimed hereunder is
not to be limited to the specific examples set forth hereinbefore,
but only by the scope of the following claims.
* * * * *